Automatic pool chlorinators dispense chlorine tablets through your pool’s circulation system, but the right feeder depends on your plumbing, pool size, and comfort with installation. I rank the Pentair Rainbow 320 as the best overall for buyers seeking an established in-line design, while the Hayward CL200 is a strong alternative for compatible in-line installations and the U.S. Pool Supply 9 lb Off-Line Feeder suits pools where a bypass-style setup is preferable. The main tradeoff is between an in-line feeder’s direct plumbing connection and an off-line model’s separate tubing and installation requirements. Capacity, connection size, replacement parts, and access for refilling also separate these choices. Read on for the full breakdown and guidance on matching a feeder to your pool system.
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Key Takeaways
- In-line versus off-line installation is the first major decision: in-line models join the return plumbing, while off-line feeders use separate connections and tubing.
- The Pentair Rainbow 320 leads the roundup for buyers seeking a familiar in-line feeder design; it is not automatically the best fit if your plumbing cannot accept it.
- The Hayward CL200 and CL200EF are distinct choices, so check the exact model and installation format rather than treating similar names as interchangeable.
- Nine-pound capacity appears across several off-line and in-line options, but a larger tablet chamber does not resolve mismatched plumbing or difficult refill access.
- Compatible and budget-oriented alternatives can make sense, but connection dimensions, included unions, and replacement-part fit deserve closer checking than the product name alone suggests.
| Pentair Rainbow 320 Automatic In-Line Chlorine/Bromine Feeder |  | Best Overall In-Line Feeder | Brand: Pentair | Model: R171096 | Installation: In-line return line | VIEW LATEST PRICE | See Our Full Breakdown |
| Hayward CL200 Automatic In-Line Chlorine and Bromine Feeder |  | Best for Adjustable Feed Control | Brand: Hayward | Model: CL200 | Type: In-line automatic chemical feeder | VIEW LATEST PRICE | See Our Full Breakdown |
| U.S. Pool Supply Off-Line Automatic Pool Chlorine Feeder, 9 lb |  | Best Off-Line Kit for Existing Hayward CL220 Setups | Brand: U.S. Pool Supply | Model: USP CF-479 | Type: Off-line automatic pool chemical feeder | VIEW LATEST PRICE | See Our Full Breakdown |
| XtremepowerUS Offline Automatic Pool Chlorinator Feeder, 9 lb Capacity |  | Best for Above-Ground and Small In-Ground Pools | Model: 90156 | Installation type: Off-line | Capacity: 9 lb | VIEW LATEST PRICE | See Our Full Breakdown |
| Hayward CL200EF Automatic Chlorine Feeder for In-Ground Pools |  | Best for In-Ground Pool Owners Seeking Long Refill Intervals | Brand: Hayward | Model: CL200EF | Type: Automatic chemical feeder | VIEW LATEST PRICE | See Our Full Breakdown |
| Hayward CL220EF Off-Line Chemical Feeder, 9 lb Capacity |  | Best Off-Line Pick | Brand: Hayward | Model: CL220EF | Feeder type: Off-line automatic chemical feeder | VIEW LATEST PRICE | See Our Full Breakdown |
| R171096 Compatible In-Line Chlorine and Bromine Pool Feeder |  | Best for Rainbow 320 Replacements | Model: 320 | Manufacturer part number: R171096 | Tablet capacity: 11 large or 98 small tablets | VIEW LATEST PRICE | See Our Full Breakdown |
| MAYGO Inline Automatic Pool Chlorinator – 1‑1/2″ Internal Thread Connection |  | Best for Adjustable Feed Control | Brand: MAYGO | Model number: CL | Capacity: 9 lb chlorine tablets | VIEW LATEST PRICE | See Our Full Breakdown |
| Swimline Hydrotools 8750 In-Line Automatic Chlorine Feeder |  | Best Replacement-Style In-Line Feeder | Brand: Swimline Hydrotools | Model: 8750 | Feeder type: In-line automatic chlorine feeder | VIEW LATEST PRICE | See Our Full Breakdown |
| ProMotus 9 lb In-Line Pool Chlorinator with 1.5-Inch Unions |  | Best for 1.5-Inch Union Connections | Tank capacity: 9 lb | Pool capacity: Up to 40,000 gallons | Tablet size: 3 inches | VIEW LATEST PRICE | See Our Full Breakdown |
| Pentair Rainbow 300 Automatic Pool and Spa Feeder |  | Best for Enclosed-System Simplicity | Series: 300 | System: Completely enclosed | Venting: No special venting required | VIEW LATEST PRICE | See Our Full Breakdown |
| XtremepowerUS Inline Automatic Pool Chlorinator, 3-Inch Tablets |  | Best for Small Pools with Adjustable Feeding | Model: 90157 | Installation: Inline in the pool water return line | Tablet size: 3 inches | VIEW LATEST PRICE | See Our Full Breakdown |
| U.S. Pool Supply In-Line Automatic Pool Chlorine Feeder, 9 lb |  | Best for Checking Tablet Supply at a Glance | Model: USP CF-478 | Chemical capacity: 9 lb (4 kg) | Compatible chemicals: Slow-dissolving trichlor or bromine tablets or sticks | VIEW LATEST PRICE | See Our Full Breakdown |
| Hayward CL100 Automatic Chlorine Feeder |  | Best for Simple Pool-and-Spa Dosing | Model: CL100 | Tablet diameter: 3 inches | Flow rate: 50 gpm | VIEW LATEST PRICE | See Our Full Breakdown |
| R171096 Automatic In-Line Pool Chlorinator, Compatible with Pentair Rainbow 320 |  | Best High-Capacity Replacement Feeder | Model: R171096 | Compatibility: Pentair R171096 and Rainbow 320 | Material: ABS plastic | VIEW LATEST PRICE | See Our Full Breakdown |
| automatic pool chlorinator | Model | Material |
|---|---|---|
| Pentair Rainbow 320 Automatic | R171096 | — |
| Hayward CL200 Automatic In-Lin | CL200 | — |
| U.S. Pool Supply Off-Line Auto | USP CF-479 | ABS plastic |
| XtremepowerUS Offline Automati | 90156 | Heavy-duty resin |
| Hayward CL200EF Automatic Chlo | CL200EF | — |
| Hayward CL220EF Off-Line Chemi | CL220EF | — |
| R171096 Compatible In-Line Chl | 320 | — |
| MAYGO Inline Automatic Pool Ch | — | ABS |
| Swimline Hydrotools 8750 In-Li | 8750 | — |
| ProMotus 9 lb In-Line Pool Chl | — | ABS |
| Pentair Rainbow 300 Automatic | — | — |
| XtremepowerUS Inline Automatic | 90157 | Heavy-duty resin |
| U.S. Pool Supply In-Line Autom | USP CF-478 | ABS plastic |
| Hayward CL100 Automatic Chlori | CL100 | Plastic |
| R171096 Automatic In-Line Pool | R171096 | ABS plastic |
More Details on Our Top Picks
Pentair Rainbow 320 Automatic In-Line Chlorine/Bromine Feeder
The Pentair Rainbow 320 is the most versatile in-line choice here for owners who want one feeder for a pool or spa. Its capacity of 11 large or 98 small tablets can reduce refill frequency, while adapters accommodate either 2-inch or 1.5-inch connections. It also accepts slow-dissolving trichlor or bromine tablets and needs no special venting. Compared with the Hayward CL200, the Rainbow 320 makes its plumbing fit and tablet capacity especially clear, though the Hayward specifies an adjustable feed-rate dial. The main installation catch is that unions are not included, so buyers may need to source those separately. This pick suits people with compatible return-line plumbing who value broad pool-and-spa use over an explicitly stated adjustment dial.
Pros:- Works with pools and spas and accepts trichlor or bromine tablets
- Holds up to 11 large or 98 small tablets
- Includes adapters for 1.5-inch connections alongside 2-inch slip PVC
- Requires no special venting
Cons:- Unions are not included
- No adjustable feed-rate control is specified in the provided product details
Best for: Pool and spa owners with compatible return-line plumbing who want a high-capacity feeder that accepts chlorine or bromine tablets.
Not ideal for: Buyers seeking a complete union-equipped installation kit or a model with a clearly specified adjustable feed dial.
- Brand:Pentair
- Model:R171096
- Installation:In-line return line
- Compatibility:Pools and spas
- Fitting:2-inch slip PVC with adapters for 1.5-inch connections
- Tablet capacity:11 large or 98 small tablets
- Compatible tablets:Bromine or slow-dissolving trichlor
- Warranty:1 year
- Unions:Not included
Our verdict“Choose the Rainbow 320 if you want a high-capacity in-line feeder for a pool or spa and can supply the missing unions.”
Hayward CL200 Automatic In-Line Chlorine and Bromine Feeder
The Hayward CL200 suits owners who want to tune tablet delivery with an adjustable feed-rate dial rather than rely only on routine tablet replacement. Its ABS body and Viton seal are specified as corrosion-resistant, and it feeds slow-dissolving trichlor or bromine through a pool or spa pump-and-filter system. That makes it a more control-focused alternative to the Pentair Rainbow 320, which spells out a larger tablet capacity and plumbing adapters but not a feed dial in the supplied details. The CL200 depends on a compatible pump and filter, so it is not a standalone option for every plumbing layout. Tablet capacity and connection dimensions are also not provided here, leaving fit and refill planning less clear than with the Rainbow 320.
Pros:- Adjustable dial gives control over chemical feed rate
- Accepts slow-dissolving trichlor or bromine tablets
- Corrosion-resistant ABS body
- Viton seal is specified
Cons:- Requires a compatible pool or spa pump-and-filter system
- Tablet capacity and plumbing connection dimensions are not specified in the provided details
- Tablets are not included in the provided product details
Best for: Pool or spa owners with a compatible pump-and-filter system who want a dial to adjust chlorine or bromine feed.
Not ideal for: Buyers who need stated tablet capacity or connection details before choosing, or who do not have compatible circulation equipment.
- Brand:Hayward
- Model:CL200
- Type:In-line automatic chemical feeder
- Compatible tablets:Slow-dissolving trichlor or bromine
- Feed control:Adjustable dial
- Body material:ABS
- Seal material:Viton
- System requirement:Compatible pool or spa pump-and-filter system
Our verdict“Pick the CL200 if dial-based feed adjustment matters more to you than the Rainbow 320’s stated capacity and adapter details.”
U.S. Pool Supply Off-Line Automatic Pool Chlorine Feeder, 9 lb
The U.S. Pool Supply USP CF-479 is the most installation-kit-oriented option in this group: it includes a PVC hose, clamp, gasket, PTFE tape, lid wrench, and other installation accessories. Its 9 lb capacity, dial control, and transparent lid make refill planning more straightforward than on the Hayward CL200, whose supplied details do not state a capacity or include comparable accessory information. The clearest fit is an off-line setup compatible with the Hayward CL220 chlorinator; that specific compatibility is also a limitation, not a promise of universal fit. The lid lets owners check contents without opening the feeder, but tablets or sticks are sold separately. Choose it when the included fittings and visible contents matter more than broad, unspecified compatibility.
Pros:- 9 lb capacity supports longer intervals between refills
- Dial control adjusts the chemical feed rate
- Transparent lid allows contents checks without opening the unit
- Includes PVC hose, clamp, gasket, PTFE tape, lid wrench, and installation accessories
Cons:- Compatibility is specifically identified with the Hayward CL220 chlorinator
- Tablets and sticks are sold separately
Best for: Owners with a compatible Hayward CL220 off-line setup who want a 9 lb feeder and a bundle of installation accessories.
Not ideal for: Pool owners who need a broadly specified universal fit or expect tablets and sticks to come with the feeder.
- Brand:U.S. Pool Supply
- Model:USP CF-479
- Type:Off-line automatic pool chemical feeder
- Chemical capacity:9 lb (4 kg)
- Compatible chemicals:Slow-dissolving trichlor chlorine or bromine tablets or sticks
- Feed control:Dial control valve
- Material:ABS plastic
- Compatibility:Hayward CL220 chlorinator
- Included accessories:PVC hose, clamp, gasket, PTFE tape, lid wrench, and installation accessories
Our verdict“Choose this feeder for a compatible CL220 installation when its included accessories and see-through lid are more useful than broader fit claims.”
XtremepowerUS Offline Automatic Pool Chlorinator Feeder, 9 lb Capacity
For an above-ground or small in-ground pool, the XtremepowerUS 90156 offers an off-line layout that avoids placing the feeder directly in the main return line. Its dial adjusts delivery, and the 9 lb heavy-duty resin tank holds 3-inch slow-dissolving chlorine or bromine tablets. The stated maximum pressure is 50 PSI, useful as a compatibility check when comparing plumbing requirements. Unlike the U.S. Pool Supply USP CF-479, this model is described for a pool type rather than a named Hayward CL220 setup, but its product details do not list installation accessories. It is also explicitly aimed at smaller pools, so owners of larger systems should not assume this is the right capacity or application. Tablets are separate.
Pros:- Off-line installation avoids placing the feeder directly in the main return line
- Dial knob adjusts tablet feed rate
- Heavy-duty resin tank holds up to 9 lb
- Accepts chlorine or bromine tablets up to 3 inches
Cons:- Specified for above-ground and small in-ground pools
- Tablets are sold separately
- Installation accessories are not listed in the provided product details
Best for: Owners of above-ground or small in-ground pools who want an off-line feeder with a dial and a 9 lb tank.
Not ideal for: Owners of large in-ground pools, or buyers who need installation accessories included or compatibility confirmed for a specific plumbing system.
- Model:90156
- Installation type:Off-line
- Capacity:9 lb
- Tablet size:Up to 3 inches
- Control:Dial knob
- Maximum pressure:50 PSI
- Material:Heavy-duty resin
- Compatible pools:Above-ground and small in-ground pools
Our verdict“Choose the XtremepowerUS 90156 for a smaller pool when you want off-line installation and a 9 lb tablet tank.”
Hayward CL200EF Automatic Chlorine Feeder for In-Ground Pools
The Hayward CL200EF is aimed squarely at residential in-ground pools, with an off-line plumbing configuration and room for up to 9 lb of chlorine tablets. That capacity and its adjustable dial can reduce hands-on dosing while letting owners regulate output. Compared with the XtremepowerUS 90156, which is described for above-ground and small in-ground pools and accepts bromine as well, the CL200EF makes a more specific case for residential in-ground use but lists chlorine tablets only. Its product details call the feeder in-line in one field while specifying off-line plumbing for installation, so buyers should verify the actual connection arrangement before purchase. No included tablets or fittings are stated, and compatibility with an existing system needs checking.
Pros:- 9 lb capacity can reduce how often tablets need replenishing
- Adjustable dial regulates chlorine output
- Chemical-resistant housing is suited to feeder use
- Described for residential in-ground pools
Cons:- Installation is specified as an off-line plumbing configuration, which buyers should verify against their setup
- Product details specify chlorine tablets, not bromine
- Tablets and installation fittings are not stated to be included
Best for: Residential in-ground pool owners who want an adjustable off-line chlorine feeder with a 9 lb tablet capacity.
Not ideal for: Above-ground pool owners, bromine users, or buyers who need installation fittings and system compatibility clearly confirmed.
- Brand:Hayward
- Model:CL200EF
- Type:Automatic chemical feeder
- Capacity:Up to 9 lb of chlorine tablets
- Installation:Offline plumbing configuration
- Pool type:Residential in-ground pools
- Feed control:Adjustable control dial
- Housing:Chemical-resistant
Our verdict“Pick the CL200EF if you have a residential in-ground pool and want an adjustable 9 lb chlorine feeder after confirming its off-line fit.”
Hayward CL220EF Off-Line Chemical Feeder, 9 lb Capacity
The Hayward CL220EF is the better fit when a pool’s plumbing layout calls for an off-line feeder rather than a unit installed directly in the return line. Its 9 lb capacity accommodates tablets or sticks, while the enclosed ABS body and Viton seal are designed to contain chemical fumes and resist seal wear. The Easy Lok cover makes routine refills more direct, and this model does not require special venting. Compared with the in-line Swimline Hydrotools 8750, it avoids placing the feeder body directly in the main plumbing run, but it does require a compatible off-line hookup. That installation constraint is the main tradeoff: buyers with an established in-line setup may find the Hydrotools or another in-line unit a more straightforward match. It suits pool owners who specifically need an off-line arrangement, not shoppers seeking a universal plumbing fit.
Pros:- 9 lb capacity accepts tablets or sticks
- Enclosed ABS body is designed to help contain fumes
- Easy Lok cover provides convenient refill access
- No special venting is required
Cons:- Off-line installation may not suit the existing plumbing layout
- The provided specifications do not state a pool-volume rating
Best for: Owners of in-ground or above-ground pools whose plumbing setup calls for an off-line feeder with a covered, easy-access tablet chamber.
Not ideal for: Pool owners looking for a direct in-line replacement or whose plumbing does not accommodate an off-line installation.
- Brand:Hayward
- Model:CL220EF
- Feeder type:Off-line automatic chemical feeder
- Capacity:9 lb
- Item weight:4 lb
- Body material:ABS
- Seal material:Viton
- Tablet form:Tablets or sticks
Our verdict“Choose the CL220EF if you need a 9 lb off-line feeder with convenient access; choose an in-line model if your plumbing is built for direct installation.”
R171096 Compatible In-Line Chlorine and Bromine Pool Feeder
This R171096-compatible feeder is aimed at buyers replacing a Rainbow 320-style unit who want to keep using either chlorine or bromine tablets. Its stated capacity of 11 large or 98 small tablets gives buyers flexibility in tablet size, and the included 2-inch PVC accessories and 1½-inch adapters can help match common connection sizes. The maker lists different pool-volume ranges by feed orientation, so buyers should check whether their installation is bottom-feed or top-feed rather than treating the two ratings as interchangeable. Compared with the Hayward CL220EF, this is an in-line option and supports bromine as well as chlorine, but its compatibility is more specific and it calls for monthly cleaning. The widened gasket and upgraded control valve are intended to limit leaks, though they do not remove the need to confirm fit and maintain the feeder.
Pros:- Accepts chlorine or bromine tablets
- Fits up to 11 large or 98 small tablets
- Includes 2-inch PVC accessories and 1½-inch adapters
- Widened gasket and upgraded control valve are designed to improve sealing
Cons:- Compatibility is specified for Rainbow 320 systems
- Monthly cleaning is recommended
- Pool-volume guidance varies by feed orientation and requires checking against the installation
Best for: Pool or spa owners replacing a Rainbow 320-compatible in-line feeder who want to dispense chlorine or bromine in different tablet sizes.
Not ideal for: Buyers with a different feeder format or plumbing system, or owners who do not want to check fit and clean the unit regularly.
- Model:320
- Manufacturer part number:R171096
- Tablet capacity:11 large or 98 small tablets
- Tablet types:Chlorine or bromine
- Bottom-feed pool capacity:6,500–27,000 gallons
- Top-feed pool capacity:18,000–70,000 gallons
- Included fittings:2-inch PVC sliding accessories and 1½-inch adapters
- Compatibility:Rainbow 320 systems
Our verdict“Pick this feeder for a Rainbow 320-style replacement that needs chlorine-or-bromine flexibility, but confirm the fittings and feed orientation before buying.”
MAYGO Inline Automatic Pool Chlorinator – 1‑1/2″ Internal Thread Connection
The MAYGO MG200 stands out for owners who want to tune tablet feed rate at the feeder with a 360° adjustable control knob. Its 9 lb chamber is listed for pools up to roughly 41,000 gallons, putting it close to the ProMotus 9 lb feeder in stated capacity while offering a different connection arrangement. The ABS body and EPDM O-ring are intended to support a sealed installation, but the threading deserves close attention: the listed 2½-inch outer inlet thread and 1½-inch inner outlet thread may not match a Hayward CL200 connection directly. That can add work for anyone unfamiliar with pool plumbing, and the product data specifically notes a connector may be needed. For buyers who can verify the fittings, the adjustable feed offers more hands-on control; those seeking a simpler like-for-like replacement should compare connection details first.
Pros:- 360° knob allows feed-rate adjustment
- 9 lb tablet capacity is listed for pools up to roughly 41,000 gallons
- ABS construction with an EPDM O-ring
- Designed for indoor and ground pools
Cons:- Thread sizes may require a specific connector
- Installation can be more involved for buyers unfamiliar with pool plumbing
- The 41,000-gallon figure is stated as approximate
Best for: Pool owners with plumbing experience who want an in-line 9 lb feeder, adjustable tablet feed, and a stated capacity around 41,000 gallons.
Not ideal for: Buyers seeking a direct Hayward CL200-style connection or a simple installation without checking thread sizes and connector needs.
- Brand:MAYGO
- Model number:CL
- Capacity:9 lb chlorine tablets
- Stated water treatment capacity:Approximately 41,000 gallons
- Inlet thread size:2½ inches outer
- Outlet thread size:1½ inches inner
- Material:ABS
- O-ring material:EPDM
Our verdict“Choose the MAYGO if adjustable feed control matters and you can verify its unusual thread connections before installation.”
Swimline Hydrotools 8750 In-Line Automatic Chlorine Feeder
The Swimline Hydrotools 8750 makes sense for pool owners who want an adjustable in-line feeder built to work with an existing pump and filter system. Its 9 lb capacity and adjustable output cover the core needs of routine tablet feeding, while double-reinforced thermoplastic is described as UV- and corrosion-resistant for poolside conditions. The product is also positioned as a replacement for major brands including Hayward and Pentair, making it a broader alternative to the Rainbow 320-compatible R171096. The tradeoff is that broad replacement language does not confirm a fit for every plumbing configuration, and the supplied information lacks detailed installation instructions. Unlike the off-line Hayward CL220EF, this unit connects to pool plumbing, so it is best for buyers ready to verify an in-line fit rather than those who need an off-line solution.
Pros:- 9 lb capacity with adjustable chlorine output
- Works with the existing pump and filter system
- Reinforced thermoplastic is designed to resist UV exposure and corrosion
- Positioned as a replacement for major brands including Hayward and Pentair
Cons:- Requires connection to pool plumbing
- Detailed installation instructions are not included in the provided product information
- Compatibility still needs to be checked against the pool’s specific setup
Best for: Owners of above-ground or in-ground pools seeking an adjustable 9 lb in-line feeder as a replacement for a compatible major-brand unit.
Not ideal for: Buyers who need an off-line feeder, detailed installation guidance, or assurance that the unit fits a specific plumbing layout without checking.
- Brand:Swimline Hydrotools
- Model:8750
- Feeder type:In-line automatic chlorine feeder
- Capacity:9.0 lb
- Output:Adjustable
- Construction:Double-reinforced thermoplastic
- Pool compatibility:Above-ground and in-ground pools
- Replacement compatibility:Designed as a replacement for major brands including Hayward and Pentair
Our verdict“The Hydrotools 8750 is a practical candidate for a compatible in-line replacement when adjustable output matters more than detailed installation guidance.”
ProMotus 9 lb In-Line Pool Chlorinator with 1.5-Inch Unions
The ProMotus 9 lb feeder is a strong fit for owners who want an in-line chlorinator supplied with two 1.5-inch union adapters. Its chamber takes 3-inch tablets and is rated for pools up to 40,000 gallons, giving buyers a clear capacity target that sits just below the MAYGO’s approximate 41,000-gallon figure. An adjustable dial lets owners change feed rate, while the threaded lid and heavy-duty O-ring support routine refills and sealing. The main catch is installation: this unit uses 1.5-inch external threads, and fitting it may require cutting existing pipes. It also arrives without chlorine tablets, unlike a complete chemical starter kit. Compared with the Swimline Hydrotools 8750, ProMotus gives more explicit fitting details and a stated pool capacity, but buyers should be ready to handle plumbing work and supply their own tablets.
Pros:- 9 lb reservoir holds 3-inch tablets
- Rated for pools up to 40,000 gallons
- Includes two 1.5-inch union adapters
- Adjustable dial valve and O-ring lid support feed control and refills
Cons:- Installation may require cutting pipes
- Chlorine tablets are not included
- 1.5-inch external-thread connection may not match every plumbing setup
Best for: Pool owners with 1.5-inch plumbing who want a 9 lb in-line feeder for 3-inch tablets and can manage a possible pipe modification.
Not ideal for: Buyers seeking a plug-in replacement without plumbing changes or a package that includes chlorine tablets.
- Tank capacity:9 lb
- Pool capacity:Up to 40,000 gallons
- Tablet size:3 inches
- Installation:In-line, 1.5-inch external threads
- Included fittings:Two 1.5-inch union adapters
- Material:ABS
- Maximum pressure:50 PSI
- Flow control:Adjustable dial valve
- Chlorine tablets included:No
Our verdict“Choose ProMotus for its stated 40,000-gallon capacity and included 1.5-inch unions if you can confirm the fit and handle any pipe work.”
Pentair Rainbow 300 Automatic Pool and Spa Feeder
The Rainbow 300 suits buyers who prioritize a fully enclosed feeder and want a system that requires no special venting. That design helps keep feeder gases contained, making it a straightforward choice for pool or spa setups where a venting arrangement is undesirable. Compared with the Hayward CL100, which highlights an adjustable feed rate and access features, the Rainbow 300’s supplied details emphasize containment rather than dosing adjustments or tablet capacity. Its NSF listing is another useful distinction, but the product information does not specify its tablet size or capacity, so I would verify fit and loading expectations before buying. The main installation wrinkle is that unions are not included; buyers may need to source compatible connections separately.
Pros:- Completely enclosed system helps contain feeder gases
- Requires no special venting
- NSF Listed
- Designed for pool and spa use
Cons:- Unions are not included
- Product details do not state tablet size or chemical capacity
- Feed-rate adjustment details are not provided
Best for: Pool and spa owners who value an enclosed, NSF-listed feeder and already know the connection parts their plumbing requires
Not ideal for: Buyers who need unions included, want a stated tablet capacity, or need documented feed-rate controls
- Series:300
- System:Completely enclosed
- Venting:No special venting required
- Unions:Not included
- Certification:NSF Listed
- Intended use:Pools and spas
Our verdict“Choose the Rainbow 300 if an enclosed, no-special-venting design matters more than included unions or clearly stated capacity and controls.”
XtremepowerUS Inline Automatic Pool Chlorinator, 3-Inch Tablets
For an above-ground pool or smaller in-ground setup, this XtremepowerUS feeder combines inline installation with an adjustable feed dial, so water moving through the return line carries the dissolved chemical back into the pool. Its 9-pound tank accepts slow-dissolving 3-inch trichlor or bromine tablets, offering more stated capacity than the Hayward CL100 listing, which does not give a tank capacity. The tradeoff is its intended scale: the maker specifies above-ground and small in-ground pools, not larger in-ground systems. It also needs to be installed after the filter and heater, and tablets are sold separately. I’d choose it over a broadly positioned feeder only when its pool-size fit and return-line layout match the existing system.
Pros:- Adjustable dial provides control over feed rate
- 9-pound capacity for slow-dissolving 3-inch tablets
- Accepts trichlor or bromine tablets
- Heavy-duty resin construction and compatibility with above-ground and small in-ground pools
Cons:- Tablets are not included
- Not intended for larger in-ground pools
- Requires inline installation in the return line after the heater and filter
Best for: Owners of above-ground pools or small in-ground pools who want inline dosing and adjustable feed control for 3-inch tablets
Not ideal for: Owners of larger in-ground pools, or buyers who need tablets included or cannot install a feeder after the filter and heater
- Model:90157
- Installation:Inline in the pool water return line
- Tablet size:3 inches
- Tank capacity:9 lb
- Control:Adjustable dial valve
- Maximum pressure:50 PSI
- Pool compatibility:Above-ground and small in-ground pools
- Material:Heavy-duty resin
- Tablet compatibility:Slow-dissolving trichlor or bromine tablets; not included
Our verdict“Pick this model for a smaller pool with a compatible return line if adjustable feeding and a 9-pound tablet tank are priorities.”
U.S. Pool Supply In-Line Automatic Pool Chlorine Feeder, 9 lb
This U.S. Pool Supply feeder is a practical pick for owners who want a 9-pound inline feeder with a visible chemical level. Its transparent easy-lock cover lets you check the supply without opening the feeder, while the O-ring seal and included lid wrench support routine loading and maintenance. Against the XtremepowerUS 90157, it offers a clearer stated advantage for monitoring the contents and includes installation accessories and instructions; XtremepowerUS, by comparison, specifies a 50 PSI maximum pressure and small-pool fit. This model is compatible with the Hayward CL200, which may help buyers planning around that feeder design, but it is made from ABS plastic and does not include tablets or sticks. Confirm plumbing fit before purchase.
Pros:- 9 lb capacity for slow-dissolving trichlor or bromine tablets or sticks
- Adjustable dial control valve
- Transparent cover makes remaining chemical easy to check
- Includes installation accessories, instructions, and a lid wrench
Cons:- Tablets or sticks are not included
- ABS plastic construction may not suit buyers seeking another material
- Product details do not specify a maximum operating pressure
Best for: Pool owners seeking a 9-pound inline feeder with a see-through cover, adjustable flow, and included setup accessories
Not ideal for: Buyers who want chemicals included, need a feeder with a stated pressure limit, or cannot confirm compatibility with their plumbing
- Model:USP CF-478
- Chemical capacity:9 lb (4 kg)
- Compatible chemicals:Slow-dissolving trichlor or bromine tablets or sticks
- Material:ABS plastic
- Control:Adjustable dial control valve
- Cover:Transparent easy-lock cover with O-ring seal
- Compatibility:Hayward CL200 chlorinator
- Included accessories:Installation accessories, instructions, and lid wrench
Our verdict“Choose this feeder if easy visual checks and included installation accessories matter more than having chemicals or a stated pressure rating in the package details.”
Hayward CL100 Automatic Chlorine Feeder
The Hayward CL100 is a simpler choice for owners who want an automatic feeder connected to a pool or spa pump and filter, with an adjustable feed rate and a threaded cover for tablet access. Its finger-release safety catch adds a specific handling feature not called out for the XtremepowerUS 90157, while that competing model provides a stated 9-pound tank capacity and compatibility with above-ground and small in-ground pools. The CL100’s product details instead specify 3-inch tablets and a 50 gpm flow rate, so buyers should confirm those requirements suit their setup. It can also serve buyers who prefer a relatively straightforward installation, but it depends on a compatible pump-and-filter system and offers no stated chemical capacity.
Pros:- Adjustable feed rate
- Threaded cover provides access for adding tablets
- Finger-release safety catch
- Designed for automatic operation with a pool or spa pump and filter
Cons:- Limited to 3-inch tablets
- Requires a compatible pump-and-filter system
- Product details do not state chemical capacity
Best for: Pool or spa owners with a compatible pump-and-filter system who want adjustable dosing and straightforward access for 3-inch tablets
Not ideal for: Buyers who need a stated large tablet capacity, use tablet sizes other than 3 inches, or lack a compatible pump and filter
- Model:CL100
- Tablet diameter:3 inches
- Flow rate:50 gpm
- Material:Plastic
- Installation style:Above ground
- Dimensions:16 x 8 x 8 inches
- Power source:AC, AC/DC
- System requirement:Compatible pool or spa pump and filter
Our verdict“The CL100 makes sense for pool and spa owners with compatible plumbing who value adjustable feed and straightforward tablet access over a stated high-capacity tank.”
R171096 Automatic In-Line Pool Chlorinator, Compatible with Pentair Rainbow 320
For a larger pool or a replacement project, this R171096-compatible feeder leads the lineup on stated tablet capacity: it holds up to 11 large or 98 small tablets and is specified for pools from 6,500 to 70,000 gallons. That makes it a stronger fit for buyers who want fewer refills than the 9-pound XtremepowerUS 90157 or U.S. Pool Supply feeder, though their capacities are expressed differently and should not be treated as directly equivalent. Its adjustable flow valve, ABS body, drain plug, and included fittings support installation and upkeep. The key limitation is compatibility: this is a replacement for Pentair R171096 and Rainbow 320 feeders, not a universal inline choice. I’d confirm both feeder model and plumbing dimensions before ordering.
Pros:- Capacity of up to 11 large or 98 small tablets
- Adjustable flow control
- Includes 2-inch PVC slip fittings and 1.5-inch adapters
- Drain plug and closed design support maintenance and reduce direct contact with tablets
Cons:- Compatibility is specified for Pentair R171096 and Rainbow 320 feeders
- Buyers must match the listed fittings to their plumbing
- ABS plastic construction may not meet preferences for another material
Best for: Owners of pools within the stated gallon range replacing a Pentair R171096 or Rainbow 320 feeder who want high tablet capacity
Not ideal for: Buyers with a different feeder model or plumbing connection, or anyone seeking a universal replacement without checking fit
- Model:R171096
- Compatibility:Pentair R171096 and Rainbow 320
- Material:ABS plastic
- Tablet capacity:Up to 11 large or 98 small tablets
- Pool size range:6,500–70,000 gallons
- Flow control:Adjustable
- Installation fittings:2-inch PVC slip fittings and 1.5-inch adapters
- Warranty:12 months
Our verdict“Choose this model for a compatible Pentair replacement setup when high tablet capacity and included connection fittings matter more than universal fit.”
How We Picked
I ranked these automatic pool chlorinators by how well their feeder style, connection format, and stated capacity fit common pool setups. I gave priority to clear installation distinctions—especially in-line versus off-line designs—and to details that affect routine use, such as refill access and whether unions or separate tubing are part of the setup. Compatibility matters as much as capacity: a feeder is a poor match if its plumbing connections do not suit the pool’s return line.
The ranking favors recognizable, clearly specified options with a defined role, then distinguishes alternatives by the needs they serve. The Pentair Rainbow 320 leads as a broadly useful in-line pick; the Hayward CL200 and off-line feeders rank for different installation needs rather than as direct substitutes. Compatible replacement-style models and products with less clearly differentiated fit rank lower because buyers may need to verify dimensions, parts, and manufacturer guidance before purchase. I did not treat tablet capacity alone as a proxy for quality or suitability.
| automatic pool chlorinator | Material |
|---|---|
| Pentair Rainbow 320 Automatic | — |
| Hayward CL200 Automatic In-Lin | — |
| U.S. Pool Supply Off-Line Auto | ABS plastic |
| XtremepowerUS Offline Automati | Heavy-duty resin |
| Hayward CL200EF Automatic Chlo | — |
| Hayward CL220EF Off-Line Chemi | — |
| R171096 Compatible In-Line Chl | — |
| MAYGO Inline Automatic Pool Ch | ABS |
| Swimline Hydrotools 8750 In-Li | — |
| ProMotus 9 lb In-Line Pool Chl | ABS |
| Pentair Rainbow 300 Automatic | — |
| XtremepowerUS Inline Automatic | Heavy-duty resin |
| U.S. Pool Supply In-Line Autom | ABS plastic |
| Hayward CL100 Automatic Chlori | Plastic |
| R171096 Automatic In-Line Pool | ABS plastic |
Factors to Consider When Choosing Automatic Pool Chlorinators
Before choosing a feeder, start with your pool’s circulation layout and maintenance routine, not a capacity number. These factors can help you avoid buying a chlorinator that is awkward to install or poorly matched to the rest of your system.
Match the feeder style to your plumbing
An in-line feeder is installed directly into the return plumbing, so it can be a tidy choice when the layout and pipe dimensions support it. An off-line feeder connects through separate inlet and outlet lines, which may suit an existing system that can accommodate that arrangement. Do not assume either style is a simple swap for the other: their plumbing requirements differ. Check the installation manual and measure the intended connection points before ordering. A mismatch can mean added plumbing work, adapters, or a return rather than a straightforward installation. If you are unsure how the feeder will affect the circulation system, ask a pool professional to review the layout.
Verify dimensions, unions, and included connections
Product titles can describe a connection size or compatibility, but those claims do not replace checking the actual fittings. Compare the feeder’s specified connection type with your pipe size, existing unions, and available space. Unions can make later removal easier, but only when their dimensions match the plumbing and the parts are included or readily sourced. Compatible replacement-style feeders also call for careful checking: confirm the precise model they are intended to fit and which original parts they reuse. A common mistake is buying from a familiar model name without checking the connection details. When product information leaves a critical measurement unclear, consult the manual or seller before committing.
Choose capacity around your routine, not a promise of long intervals
A larger tablet chamber can reduce how often you refill, but it does not set a guaranteed schedule. Pool volume, water temperature, sunlight, use, circulation, and desired chlorine level all affect consumption. Capacity is a convenience factor, not a substitute for testing pool water and adjusting your sanitation routine. Think about how often you want to inspect and replenish the feeder, and whether its lid is accessible where it will be installed. Avoid filling a unit and assuming the pool will stay balanced without regular checks. Follow the feeder and tablet instructions, and keep tablets stored and handled as directed.
Plan for safe servicing and refill access
Feeders handle concentrated pool chemicals, so installation and servicing deserve more attention than a simple container refill. Look for a setup that leaves practical access to the lid and lets you follow the manufacturer’s instructions for isolating and opening the unit. Do not open a pressurized feeder or mix different chemical products; follow the manual’s shutdown and handling steps. Accessible placement makes routine maintenance easier and can reduce the temptation to rush servicing. Also check whether the chosen location exposes the feeder to conditions the manufacturer warns against. If you cannot service it safely in the proposed spot, plan a different location before installation.
Decide when paying for a more established fit is worthwhile
A higher-spec or established-brand option can be worthwhile when its parts, instructions, and exact plumbing fit are easier for you to verify. That does not make every branded feeder a better purchase for every pool: a simpler alternative may suit a compatible installation just as well. Compare the whole ownership picture, including unions, tubing, replacement parts, maintenance access, and the effort needed to install it. For a replacement, matching the old feeder’s model and connections may matter more than moving to a larger capacity. For a new installation, favor clear documentation and a known fit over a feature that does not address your setup. If installation labor or adapters are needed, factor those into the decision too.
Frequently Asked Questions
Should I choose an in-line or off-line automatic pool chlorinator?
Choose based on your return plumbing and installation constraints, not on a general claim that one style is better. An in-line feeder is integrated into the return line, while an off-line model uses separate connections and tubing. Check the product’s required pipe size, fittings, and installation instructions against your existing layout. If changing the return line would be difficult, an off-line design may be more practical, provided its hose connections can be installed correctly. When neither setup is clear from the documentation, get a pool professional to check compatibility before buying.
Can I replace my existing feeder with a compatible R171096 model?
Possibly, but the compatibility claim alone is not enough to confirm a direct replacement. Compare the exact feeder model, connection dimensions, lid and body arrangement, and any parts the new unit expects you to reuse. Also check whether your installation is in-line and whether the replacement includes the fittings you need. A product described as compatible with a particular feeder may still require a separate part or a plumbing adjustment. Match the manufacturer’s specifications to your existing setup before removing the old unit.
Is a 9 lb feeder a better choice than a smaller-capacity model?
Not automatically. A larger chamber may mean fewer refills for a particular pool and routine, but it does not tell you how quickly tablets will be used or how long a fill will last. Consumption varies with pool conditions and chlorine demand, so regular water testing remains necessary. Also weigh the feeder’s physical size and refill access against the convenience of extra capacity. If a smaller model fits your plumbing and is easier to maintain, the larger capacity may offer little practical benefit.
Can I use a chlorine feeder with bromine tablets?
Only use the chemical type specified as compatible by the feeder manufacturer and follow the tablet label and equipment instructions. Some listed feeders are described for chlorine and bromine, while others are identified specifically as chlorine feeders. Do not assume that a feeder’s ability to hold tablets makes every chemical interchangeable. Never mix different chemicals in a feeder or combine leftover tablets with a new chemical type. If you are changing from one sanitizer to another, check the manufacturer’s cleaning and changeover directions first.
What should I check before installing a feeder on my pool system?
Confirm the feeder style, pipe size, connection type, required space, and included fittings before beginning. Read the installation manual for placement and servicing requirements, and check that you can safely reach the lid for refills. A feeder must work with the circulation system; do not improvise a connection based only on a product photo or title. If the installation involves cutting plumbing or adding bypass lines, consider professional help. Once installed, follow the manual and keep testing the pool water rather than relying on the feeder setting alone.
Conclusion
For most buyers with compatible return plumbing, I recommend the Pentair Rainbow 320 as the best overall because it is the clearest all-around in-line choice in this lineup. For a familiar alternative in the same general installation category, the Hayward CL200 is a strong runner-up; buyers who need a separate-line layout should look at the U.S. Pool Supply 9 lb Off-Line Feeder for best value, after checking fittings and setup needs. Beginners should choose the model whose installation instructions and connection requirements they can verify most easily, rather than defaulting to the largest chamber. For a premium or established-brand preference, compare the Pentair and Hayward options against your exact system and parts availability before paying for features you may not need. If you are replacing a specific feeder, prioritize an exact model and connection match; if your plumbing layout is unusual, ask a pool professional to confirm fit before choosing.
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