If an inline chlorinator isn’t working, first determine whether the tablets stopped dissolving or the pool simply has low chlorine. Those are different problems. Unchanged tablets suggest a delivery issue, while disappearing tablets with low chlorine can indicate excessive demand or an inadequate feed schedule.
Confirm the pool’s free chlorine with a suitable test before changing equipment. Maintain sanitation with an appropriate labeled backup treatment while investigating. Don’t leave the pool untreated while waiting to see whether another tablet dissolves.
Identify the actual feeder
Find the model on the body or cap and obtain its manual. An external tube doesn’t necessarily mean the unit is an offline feeder. The Pentair Rainbow320, for example, is inline but includes a small feed tube.
Note whether the feeder sits above or below pool water level. Service procedures can differ for those installations. Don’t apply a refill or inspection sequence from a photograph of another model.
Also identify the chemical already inside. Only use the type approved for that feeder. Never add shock, liquid chlorine, acid, or calcium hypochlorite to a trichlor chamber to “clear” a blockage.
Separate three common patterns
| Pattern | Start here |
|---|---|
| Tablets barely change and free chlorine falls | Effective flow, valve setting, screen, and check valve |
| Tablets dissolve but free chlorine remains low | Demand, operating hours, stabilizer, and test accuracy |
| Feed changes after a pump or plumbing adjustment | Actual speed schedule and installation geometry |
There is no universal number of days a tablet must last. Tablet size, approved formulation, water temperature, exposure, and flow all matter. A calendar estimate alone doesn’t prove the feeder is blocked.
Look for a change from the system’s own previous behavior under similar conditions. If the same setup suddenly stops feeding, inspect recent maintenance and small components. If it has never fed properly, installation and sizing deserve more attention.
Check ordinary circulation first
Confirm that the pump is primed and the pool’s circulation path is open. Check baskets and filter condition using their normal service procedures. A pump can sound active while delivering inadequate water through the intended path.
Review the actual timer and speed schedule. A variable speed pump may provide adequate feeder flow at high speed but insufficient delivery during the longer low speed period. Test the system under the program you intend to use every day.
Don’t close return valves randomly to force more water into the feeder. That can create other pressure and circulation problems. Use the manufacturer’s flow requirements and have an installer assess a layout that doesn’t meet them.
Confirm the control valve does what you expect
Check that the feeder valve is not closed and that the handle is correctly attached. A loose or misindexed handle can make the printed number misleading. Follow the manual before removing or repositioning it.
Make a modest documented adjustment and evaluate chlorine delivery over the appropriate interval. Turning immediately to maximum can create overchlorination once flow is restored. The dial is a feed adjustment, not a direct chlorine concentration setting.
If changing the dial has no effect, investigate the feed path. More tablets won’t fix a closed or obstructed water route. Use the specified inspection procedure rather than opening the lid during operation.
Don’t diagnose from chamber water level alone
Some feeders are designed to lower their internal water level when the pump stops. A chamber that isn’t full after shutdown may therefore be normal. The expected behavior depends on the model and plumbing height.
Likewise, finding water inside doesn’t prove it is moving through the tablets at a useful rate. Stagnant water and active feed are not the same. Evaluate operation through the approved checks and the water test trend.
Avoid an open lid running test unless it is explicitly part of the correct manufacturer’s procedure for that installation. Concentrated chemical solution and pressure make improvisation unsuitable. Follow the full instructions, including any special below water level requirements.
Inspect the small feed components
After the required shutdown and pressure relief, check accessible tubing for kinks, splits, and deposits. Inspect the model’s screen and check valve as directed. A small restriction can reduce chemical delivery even while the main return flow seems strong.
Use the parts diagram to identify the component before removing it. On a Rainbow320, the internal check valve is not the same item as an external corrosion resistant check valve. Replacing the wrong valve may leave the original problem unchanged.
Don’t remove a check valve permanently to increase flow. It has an operating or backflow function within the design. Clean or replace it only through the specified procedure and with a compatible part.
If the body, cap, or tube fittings are cracked, stop using the feeder until repaired. Avoid overtightening plastic connections or patching a pressure component with household adhesive. Keep the chemical isolated and handled according to the equipment instructions.
Recheck installation after plumbing changes
Some inline designs depend on the flow behavior at their inlet, not simply the main pipe diameter. Nearby elbows, divided pool and spa returns, or a changed pump can affect delivery. Compare the current arrangement with the manual.
The Rainbow320 instructions distinguish several plumbing arrangements and optional flow modifications. Its top feed configuration is not the same as its optional HiFlo supply kit. They address different conditions and should not be treated as interchangeable fixes.
Top feed can increase chemical delivery enough to overchlorinate under ordinary conditions. Don’t move a tube to the upper port just because a forum photo shows it. Follow the model’s sequence and verify the resulting residual.
If tablets dissolve, investigate chlorine demand
Test free chlorine, pH, and stabilizer with suitable methods. Review recent swimming, sunlight, debris, algae, and specialty treatments. A functioning feeder can be overwhelmed by conditions beyond its current delivery rate.
Don’t solve an active algae problem by adding a larger stack of tablets and waiting. Use an appropriate recovery process, then establish the feeder’s maintenance setting. Ongoing trichlor use also adds stabilizer, so reassess the program when that level becomes unsuitable.
If the feeder cannot meet normal demand under a compliant schedule, evaluate capacity or another sanitizer approach. Use pool feeder types and maintenance for the broader decision. A clean, correctly installed feeder can still be the wrong fit for a particular job.
Verify the repair with a short record
Record the repaired component, valve setting, tablet load, and actual pump schedule. Check for leaks during operation and after shutdown. Then follow the chlorine trend under normal use.
The repair is complete when the pool maintains its required residual without unstable dosing. Tablet erosion is supporting evidence, not the final target. Save the model and successful settings so the next diagnosis starts with a useful baseline.
