Pentair Rainbow 320 Chlorinator Leaking or Not Feeding Tablets? How to Fix It (R171096)

Tablet feeders are the part of the equipment pad nobody thinks about until water is dripping down the side of it. The Pentair Rainbow 320 (part number R171096) shows up on a huge number of residential pools, and when it acts up it usually does one of three things: it leaks, it stops feeding chlorine, or it eats a full load of tabs in a couple of days.

The good news is that the Rainbow 320 is a simple device. There is no circuit board and nothing electrical inside it. Almost every complaint traces back to a gasket, the lid, the control valve, or how the unit was plumbed. Here is how to sort out which one you are dealing with.

Why is my Rainbow 320 chlorinator leaking?

Nine times out of ten a leaking Rainbow 320 is a bad lid o-ring. Chlorine gas is brutal on rubber, and the o-ring under the cap dries out, flattens, and stops sealing.

Take the lid off and look at the o-ring. If it is cracked, squared off instead of round, or has a permanent groove pressed into it, replace it. Do not try to fix a worn o-ring by cranking the lid down harder. That is how people crack the cap.

Other spots to check on the R171096:

• The threads on the lid itself. Hairline cracks are common on older caps and they weep constantly.
• The control valve at the base, which has its own seals that wear out.
• The inlet and outlet fittings, especially if someone used the wrong sealant or overtightened them during install.
• The body of the feeder. A cracked housing is not repairable and means a new unit.

One habit that makes a big difference: lube the lid o-ring with a silicone-based pool lubricant every time you reload tabs. Never use petroleum jelly. It breaks rubber down fast.

Why isn't my chlorinator feeding tablets?

If chlorine is not moving, the usual cause is either no flow through the feeder or tabs that have bridged and stopped dissolving. Both are easy to check.

Start with the dial on top of the control valve. If it is set to zero or it got bumped closed, no water is passing through the tab chamber. Turn it up and see if your chlorine reading recovers over a day or two.

Next, pop the lid and look inside. Tabs sometimes fuse into one solid chunk that wedges above the water line and never gets wet. Break it up and check that the tabs are actually sitting down in the tube. Also confirm you are using slow-dissolve 3 inch trichlor tabs. Fast-dissolve granular or 1 inch tabs behave completely differently in this feeder.

Then look at the plumbing. The Rainbow 320 is designed to be installed after the filter and after the heater, as the last piece before water returns to the pool. If it was plumbed somewhere else, it may not be getting enough pressure differential to pull water through.

Why is my Rainbow 320 burning through tabs too fast?

Usually the dial is open too far, or the control valve seals have worn out and water is bypassing the setting entirely.

Try setting the dial to a low number and testing your free chlorine after a few days. If your chlorine is still climbing past 5 ppm with the valve nearly closed, the valve is not sealing and needs to be rebuilt or the feeder needs to be replaced.

How to service the R171096 step by step

• Shut the pump off and let the system depressurize. This matters. There is chlorine gas trapped in that chamber and it is under pressure.
• Close the control valve dial all the way.
• Turn the lid slowly and stand off to the side. Let the pressure release before you lift the cap.
• Pull the o-ring, clean the groove, and inspect it in good light.
• Wipe out any sludge or undissolved residue at the bottom of the tube.
• Lube the fresh o-ring, seat it, load tabs, and hand tighten the lid only.
• Restart the pump, open the dial a small amount, and watch for drips for a few minutes.

Should you repair or replace the Rainbow 320?

Repair it if the body and lid are solid and the problem is an o-ring or a seal. That is a cheap fix and buys you years.

Replace it if the housing is cracked, the lid threads are stripped, or the control valve keeps leaking after new seals. A whole new R171096 feeder costs less than most people expect, and chasing a failing one with parts usually costs more in the long run. Same answer if the unit is old enough that the plastic has gone chalky and brittle. Chlorine and sunlight do that over time, and once the plastic is degraded, the next crack is just a matter of when.

If you are replacing it, plumb the new Rainbow 320 last in line and add a check valve between the feeder and your heater if there isn't one already. Concentrated chlorine backing up into a heat exchanger is an expensive mistake.

Pentair | R171096 | Rainbow 320 In-Line Automatic Chlorinator | Model 320 Tablet Feeder

$125.00

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