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

The Rainbow 320 is one of those parts nobody thinks about until there's a puddle under the equipment pad or the chlorine reading drops to nothing. It sits quietly on the return line doing its job for years, then starts acting up.

Good news: most Rainbow 320 problems come down to three or four cheap parts. Here's how to tell what's actually wrong with your R171096 before you replace the whole feeder.

What does the Pentair Rainbow 320 actually do?

The Rainbow 320 is an in-line automatic chlorinator. You load 3 inch chlorine tabs into it, water flows through a portion of the housing on its way back to the pool, and the tabs slowly dissolve into that stream.

A control knob on the lid opens and closes the flow path so you can dial the feed rate up or down. Because it is plumbed in-line (permanently installed after the filter and heater), everything that goes wrong with it tends to show up as either a leak or a chlorine problem.

Why is my Rainbow 320 leaking?

Almost every Rainbow 320 leak comes from the lid o-ring, the control knob assembly, or a cracked housing. Look at where the water is actually coming from before you buy anything.

• Water seeping out from under the lid. That's the lid o-ring. It dries out, flattens, and stops sealing. This is the single most common R171096 leak.
• Drip coming from the knob itself. The control valve o-rings are worn. There's a small internal seal set that handles this.
• Water coming from the body of the unit. That's usually a crack, and cracks in a chlorinator housing are not worth patching. Chlorine gas and old plastic do not get along.
• Leaking at the pipe unions. Check the union o-rings first. Also make sure nobody overtightened the union nuts with a wrench, which splits them.

Before you replace anything, shut the pump off, close the isolation valves if you have them, and let pressure bleed off. Never open a chlorinator lid with the system running.

Why isn't my Rainbow 320 feeding chlorine?

If your chlorine is at zero but the feeder still has tabs in it, the most likely cause is a blocked or fully closed flow path. Start with the knob setting, then work down.

• The control knob got bumped to zero, or somebody closed it last season and never reopened it.
• The tabs have compacted into one solid brick at the bottom. This happens when the feeder sits dry for weeks and then gets wet again.
• Calcium and tab residue have plugged the outlet port or the check valve.
• Flow through the return line is low, so not enough water is being diverted through the feeder. A dirty filter or a pump running at too low a speed will do this.
• You're using the wrong tabs. Only 3 inch trichlor tabs belong in a Rainbow 320. Cal hypo tabs in a trichlor feeder is a genuinely dangerous mix.

How do you unstick a Rainbow 320 lid?

A stuck lid is almost always chlorine residue welding the threads together, not a broken part. Warm water and patience beat brute force here.

With the pump off and pressure released, pour warm (not hot) water over the lid ring to soften the buildup. Then turn the lid counterclockwise with steady even pressure using both hands. If it still will not budge, a strap wrench spread across the lid works better than channel locks, which crack the plastic. Once it's open, wipe the threads clean and put a thin coat of silicone lubricant on the o-ring so it does not happen again.

How to reload and reset the R171096 the right way

1. Turn off the pump and let the system depressurize completely.
2. Close the isolation valves on either side of the feeder if your plumbing has them.
3. Slowly unscrew the lid, standing back so the gas that built up inside vents away from your face.
4. Remove any broken tab pieces and sludge at the bottom. Rinse the housing with fresh water.
5. Inspect the lid o-ring. If it's flat, cracked, or chalky, replace it. Lubricate it with silicone, never petroleum jelly.
6. Load fresh 3 inch tabs, hand tighten the lid, reopen the valves, and restart the pump.
7. Set the knob low (around 1 or 2) and test your chlorine after 24 hours before turning it up.

Repair the Rainbow 320 or replace it?

Rebuild it if the housing is solid and the problem is a seal, a knob, or a plugged port. Replace the whole R171096 if the body is cracked, the threads on the lid seat are chewed up, or the unit is more than about ten years old and starting to leak in more than one spot.

Chlorinator housings get brittle over time from chlorine exposure. Once one section fails, the rest usually is not far behind, and a slow leak on the return line will eat your equipment pad and your water bill at the same time.

Related parts worth having on the shelf

If you run a Rainbow 320, keep a spare lid o-ring and a tube of silicone lubricant on hand. Those two items solve the majority of R171096 service calls. A replacement lid and a control valve rebuild kit are the next most common parts people need.

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

$125.00

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