Pool Filter Air Relief Valve Leaking or Stuck? How to Fix It (Replaces Pentair 98209803)

The air relief valve is the little knob on top of your filter tank. Nobody thinks about it until it starts dripping on the pad, spits water in your face, or refuses to bleed air at all. Good news: it is one of the cheapest parts on your whole equipment pad, and swapping a Pentair 98209803 style valve takes about ten minutes.

Here is what goes wrong with these valves, how to tell which problem you have, and how to replace one without breaking anything else.

What does the air relief valve actually do?

It lets trapped air escape from the top of the filter tank so the tank can fill all the way with water. Air gets in every time you open the filter, and it also collects when the pump sucks air through a leaky lid or a low water level.

If that air stays in there, your filter pressure reads wrong, flow drops, and in a bad case the pressure can build up in a way that is genuinely dangerous when you go to open the lid. So a working relief valve is a safety part, not just a convenience.

Why is my pool filter air relief valve leaking?

Almost every leak comes down to a worn o-ring or a cracked plastic body. Sun and pool chemicals slowly harden the rubber, and the plastic gets brittle after a few seasons of UV exposure.

Common causes of a leaking valve:

• The o-ring on the valve stem is flattened, dried out, or missing
• The valve body has a hairline crack from being overtightened
• Grit or DE powder is stuck on the sealing surface, so it never fully closes
• Someone cranked the knob shut with pliers and stripped the threads
• The valve was left partly open after the last cleaning

If water sprays out sideways while the valve is closed, that is usually a cracked body. If it just weeps slowly, try cleaning and lubricating the o-ring first. If that does not stop it, replace the valve.

Air relief valve won't release air? Here's what's usually wrong

When you open the knob and nothing comes out, the passage is plugged. Calcium scale, sand, and DE powder all build up inside that narrow channel over time.

You can sometimes clear it. Shut the pump off at the breaker, back the knob all the way out, and poke the passage with a piece of wire or a paper clip. Rinse it and put it back. If it still will not vent, the valve is done and a new 98209803 style valve is the fix.

One more thing worth checking: if you bleed air and more air keeps coming back every day, the valve is not your real problem. You have a suction side air leak, usually at the pump lid o-ring, the drain plugs, or a loose union.

How to replace the 98209803 air relief valve

This is a simple job. Take your time on step one, because pressure in a filter tank is nothing to play with.

• Turn the pump off at the breaker, not just at the timer
• Open the old relief valve and let all pressure and water bleed off until the gauge reads zero
• Unthread the old valve counterclockwise by hand. If it is stuck, use light pressure with a wrench, and support the filter lid so you do not crack it
• Wipe the threads and the seat clean of old sealant, grit, or scale
• Put a couple of wraps of thread sealant tape on the new valve if the old one had it
• Thread the new valve in by hand until snug. Hand tight plus a small nudge is enough. Do not muscle it
• Turn the pump back on with the new valve open, let the air hiss out, and close it as soon as a steady stream of water appears
• Check the pressure gauge and look for drips for the next few minutes

Which filters does this air relief valve fit?

The high flow valve we stock is built to replace Pentair 98209803 and 98209800, which covers most Pentair cartridge and DE filter tanks that use a threaded top mounted relief valve. Before you order, look at the top of your filter lid and compare the thread size and the shape of the base to the photo.

If you are not sure, send us your filter model number off the label on the tank and we will confirm whether 98209803 is the right part for it.

Repair it or just replace it?

Replace it. At around twenty bucks, a new air relief valve costs less than the o-ring kits and the hour you would spend fussing with the old one. The only time a repair makes sense is if the valve is nearly new and the o-ring is the obvious problem.

While you are up there, it is worth looking at the filter lid o-ring and the pressure gauge too. Both live in the same sun and both fail around the same age. If the gauge needle sits at zero with the pump running, or bounces around, replace it while the system is already drained.

Quick recap

A dripping valve usually means a bad o-ring or a cracked body. A valve that will not vent is usually clogged with scale or DE. Either way, a replacement 98209803 style air relief valve is cheap, and it is one of the few pool repairs you can finish before the water even gets cold.

Appaetech Industries High Flow Air Relief Valve (Replaces 98209803 & 98209800)

$22.00

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