Can't detect air leak

Mar 29, 2017
Hesperia, Ca
Hey all,

I have an air leak in my filtration system. I believe it's on the suction side and I can't find it. It's so bad I need to prime it in the AM with the hose to fill the pipe back up from the filter basket to get it to run. After that it will run all day. But the next AM it will just run dry. I've checked:

Filter basket o-ring - good
water level - good
vacuum - unplugged that to make sure it wasn't coming in through the hose
DE filter o-ring - good - no leaks

Some thoughts and recent changes in the system to consider:

- Recently I had my pool drained and acid washed and refilled. Seemed to run OK after that.

- Also I replaced the thermister on the heater. It didn't seem to go in as far a the old one, but it works. Is it possible that air can be getting in through that even if the heater is not engaged?

I have a slow water leak out of the pipe coming out of the top of the filter. Could that be the source of air getting in? See pic.

Anyhow I'd love to hear some insight.





Gold Supporter
Apr 25, 2016
Hi Jon,

The pic is of your pump, not a filter. Any water leak is potentially an air leak. Though, most air leaks tend to be suction side. That pic shows a pretty worn/corroded seal. I'd consider replacing that portion of the plumbing and ensuring a good pvc weld before looking for other leak candidates. Starting with the obvious is often the best bet.

Good luck!

Take care,


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

I believe that it is almost a crime to install a pump without the proper unions. :cool:

They look like this.... and have an O-Ring on the threaded side.

Unions will eliminate the problem of leaking joints at the pump input/output....

Thanks for posting.

Jim R.


Gold Supporter
Apr 25, 2016
Hey Jon,

Definitely agree with Jim - the unions cost a little more than pvc-weld fittings, but they definitely a LONG way toward making things serviceable!

How is your progress coming along?



In The Industry
Mar 17, 2015
New Orleans, LA
Check valves in front of the pump. They have o-rings that can go bad Check o-ring on pump lid. Make sure skimmers a full and doors are not stuck up. Your priming problem is air getting in from somewhere in front of pump.
Mar 29, 2017
Hesperia, Ca
OK so all leaks have been fixed except one. I still have a small leak apparently in the seal plate or plate gasket on the pump. It will be fine for a couple days and then one AM it will not prime. The daily schedule is for the vacuum to run first so pump starts at a higher speed for one hour. This AM it wasn't running and no water was flowing. So I started the spa (much higher speed) and after about 30 seconds massive bubbles came out...followed by the jets and water running. Prime was good and the pump worked fine at the lower speeds.

So can this gasket be the cause of my prime being lost? I know it's supposed to be a suction side issue, but this is sort of right in the middle of suction and return sides.


In The Industry
Jul 8, 2010
Ashford, CT
O ring on pump basket.
O rings on plugs on pump side
Main suction connection on front of pump
A union on the front of the pump or general area.
A O ring on a Jandy valve before the pump.

Make sure there is enough water in the pool so its not sucking air from a skimmer.

Then there are seals inside the pump....