What is this other port (capped off) and cover for in my skimmer drain?

Apr 6, 2016
329
Louisiana
I've circled them in blue. Obviously the open one is the piping to the skimmer sunction, but what is the other one for? It is capped off and has been caulked around. Should it be? I noticed the caulking is a little thin on 2 of the sides, could this cause a suction side air leak (I have a small air leak somewhere that is causing some bubbles to come out my 3 pool return jets, haven't been able to figure out where though). Should I put some new caulking around it? Also, what's the flap for?
 
Don't see the picture but for skimmers that have 2 holes the second is for an equalizer ( suction port just below the skimmer) or to be plumbed to the main drain if the drain does not have a dedicated line. Just depends on the builder if they use it or not. If they did not use it plugged and or calked is normal. If it does go to the Main drain the flap is to adjust the amount of suction to the MD vs the skimmer. The MD does not need much if any suction some people close it completely to divert all flow for maximum skimming.

Edit: If it doubtfull it would cause a suction side leak (air in the pump basket) because it is under water. If there was a leak in the MD line I could see the previous owner plugging both the MD and that port to prevent water loss but again that assumes the MD does not have a dedicated line
 
Yup that is exactly what I was describing, I doubt it is causing any problems you could put some putty around it but probably not needed. Most suction leaks are from the pump lid, check that there is no debris under the gasket and use some silicone lube for pool gaskets you can get it at pool stores or Amazon.
 
Yup that is exactly what I was describing, I doubt it is causing any problems you could put some putty around it but probably not needed. Most suction leaks are from the pump lid, check that there is no debris under the gasket and use some silicone lube for pool gaskets you can get it at pool stores or Amazon.

Thanks for explaining all that. I've recently bought a new clamp lid and o-ring for the pump basket, but it is still producing bubbles out of my return jets. The only other thing I could think of is that may be causing the air leak is that the clamp doesn't FULLY engage when screwed on. It gets tight, but stop about 1/2-3/4 of the way. You can see part of the ledge/lip (about an inch) still sticking out (on all 4). I believe the receiver part of the pump basket (the part on the actual pump itself that the clamp screws onto) is slightly warped causing it not to screw on completely. Could this be the problem? I've even thought about taking the old lid and sanding down the 4 lips a little, so that I'd be able to fully close the clamp. What you think?
 
you can usually prove/disprove a suction leak at the lid by pouring water over the lid while the pump is running the water slowly being poured over will actually seal the leak and the bubbles will stop. If you do a YouTube search there are at least a couple of videos on it. If the old lid does not work any better than the new sounds like you don't have a lot to loose by trying to alter the old one just be careful not to get it permanatily stuck.
 
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