Odd bit of plumbing


New member
Mar 15, 2019
Jacksonville FL
I was wondering if anyone has run across this before.

Recent house purchase with an in ground pool. The far skimmer has what looks like a 1/3" pipe sticking up through and flush with the patio. Whatever it's purpose, it was intentional.

Whenever the pump fires up and is achieving suction a whistling sound starts coming from the pipe and after about 30 seconds we get two or three water geysers pop up. Once that happens everything settles down.

It's helping air in or out of the system and I can't make up my mind which. Even with 100% on the skimmers I can never keep enough suction to hold the vac plate in place and I'm always getting some fine, Misty bubbles in the returns that percolate larger every 10 minutes or so.

I've been tempted to try capping this thing off to see what happens but not knowing why it's there concerns me.



Gold Supporter
Silver Supporter
TFP Guide
Mar 25, 2018
Chandler Arizona
Hi Jax, welcome to TFP. :wave:

Could you post up some pictures of your equipment pad so we can get a better look. Also, fill out your signature area with all your pool equipment information. You can use mine as reference. :cheers:


TFP Expert
Mar 2, 2011
Probably a suction-limiting vent system.

(II) SUCTION-LIMITING VENT SYSTEM - A suction-limiting vent system with a tamper resistant atmospheric opening. Staff interpretation: A suction-limiting vent system is also called an atmospheric vent. It is a pipe teed to the suction side of the circulation system on one end and open to the atmosphere on the opposite end. The pipe is normally full of water equal to the same height as the pool. When a blockage occurs at the main drain, air is introduced into the suction line thus causing the pump to lose prime and relieving the suction forces at the main drain (suction outlet).
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