Unknown (abandoned?) open pipe on suction side


New member
Oct 20, 2020
Philadelphia, PA
Hello TFP community! I'm a new pool owner and a friend suggested I try TFP for any questions/problems. Well, here's my first one...

To give a brief background, when we bought our home in September 2019 we had the pool inspected and the inspector found a minor suction-side leak. I took note of this and when we opened the pool in June 2020, I asked the pool professional we hired to see what he could do to identify and fix the leak. He was confident it was the two old Jandy valves on the suction side, so we had them replaced. That didn't fix the problem entirely, as we were still getting bubbles coming out of our returns. But everything seemed to be working fine and he suggested that we see how things go for a season and then maybe replace the pool pump (which looks older).

During the season, I tried the shaving cream trick on the pump and surrounding seals on the suction side, but couldn't find any leaks.

Here is what the system looks like:


Fast forward to closing a few weeks ago (first week of October 2020). I closed the pool myself using my air compressor. (I used this Swim University video as a guide.) After I had blown out and capped all of the returns and skimmers, I moved on to the main drain. (At this point, I had my Jandy valve set to direct air ONLY to the main drain.) Rather than seeing bubbles come up in the deep end, as I should have, I instead heard air and some water coming from an open pipe in the ground in my filter/pump area.

I had always wondered why this pipe was there, poking out of the ground and uncapped. I do know the previous owner had at one point abandoned at least the old deep-end skimmer pipe and run a new pipe above ground, which I can plainly see. So, I thought maybe this uncapped pipe was another abandoned pipe.

Anyway, I did some critical thinking and decided to try plugging this open pipe to see what happens. Once I did, bubbles started coming up out of the main drain! I then realized that this open pipe is probably the culprit of my suction side leak. It’s also preventing me from (1) blowing out the main drain and (2) creating a vacuum in the main drain pipe for winterizing.

I have no idea how the previous owners (or the pool professionals they hired) were winterizing the main drain if there is this open pipe in the circuit.

In the end, I capped the pipe using a PVC cap and PVC cement. (See picture below.)

MY QUESTION: Is there any reason why I shouldn’t permanently cap this open pipe? I just want to make sure I’m not disrupting any sort of pressure balancing in the system or anything. In my mind, the suction side needs to be a completely closed system, with no open pipes to suck in air.



Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Good detective work. The pool plumbing on both the suction and return side need to be a closed system to properly function. Cap the open pipe off.