Troubling leak.. 4 in. water loss in 24 hours


Sep 12, 2019
Hello TFP,

This all started with the water autofill making more noise than usual running, and the water levels seemed to have trouble keeping up. With the advise of my local pool company, I was told to shut off the side skimmers lines (two), leave the main drain line open, and let the water drop until it stops going down or its less than 1/4 loss per day. Then to call back for leak detection.

I let the water drop bit by bit over the last few days until it was about under the skimmer then shut the skimmers off to let the main drain stay open.

Since doing that the water has been dropping more rapidly, most recent 24 hours being 4 inches. Other things I've noticed..
1. when pump is turned on after being off for a while, a bunch of air is bubbling through the returns until it becomes only water
2. taking forever for water to come through the maindrain after cleaning the filter yesterday, despite priming, only air would come through at first.
3. today I saw there were chunks of plaster (disturbing) and some small debris in the pump filter basket. When I shut the pump off, the water is reversing into the main drain pipe!

Am I on the right track to suspect this is a maindrain leak vs returns or light areas? Or could it be a hydrostatic valve causing this? Any thoughts?
My next step is to dive down to plug the main drain and check for any hydrostatic valve. If I plug the main drain do I need to "airlock" that or is that just for winterizing scenarios? (I live on a tropical island so not a concern to winterize).

Or... time to get professional help?

Thanks much


  • IMG_2328.JPG
    209.1 KB · Views: 14
  • IMG_2329.JPG
    319.4 KB · Views: 14


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

Gunite pools normally leak at only few places..

Skimmers, Lights, Returns, or Main Drain.

I would do nothing but let it drain until the water is below the lights and/or the returns, whichever is lower.

Where is the water level now???

I had an opportunity to be stationed in Guam or Texas.. I put in for Guam and of course got Texas.. :(


Jim R.


Sep 12, 2019
Thanks for your reply! Texas aint too bad, had to live there for 4 years! But Guam is beautiful just a bit far for most to get to.

I plugged up the main drain, no hydrostatic valves were found, and almost 1 day has passed and barely any water dropped with the bucket test! What a relief! This forum really helped with reading older posts. It seems like I don't really need the main drain.. it should be fine to keep it plugged indefinitely and utilize the skimmers right?
Thread Status
Hello , This is an inactive thread. Any new postings here are unlikely to be seen or responded to by other members. You will get much more visibility by Starting A New Thread