Main Drain Leak

[JosephW923]

Hello TFP, looking for some help. I have a leak that I have been narrowing down this past week. Losing about an inch a day when system is running, about 1/4 when system not running.

I have it narrowed down to losing water without skimmers running, only when operating the main drain only or system off. Water level below the skimmer so it’s defitnely not the skimmers.

If it was the liner, would there be an equal amount of water lost when system on or off?

That is why I think it is main drain. So can I air lock the main drain And just operate off of the skimmers to isolate it, or should I dive down and plug the main drain? Pool currently isn’t clean so I can’t get down there to plug it right now.

 

[Texas Splash]

I suspect a liner leak would be constant. You can't just close a 3-way at the pad if it's the drain because water can still seep-out from below within that drain itself - if that's what it is. You would have to dive down there and plug it to confirm. You may have a hydrostatic valve in there and that might be something that needs to be checked as well.

 

[JosephW923]

I suspect a liner leak would be constant. You can't just close a 3-way at the pad if it's the drain because water can still seep-out from below within that drain itself - if that's what it is. You would have to dive down there and plug it to confirm. You may have a hydrostatic valve in there and that might be something that needs to be checked as well.

Ok thanks.
After all the testing I think it’s 99% narrowed down to main drain. After running the system for 12 hours just on skimmers, I am losing the same amount that I lose when The system is off for 12 hours. Which I think would tell me it’s not the returns either.
What does the main drain look like under that cover, is the cover just fit onto the end of PVC pipe? Will I be able to put a rubber stopper plug in there and leave it long term? Maybe until I have to replace the liner to fix the main.

 

[Texas Splash]

What does the main drain look like under that cover, is the cover just fit onto the end of PVC pipe? Will I be able to put a rubber stopper plug in there and leave it long term? Maybe until I have to replace the liner to fix the main.

Pools might vary a bit, but you can expect something like this .............