I have a 16,000 gallon inground pool with a fiberglass finish over a gunnite shell. It has a 8-pop up infloor system which has been disabled, so the popups are the only returns. I have a leak somewhere, without the pump running, but I can't seem to find out where.

I plugged both holes (cleaner and main drain) in the poolside skimmer, and the pool is still leaking at a rate of about an 2 inches a day or more. I patched the hole at the pool light conduit, where the power cord enters the pool (in the niche behind the metal pool light assembly, and replaced the gasket on the pool light assembly. Still leaking.

So, I guess that leaves either a main drain leak, Pressure-side pipe leak, or one or more of the infloor pop ups? Squirted some dye around 3 of the pop ups and saw no movement. Any help would be most appreciated. Thanks.

A Quick Update

I drained the pool and inspected the bottom/main 'drain'... which is NOT leaking. I dug up the suction-side PVC from the pool to the pump, and noticed a small drip on the bottom of the PVC at a previous repair connection. But it doesn't trip when the pump is running, and it seems too small a leak to be dropping the pool level by an inch (or two) per day. I continue to suspect the leak is coming from one, or more, of the 8 (disabled) pop-up/return ports on the bottom of the pool. Or, at the T connector under the concrete at the pool edge where it hooks up to the suction line that goes to the pump. The pool is an old Master Pool, and I can't find anything online about the pop-up caps or how to remove them. One photo shows the pool level when the leak appears to slow a bit.

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  • here is a detailed series of answers to your question
    – ojait
    Dec 23, 2020 at 21:21

1 Answer 1


Your leak rate seems to be too slow for the dye tracing method you describe.

You should place temporary patches over any suspect locations and observe which patch gets tightened by water pressure.

Almost any watertight flexible membrane and temporary watertight attachment will do. I would use cut-up garbage bags and duct tape. It only has to last for 24 hours or so.

Be sure to trap a lot of water under each patch when you apply it. The next day, you will find the patch covering the leak has been flattened like a vacuum pack while all the other patches are still blobbing about like happy octopi.

  • 1
    2 inches in a day is too slow? That has to be hundreds of gallons. Could you elaborate?
    – isherwood
    Dec 23, 2020 at 15:28
  • Well, if the pool is 60 feet by 20 feet, it's losing 1496 gallons per day, which is close to 1440 gallons, or 1 gallon per minute. Picture a flow that takes a minute to fill a gallon jug. OP has to detect this from the inside. - A dye squirt could work, or just holding a garbage bag over the suspect location could work. Might depend on how long OP can hold his breath. Dec 23, 2020 at 15:55
  • Professionals use dye tracing and successfully found a much smaller leak (~0.2 in/day) in my pool. Have you actually used the method that you describe, or are you speculating?
    – Mattman944
    Dec 24, 2020 at 9:36

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