Question for in-ground pool owners (water loss)

Could be the in ground plumbing.
Leak detection companies will pressure test for you.

American Leak Detection, I have not used them in a couple of years, but their standard price used to be $400.

Shut pool down. Turn off all valves leading to pool filter. Wait a day. Check water level. If it does go down that much again, it's most likely a leak at your skimmer(s) not underground. Drain pool below the skimmers, let dry for 24 hours, then use sealant and reseal everything.

If that works, great. If not, get a leak detection service.

So if you shut the valves off and the pool doesn't leak, then you likely have a bad seal on the backwash valve. Close your return lines from the pool to the filter and the line going from the filter to the pool. Pull out your backwash valve and replace the O-rings. Use lube and reinstall. You should replace those every few years anyway.

Voice of experience here. Over 25 years with a pool.

Do you know if water is leaking out of your backwash line? The spider gaskets wear out in the multiport valve and you may have a slow leak there.

It could also just be environmental. If it's been particularly windy and/or less humid lately that will cause quicker evaporation.

I'd start with the bucket test first before calling out the leak detection service.

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Pull out your backwash valve and replace the O-rings. Use lube and reinstall. You should replace those every few years anyway.

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Mine was losing water earlier this summer and I figured out it was the spider gasket needing to be replaced. I ordered one and installed a 2" ball valve on the backflow line. I haven't even replaced gasket yet since the ball valve is keep the water from leaking out.

First off thank you all for the tips and the advice, I do appreciate

Well... it does not appear that the water is leaking back through the sand filter via backwash. I disassembled the piping coming out of the sand filter from the backwash, no water has been leaking out of there. Also I have no water leaking from any of the seals or any of the piping, on the pump, or filter

I performed a Dye test in the pool myself, it did not come up with anything leaking that I found.

Could it be that I am just experiencing that much of evaporation? The last few days the water loss has not been consistent, anywhere between 1/4 inch and 3/4 of an inch within a 24-hour. We do live in a very hot and humid climate in south Louisiana and this past week has been extremely humid.

Edit: also thanks to those who provided me with an estimated cost for American Leak Detection. I had no idea how much a leak detection service would cost, so I do appreciate it

I don’t think I have ever lost more than 1/4” in a day before here in south Louisiana under any conditions in 23 years.

We have a gunite pool with spa.

I created a thread a few months ago.

The skimmer has some hairline cracks but the majority of water loss is coming from the spillway from the spa into the pool. Overtime water has eroded the grout below the spillway which is allowing water to escape behind the bricks.

I was losing anywhere from 1.5-3” every day. Since we located the source of the leak I have been able to reduce the amount of loss by running the pumps less and minimizing water flowing over the spillway.

I have been trying to get the original pool builder out to give me an estimate to repair it right but they seem to be giving me the run around.

Oh wow, you and I have totally different pool systems. I have a in-ground liner pool (no spa)

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Which Is why I and others have said the first course of action should involve ruling out evaporation as a factor and the best way to do that is “The bucket test”.

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How accurate is the bucket test?
I saw that there are a number of variations for the bucket test. I tried it by filling a 5 gallon bucket with water, had it next to the pool on the concrete. I found that the results were inconclusive.

Is there a particular bucket test method that you found is most effective?

I tried the bucket test (multiple times through a few different scenarios)...test indicates a leak.

I'm trying one more thing before I make a call to a leak detection company. I pulled the multiport handle from the sand filter, noticed a few "worn spots" on the spider gasket. I'll replace the gasket...cross my fingers (but I'm not holding my breath)...