Concerned I have a leak....


Well-known member
May 29, 2017
Worcester, MA
Hi folks:

I'm a second year pool owner having bought a house with a 40 year old gunite pool (32,000 gallons). Overall the pool is in good shape. It looks like it was refinished 5-10 years ago as there are chunks of plaster in the floor drain line (which is a different story.)

Anyway, I'm concerned I have a leak. Last year, during our first season as pool owners, I was shocked to see how much water the pool lost each day. But it seemed to be due to evaporation as it was about 1/4" per day which is "typical." We don't have a pool cover.

This year it seems to be losing a lot more. It seems I'm almost always putting the hose in every 2-3 days and filling it up an inch or so. We've been using the pool a lot and there has been a ton of splash out, so that could be contributing. But 3 weeks ago it was cool and windy and the pool was losing a bunch, and now its hot and humid and its about the same. The pool pump runs from 8 am to 8 pm. And it seems to lose just as much at night as it does during the day.

I'm going to try to do a bucket test starting this evening into tomorrow. I can use any type of bucket, correct?

I'm not sure why this is popping up now. Nothing really has changed vs last year other than I got an M500 robot. Could the robot have scrubbed off an old patch in the Gunite and it's now leaking? I see no evidence of cracks or patches.

One comment...if the pump runs constantly the filter housing and all lines are fully primed. No apparent air bubbles, etc. But if the pump shuts off at night, and back on in the AM there will be some air in the filter housing that I have to bleed off. Just a bit. But to me this seems like it shouldn't be. Air shouldn't be getting in. If it is..something is leaking.

Also...I've lost a lot of salt. I started at 3600 and am now down to 2800 due to what I assume are leaks. Evaporation would keep concentration the same.

Thoughts? How much water loss due to evaporation is "normal"? Where I have a concern is my floor drain line is partially plugged and I worry about water dropping below the skimmer.


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Hot, dry weather will increase evaporation, along with wind.

For reference, in the SW desert, I lose 3/4" to 1" of water per day due to evaporation.

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The salt loss is the tell. You are correct that with evaporation your salt level will not fall.

In fact, mine goes up over the summer due to salt in our fill water and MA additions.


In The Industry
Jul 8, 2010
Ashford, CT
In Eastern CT and the heat and evap has been very high the last week.

Concrete pools normally do not loose water through the shell unless there is significant crack or other structural damage.

Do the bucket test and yes any bucket will do, its not real scientific just a basic - yep there's and inch more in the bucket.

You can use a sharpie to mark the water inside and outside the bucket to make it easier to visually check.

If your loosing water I suspect a leaking pipe which would require a pressure test of your pipes..some guesswork or a pool leak specialist.

Again I would expect your pool shell to be at least 10 inches thick and if you were leaking in your shell I would expect the concrete to be soft or if you poked it with
a screwdriver it would be softer and crumble a bit.. you might also see rust stains where the rebar is rusting through to the top.. but I could be wrong on the shell, just have not seen it without a crack.. others?


Well-known member
May 29, 2017
Worcester, MA
Thanks all. I'll do the bucket test this evening.

I did locate a small leak on the equipment pad. It drips occasionally from the drain valve (think garden hose spigot) one drip every minute or so. And then it seems there is another slow leak around the backflush valve on my DE filter assembly. Again, not a spraying or trickle of a leak, but small drips that has left a wet spot on the pad about 1' in diameter.

Not sure that leak is big enough to cause what I'm seeing but will continue to check.