A leak, somewhere, need ideas


In The Industry
Jun 2, 2007
Annandale, VA

The better part of last season I was troubleshooting my pool for a leak. Its a concrete inground, with equipment thats been upgraded in the last 5-10 years. I know its a leak because a) water has dropped a lot faster than in the past, I would say about 1" every 2-3 days, and b) I did the bucket test to confirm that water was evaporating faster from the pool.

Below are the things I've looked at (with my actions in parenthesis). This has been going on for a good part of last summer, and everything below has probably been checked a few times.

  • Above ground plumbing (looked around everywhere for small leaks, these would be obvious)
  • Components on pool pad like pumps, heater, etc... (did a visual)
  • Gap where pool meets plastic overflow body (pretty common for cracks and small leaks to happen here, I applied under water putty, but to be certain I should probably drain pool below the overflows and apply something better).
  • Light body (this is metal, but water could be seeping out where the electric wire comes into body, I applied a type of putty (black, flexible), but its' possible its still leaking)
  • Solar panels (did a visual on the roof)
  • Concrete/plaster (no cracks, pool was re-plastered a few years ago)
  • Underground pvc (this is what worries me the most. I have no idea how to find out if this is the problem. Only idea is to drain pool below outlets, and do an air pressure test. Would air seep out from a cracked underground pipe???)

That's what I have so far. I really appreciate anyones $.02 on this.



Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
That is a very small leak and is going to be hard to track down. 1/8"-1/4" per day is normal evaporation and you aren't much above that. 1/4" of water per day from your pool is about 80 gallons, so that would be a very obvious leak at your equipment pad or solar panels. But, the ground can easily soak up 80 gallons per day and you'll never notice it.

Seems like you've read this, but to just in case, Pool School - Leak Detection

The conduit in a light niche is designed to be flooded and should not be sealed up at the niche.

It is possible to pressurize plumbing, but I'm not sure on details of how.

One option is to let it leak until it stops and that will point to where the leak is. At the skimmer, returns, etc.


In The Industry
Jun 2, 2007
Annandale, VA
Hey thanks for the feedback pooldv! Just to clarify;
- I would say its' more than the 1/8-1/4 you mentioned, easily 1/2" a day. Either way, more than just evaporation. Having the pool for 13 years, I have a pretty good grasp on evap rates.
- For the light niche, I meant the back of it where the power cord comes in. There's a coupler, where the power wire enters the niche, with a little rubber compression thing that can fail. That happened to me because at one point when my pool water was really high (overflowing) after a big storm water was dribbling out of the grounding box. Grounding box sits @8' back from the deep end where the light niche is. You may know this, but that's where the ground is connected to a grounding rod. There's a plastic pvc pipe that leads from the niche to the ground box, which allowed the water to leak. At that time, the ground box was slightly lower the the overflow point of the pool. Either way, what it told me was that water was getting into that pipe. While I've raised the grounding box, its possible the pvc pipe is cracked somewhere.

I like your idea of just letting it leak until it finds its lowest point. That might help.