leak somewhere - how do the Pros find underground leaks?

CountryBumkin

Bronze Supporter
Jan 9, 2017
124
Orlando/FL
My pool water is dropping. It's not evaporation and there are no external visible leaks.

How do the professional leak detectors find underground leaks (sonic detectors, etc.)?
 

rmasonjr

Well-known member
Jan 31, 2014
45
Brookhaven, MS
Not a professional, but I did the syringe with red food coloring test at my main drain. I had to use a dive belt to hold me down and squirted the food coloring around the different parts.
Luckily, it wasnt my drain, rather a dime-sized hole in the vinyl. Repair was easy and new liner the following year.
 

ship of fools

Well-known member
Nov 9, 2011
546
Albany, NY
My pool water is dropping. It's not evaporation and there are no external visible leaks.

How do the professional leak detectors find underground leaks (sonic detectors, etc.)?
They put a small electric charge in the pool with a battery and then connect a ground rod outside the pool. That charge will seek ground which will be through a hole in your liner. They have directional listening devices to help them locate the hole(s) and then they remove the charge and dive in and fix it.
 

pooldv

Mod Squad
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Aug 10, 2012
25,148
FL panhandle
They put a small electric charge in the pool with a battery and then connect a ground rod outside the pool. That charge will seek ground which will be through a hole in your liner. They have directional listening devices to help them locate the hole(s) and then they remove the charge and dive in and fix it.
That is used for vinyl liner pools.
 

CountryBumkin

Bronze Supporter
Jan 9, 2017
124
Orlando/FL
Researching this, and from this forum, the two most common places for my gunite pool to leak are the skimmer and pool lights.
Just wondering how to figure this out without paying someone. The leak is small and slow (wherever it is) but I have noticed the pool water level drop at least 2 inches since I turned off my automatic pool filler a couple of weeks ago. The water level in the raised spa has not dropped so I can rule out evaporation.

If the leak is at the pool light, and I pull the light out to replace the "cable seal", the conduit is going to fill with water as soon as I pull the seal out (if it's not already full) so I lose the opportunity to determine if this is the spot where its leaking. But maybe this is still best do-it-yourself method - then I can just wait and see if the water level stops dropping.

If the leak is at the skimmer-to-pool shell connection, it is suggested to let the pool water level drop to below the skimmer and see if it stops leaking further. That's a good test but it also means I can't run the pump/filter for a while (maybe weeks) until the level drops below skimmer. So if there is another faster way to figure this out, I would like to know.

Lastly, it could be leaking at the returns or underground piping. But if I deal with the pool lights and skimmer possibilities myself, at least I'll narrow down the possibilities.

I guess I'll start by replacing the pool light seals (and if you remember me from my other posts, I have an issue with the SAM light not working too, so maybe I just replace it now while I'm there). Don't you just love pool ownership?! :D
 

CountyBumkin

Bronze Supporter
Apr 3, 2016
57
Orlando FL
Yes I saw that link. But the info in it is not very specific - which is why I posted.

Plugging the returns is possible if I can find/buy plugs. Or maybe I just let the pool level keep dropping and see if the drop stops just past the level of returns. I won't be able to block main drains but there are plenty of things I can test and rule out before I need to worry about mains.
The frustrating thing (or maybe I should think of it as the "good thing") is the leak is very slow. It's been about two weeks now and the level is down like 2 inches.
 

duraleigh

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Apr 1, 2007
31,503
Sebring, Florida
It's been about two weeks now and the level is down like 2 inches.
Hmmm. We typically think of a leak being in excess of 1/4" daily. Why do you know it is not evaporation?
 

setsailsoon

LifeTime Supporter
TFP Guide
Oct 25, 2015
916
Stuart/FL
Country,

First confirm you definitely have a leak using the bucket test. The reason I say this is I see you're in Orlando just a couple of hours north of us. We had a couple of weeks where the wind was much stronger than normal and low humidity. Normally we don't add water to our pool more than once or twice per year but we were adding every 10 days for a while. I thought I had a leak too and ran the bucket test to confirm it was only evaporation. Now that the wind and humidity are back to normal I don't add any water. Wind velocity is a large factor in evaporation rate. Here's a link to the test.

I hope this helps.

Chris
 

CountryBumkin

Bronze Supporter
Jan 9, 2017
124
Orlando/FL
I have a raised spa (with spillover into the pool). The water line in the pool and spa line up with the upper most horizontal tile grout line when both are full. The Spa water line is still at the grout line, but the pool water line has dropped 2 inches below the grout line. If the water loss was due to evaporation wouldn't the spa water line also be 2 inches below the grout line? Is my reasoning correct?

@setsailsoon, I guess I should run the bucket test - it doesn't cost anything to do the test.

My pool is normally connected to an automatic pool filler so I would not notice a small leak (the downside to these auto-fillers) - but now that I have turned off the water to the automatic filler to replace the flexible hose from the house bib to the filler line, I notice the water level is low. Maybe the spa water level just doesn't evaporate at the same rate (less surface area). I don't know.
 

pooldv

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Aug 10, 2012
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FL panhandle
No, if your spa spillover runs daily it will stay full and the pool level will drop. 1/8"-1/4" loss per day is normal evaporation loss. More when it is windy or low humidity.
 

setsailsoon

LifeTime Supporter
TFP Guide
Oct 25, 2015
916
Stuart/FL
I have a raised spa (with spillover into the pool). The water line in the pool and spa line up with the upper most horizontal tile grout line when both are full. The Spa water line is still at the grout line, but the pool water line has dropped 2 inches below the grout line. If the water loss was due to evaporation wouldn't the spa water line also be 2 inches below the grout line? Is my reasoning correct?

@setsailsoon, I guess I should run the bucket test - it doesn't cost anything to do the test.

My pool is normally connected to an automatic pool filler so I would not notice a small leak (the downside to these auto-fillers) - but now that I have turned off the water to the automatic filler to replace the flexible hose from the house bib to the filler line, I notice the water level is low. Maybe the spa water level just doesn't evaporate at the same rate (less surface area). I don't know.
Country,

As pooldv says the spa is filled up every day when the spill over is operating. You should run the bucket test. A rule of thumb for trouble shooting a boat problm that works well for pools is "Always check the simple stuff first". Nothing is easier than the bucket test.

I hope this helps.

Chris
 

kadavis

TFP Guide
In The Industry
Apr 5, 2015
1,463
tucson, arizona
In your other post you were having trouble getting a light out, is it possible you have damaged the conduit and this is where it's leaking. You mentioned pool light seals are you talking about cord stoppers that keeps water out of conduit.
 

JonG

New member
May 8, 2013
1
Southern California
CountryBumkin,

Several years back we were losing more than an inch a week and failed the bucket test, so I called a service. Within a minute of entering the backyard, the tech said he had a good idea of the cause, but he would perform several checks to verify. His theory was that the benches in the spillover spa were formed from "rebound", which is waste from the gunite process and therefore unstable and flexy. Heat/cool cycles in the spa were said to exacerbate it. He did the typical tests like dye near the skimmer, and plugs, but he was proven right about the spa. When the water level went below the benches there was a a big wet crack, not otherwise visible, in the top of a bench. It was hard to believe it could leak that much water.

I'm pretty handy but there's no way I would have figured that out. The remedy was to jackhammer the spa interior out and rebuild it. It was a noisy process and not cheap, but the leak stopped.

Good luck!

Jon
 
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