Leak detection - suggestions?

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G

George in Georgia

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Jul 9, 2010
69
Jonesboro, GA
I've been struggling with water quality problems, and running the filter 24/7 for a couple weeks. Friday I noted more of a drop in level than would be just evaporation, so I marked the pool level and set out a measuring cup filled to the one cup level. Saturday morning the pool was down by 3 inches, and below the skimmer inlet.

Since the liner is old - it has two tears above the water line, I suspected a liner leak. Since the water was cloudy, I added some flocculant from Leslie's Saturday afternoon. It calls for 2 hours of recirculation, then no filtration for 1 or 2 days. I also marked the water level when I shut off the pump.

This morning there was no perceptible drop in water level.

I suspect a leak in the pressure side. Does anyone have any experience in dealing with this? I hesitate to replace the liner before this newest problem is fixed.

The pool is inground, about 25K gallons.
Sand filter, 1 hp pump.

Thanks for any advice.
 
Welcome to TFP.

I assume that you don't see any water anywhere. Is your waste line plumbed away from the filter with opaque pipe? It's not uncommon for the multiport or slide to leak water into waste line while the pump is running.
 
Any progress? I'd try all the simple stuff (i.e. losing water out the waste line = spider gasket problem) before getting too worried about underground leaks. Based on posts on this site, the vast majority (>90%) of leaks are above ground.
 
Don't rule out evaporation without doing full bucket test.

Just today at night time, i happened to walk outside next to the pool with a flash light. I actually saw fumes coming from the pool. At first i thought that it is some dust, but then when i shined the light low toward the pool length, it looked like the pool is boiling....
The water temperature is about 95F....after crazy hot week here in so cal. At night now it is about 62F
 
Many thanks for the suggestions. I've been away since last Tuesday on a family matter, so the pool has just sat, no pumping. Water loss seems more than the evaporation from a measuring cup left out. Sunday afternoon I ran the pump sourced from the main drain (water level is below the skimmer) for two hours and saw no dectable drop in water level. This is encouraging!! It suggests that the returns are okay.

Today I'm adding water to enable using the skimmer; I'll try the two hour test again. Since the liner is in rotten shape I'd be "happy" to find that a replacement would solve the problem.
 
An update. Since my last post I've run the pump/filter from the skimmer and from the main drain for 12 hours or more with NO discernably different drop from the bucket test. Loss since my last post is about 1/4 inch, easily accounted for by evaporation. The dogs seem to have drunk from the test bucket; it shows about an inch drop.

Talking to a dealer about a new liner he mentioned that a bit of trash could stop up a liner leak. Sounds reasonable. That could explain the sudden 3 - 4 inch drop, and its "miraculous" cure.

Melt in the Sun mentioned that plumbing leaks accounted for only about 10% of all leaks. Since my plumbing seems to be all underneath concrete, with no indications of the slabs sinking, perhaps my situation falls into the 90% of leaks, the liner.

Any thoughts from The Collective Pool Brain???
 

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Just to clarify what I meant; >90% of plumbing leaks are above ground; I wasn't including liner leaks. These are even more common, and can be even screwier to locate. You said a bit of trash could stop the leak; is your pool swampy right now?
 
Ah, 90% above ground. My above ground plumbing is within a pool house and goes directly into the building's concrete slab. Pool is swampy now, I see no reason to adjust the water when it will be pumped out.

I ran the filter about 18 hours yesterday. No drop in water level other than evaporation via the bucket test.
 
OK, have you done a test, pump off, with the water level above the skimmer opening? That would lose water if it is in your suction pipes and below the pool water level.

If you can't get a consistent leak rate with the same set of circumstances, I would lean toward one of those squirrelly liner leaks, and just have it replaced.
 
Sorry for the long delay in a response. In the mean time we've gotten two bids on replacement, both from established local companies. After careful comparisons we chose a company with 13 years' experience. Discounting the set-up chemicals to be furnished by the somewhat higher bid, the difference was about $200, plus the lower bid was for a 30 mil liner, vs 20 mil for the slightly higher. BTW, the pool was installed in 1993 and to our knowledge it had its original liner. I'd say we were overdue!

Installation was finished in about 1 1/2 days and went smoothly. The pool is now in use, and is beautiful - crystal clear. We're using up some CaHClO shock while we add NaCl for the SWG, plus NaHCO3 for pH. All that alphabet soup! The CYA is at about 30 ppm after 4 days, can't rush that.

A couple of questions:

The info that came with the liner wants total alkalinity at about 100 ppm, and calcium hardness at 100 ppm minimum. I seem to recall reading either on this site or another similar one that calcium is unnecessary for a vinyl pool. Any comments?

The main drain was cleared of debris when the VGBaker drain cover was installed. Nevertheless flow though it is minimal; if the skimmer is turned off I risk cavitation in the pump. There is an auxilary intake plumbed with the main drain at the same level as the return nozzles, it is presently plugged off with a threaded gasketed plug. Could this be used as a point to pressurize the main drain by shutting off the drain circuit at the pump and then using compressed air at say 25 psi to perhaps dislodge plugging materials? Or should I just leave well enough alone and enjoy my rejuvenated pool.

Many thanks for members' advice and sympathy. At least here near Atlanta we have considerable swim time left; my wife, a native of Florida, says we'll break the ice to take a dip! We'll see about that!
 
The liner doesn't need calcium; however, if your warranty requires it you'll want to comply. 100 ppm is really low; your tap water may be higher than that.

As for the drain, not sure what the wall fitting would be. To see if there's a clog in the drain, the easiest thing would be to open up the pump basket, set the valve to main drain, and use a drain king (self-sealing hose attachment) to use water to pressurize the pipe with hose water. You may be able to use air as you suggested, but that seems like an unlikely way for it to be plumbed.
 
The folks who installed the liner think that the wall suction fitting may be intended for a Kreepy-Krawly or such, and thus not plumbed to the main drain. But, with a gasketed plug installed in it there is some flow through the main drain. When I dumped a couple bags of salt onto the main drain, in only 30 or seconds I could "see" the return flow; the dissolved salt raised the density of the return water so that I could see the difference between it and the surrounding water.

So, I wonder if I could "blow" out the main drain by pressurizing this secondary suction port, either with the drain king Melt in the Sun suggested, or with an air compressor, limited to 25 lbs or so.

Or, maybe suck it out by connecting the pool vacuum hose to the port. Any thoughts out there?
 
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