Swimming Pool Leak (electronic question)

Why does the water not act as a traditional resistance (current increasing inversely proportional to distance between poles)?

Because you're dealing with a volume, not a length.

Why not just look for the wet spot?

Because he is probably an engineer.

"I have tried AC and DC. I Have tried to monitor current between the power supply and the probe. I have put both ground and power supply wires in the water, and monitored current between ground and the probe etc. All of these methods give pretty much the same results: the only significant current increase is within inches of the "leak"".

Is your liner supported solely by sand? If so, the general saturation by both seepage and surounding ground moisture will preclude a pinpoint locator using electrical flow. The supporting sand carries enough conductive moisture to mask a pinpoint leakage.

If all circulation in the pool is stopped and a suspension type dye were indroduced (a little imagination here) wouldn't it concentrate at the point where the seepage is occuring leaving an indicator stain at the leak point as the remainder fof the dye settles to the bottom?

From personal experience, I let our pool leak without adding water until it stopped dropping the teltale 1"/night. I then did a "walk around" inspection at the water/air interface to locate the small hole that was causing the leak.

C'mon everyone - jump in a let me know how dumb this sounds -- I dunno fer real.

This is probably an in ground pool with tile curbing and concrete side walks. I know the problem he is having. Ours was a 1 inch slit at the bottom. Easy to patch once you find it

You say the pool is leaking. How do you know this? What method did you apply to detect the leak? If it is simply a lowering of the water level, perhaps there is another explanation...

Chrisg288

Lowering the water level too low may be fatal with this vinyl liners. They are kept in place by the weight of the water.

Have you checked the piping? (usually solvent bond PVC)

If you can get between lining and ground pump air in. Bubbles should appear from the leak even if most of the air escapes through other crevices. I hope this helps. Good luck.

Interesting problem.

How many earth points are you using outside of the pool? I suspect just one.

If you treat this as a resistance problem, I would suggest that you need a grounding point at each corner of the pool (to start with!). The other pole to be exactly in the middle of the pool. measure current flow, you might be able to decide on which side the problem lies. Then place all the poles on that side in an arc, with the pool pole as the center of the circle.....measure further! Start digging (but with no water in the pool!!!)

Furthermore, if your leak is going downward, you may still not find it.....

Are you certain that evaporation is not the problem?

If it is a leak, see how far it goes down by not refilling........once its empty, you can check any bottom outlets better....

I wish you luck!

I have a non-electronic suggestion.

Try using hundreds or thousands of little lightweight balls (colored so as to be easy to spot. These should be heavy enough to sink but light enough to follow a current (not electrical current, water current).

Sprinkle these things into the pool and they will tend to congregate around the leak. What do you think?

I've just betrayed my electronics profession!

I don't have any experience in that but as far as i am concerned i would try to measure the Resistance ,maybe with a bridge, that should give you better answer-result and not the current .The difference is on the accuracy of the measure.

Drain the pool and allow the internal surface to dry then watch for a damp area where the water that has leaked out starts to trickle in the reverse direction. This will also give you an opportunity to closely examine the vinyl and do a bit of cleaning. You'll have to drain the pool anyway to patch the leak.

How big is this pool?

UH Dude... You do not have to drain the pool to patch a leak. You use a waterproof glue, smear it into the patch, then fold the patch in 1/2, glue side inward, dive down to the leak, peel open the patch, slap it on and you are done. I've done it a couple times. All you need is good healthy lungs. You only drain a vinyl pool as an absolute last resort, the vinyl has been stretched, and exposed to sunlight. It will in all probability crack and split when you try to re-fill it.

"the only significant current increase is within inches of the "leak"."

This sounds like you have located the leak. If so, then your question is about why the procedure or equipment didn't work better.

Am I right?

He meant within inches of the the simulated leak...

...that was his "pseudo-Leak", not the real one!!!

use a light powdery substance like zinc powder or talc in the water. It has to not be soluable in water. Mix this into the water and let it settle. The minute currents that are created by the leak will cause it to gather at the leaking spot. However this will only work if it is in the bottom of the pool. Die might work as suggested above but I think the concentration would have to be high and then you would still have to clean the pool after it was done. Unless you want to change your skin color.

I think your electrical solution is sound but I agree with some of the other posts that recommend more ground rods, however you should creat them in a loop not just one lead jumping from ground to ground. Doing this gives you multiple connection points to take your readings from.

I also thing DC would be the preferred voltage to use, I think i would use an AC transformer and run it through a voltage rectifier to get a better source for the current. Course a fence charge might just be the ticket.

Just a few rediculous thoughts but what the hey!!

Are you sure you have a leak? When I first had a pool installed, I thought I had a leak. But I found that on a hot day, it is possible to lose up to an inch of water due to evaporation. In the winter i covered the pool and water stayed constant level, proving the amount of possible evaporation.

I have patched many leaking pools and use a squeeze bottle with a trace of food colored water in it. I go down and with pumps off and water standing for a day, check the bottom for a little tell-tail of sand. It is usually located around the hole. If I don't find any sand I start at the lowest place and dribble a little colored water out and watch for movement. Follow the trail and I usually find the leak in just a few minutes. A patch of the same color vinal with water proof glue and the job is done. Oh yeah, I am a diver and do use a tank and don't stir up the water by splashing around. I would not suggest getting into the water if someone is charging the water with a fence charger.

If I'm looking for a short between power rails on a PCB I always drive a small current between the two rails then look for the point where the voltage gradient leads. DVMs are good at resolving very small differences in voltage.

Drive you're 25V into the centre of the pool (0V to ground) then use a long insulated "probe" (insulated wire stuck along the length of a broom handle) to look for the point in the pool where the voltage is lowest.

If it turns out that most of the resistance is between the leak and the ground terminal, you'll get better resolution by referencing the measurement to the positive terminal of the power supply.

The problem with looking for changes in current is similar to the reason that manufacturers of antistatic material quote resistance per square. In an infinite sheet of resistive matting the resistance between any two points is the same.

I hope this makes sense.

Try to call the contractor who installed the swimming pool, and if you feel that there is some defect you have to claim, do not waste your time & maybe you will lose the warranty by doing anything which can harm the swimming pool.

Good luck

Fadi

Many thanks to all who offered suggestions. I found the leak. My previous attempts involved having one side of a power supply grounded and using the other as a probe and measuring the current. This did not work.

The trick was to measure the voltage gradient in the water by using 2 spaced electrodes as a probe in the pool. with one side of the power supply grounded, and the other side as a fixed electrode in the water. This method worked great!

Using this method, the voltage gradient is near zero when far away from the leak. About 2 feet away from the leak, the voltage rises to about 50 mV, and increases steadily as you get closer. I get a max. of about 500 mV when on top of the leak.

With this setup, it took me about 10 minutes to find the leak. I was particularly impressed that I was able to find the leak in a place that I would never have suspected.

To reply to some of the suggestions:

Normal water currents (movement) are stronger than that produced by the leak, so physical methods (particles etc.) would not work. Dyes can be very useful, but you have to already know where to look. In my case, even when I knew where the leak was, dye did not work because I had to get in the pool, creating currents which dispersed the dye before it was sucked in.

Allowing the water to drain until it stopped leaking would not have worked, because the leak was on the bottom (and would have cost $$$$ to refill). As others have stated, draining a lined pool can destroy the lining.

Only one ground was needed. The method worked regardless of where the power supply electrode was placed.

Again, Thanks to all!

Tad

Tad,

Could you expand on "measure the voltage gradient in the water by using 2 spaced electrodes as a probe in the pool"?

I put two screws spaced about 6' apart inside a piece of PVC pipe. The srews were attached to a voltmeter. As you get close to a leak, the voltage goes up.

Tad

Hello Tad,

I'm still confused. I have a brother-in-law That has a leak and I would like to help him find it. (My wife and kids use his pool all the time, by invitation of course, and this would be a great payback).

I'll attach the power supply to ground and an electrode in the pool. Here is where I'm not sure, Does the meter connect one probe to ground and one to the two screws in the PVC pipe or does the meter connect one probe to each screw in the PVC pipe?

I appreciate your help in this matter.

Pepple

Pebbles,

The voltmeter is connected to the two screws. I tried measuring vs. ground, this did not work.

I used 40 VDC, negative to ground, positive to pool. The power supply has a current limiter, so it is fairly safe. This voltage could be dangerous, so I highly recommend some way of limiting the current! A nine volt battery would probably work, and be safe.

My technique will not work with vinyl lined pools, not concrete. All potential grounds should be removed from the pool if possible, as they will look like leaks. Any metal (such as ladders) going into the pool may be grounded. In-pool lights are grounded. The center drain in the bottom will give a high reading.

If you use a metal pole, be sure that you use gloves or wear rubber shoes, so that the rod is not grounded through your body. Concrete is fairly conductive.

The technique will only find leaks in the actual liner. If you Google "swimming pool leak", you will find many good guides to finding leaks. I highly recommend checking all fixtures first using the dye test, as well as the other recommendations.

If the water goes down to a certain level then stops, the leak will be at the water line. Skimmers are notorious for forming hairline cracks.

Good luck!

Tad

I tried this method. My power supply is only capable of 30 volts. I was able to drive a current of about 50 mA.

I started measuring the voltage drop at various points in the pool and found a drop of about 2.5 volts at both sides of the skimmer on the inside of the frame about 1 inch bellow the waterline. I then put a die to see if it gets sucked into the leak there but nothing happened at least I could not see the die being sucked.

I am wondering if it is normal to have such a drop at the skimmer frame.

Is the fact that I can drive a current of 50 mA evidence that there is a leak?

Claude

Claude,

Anything that is grounded will "look" like a leak. The central drain at the bottom is almost certainly grounded, so will give a reading. In my pool, one skimmer gave a high reading, and one did not.

Other objects that will be grounded include metal ladders, underwater lights, rings underwater to attach a safety buoy rope to indicate a shallow end etc. Any metallic fixtures in the water are potentially grounded. Because of these sources, drawing a 50 ma current does not necessarily mean you have a leak.

A way to see if your setup is working is to put a grounded wire into the pool, to act as a simulated leak. As you approach this wire with your probe, you should start to get a pretty good voltage gradient starting a couple feet away, which will steadily increase as you get closer. This will give you a feel how the device will react as you get close to a real leak.

Also, the technique only works well in open water. Inside the skimmer. the electric field lines are partially blocked, and will give low readings.

Good luck!

Tad

Thanks Tad. I will try the ground wire trick to see if the setup works.

Claude....

Best suggestion I can give you let it leak down until it stops check the liner at the water level. That will reduce the amount of surface you have to inspect.

What about water pressure? The deeper you go the higher the pressure. Is it possible to have a leak on the bottom and as the water level drops (reducing the pressure at the bottom) is it still possible that the leak is on the bottom and not at the water line?

BTW...thanks for the expanded info TAD.

If anyone has a PVC, or black poly leak, it can now be fixed without excavation!! Pipes Down Under can now install a "pipe liner" the entire length of the pipe! Email me at dwgearup@aol.com with questions.