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Leak Detection and Repair

The majority of people who tell us their pool is leaking are actually not correct. So before you hire an expensive leak detection company, let’s see if we can determine whether there is actually is a leak, and where it likely is.

The Bucket Test

            To be on the safe side, you should perform a bucket test whenever you suspect a leak, plus every September so that you know you have no leaks before closing.  Marking your skimmer does not help unless you know exactly how much it rains and how much it evaporates. The bucket test does that for you.

Take a waterproof bucket.  Put some weight in it, like a couple of rocks or a brick. Put the bucket on the top step if you have steps, or hang it inside the pool from the top rail if you don’t. Fill the bucket enough so that the level inside the bucket and the water outside the bucket are at the same level.  If you use liquid solar cover, use pool water from the top of your pool for the bucket, so the liquid solar cover is in the bucket too.  Liquid solar cover prevents evaporation.

            Remove your real solar cover until the test is over.  Do not put the bucket on the deck – it doesn’t work. The bucket has to be in the water. Why? We need the rain and evaporation to be exactly the same in the pool as in the bucket.  The water will evaporate faster from the bucket if it is warmer than the pool water.

Now watch. Run the filter 48 hours straight and check it. If the pool and the bucket remain at the same level as each other, you don’t have a leak. If the pool goes down compared to the bucket, the amount it went down is the leak. If the bucket goes down compared to the pool, take the bucket off the deck, put it in the pool, and start over.

If you found a leak after 48 hours of filtration, measure how far down it went, then refill the bucket and repeat the test with the filter shut off for 48 hours.

If the leak is faster when the filter is running, the leak is in the filter, pressure pipes, or hoses. If it is the same both ways, the leak is in the surface.

If it leaks more with the filter off than on, it could be on the suction side, but retest to be sure. If the leak is in a suction line (skimmer or main drain), air leaks more than water; so that kind of leak would have made the pump shut off, lose its prime, or suck air. You would have noticed that problem way before you noticed a water leak. Solve the air leak, and the water leak goes away.

 Leaking Pipes or Hoses

First, look at your backwash valve if you have one. If it was leaking water when not backwashing, would you have noticed?  Is it connected to a backwash hose whose end is 50 feet away? Disconnect the hose right at the backwash valve, and look at the valve while the filter is running on Filter.  If it is leaking at all, that’s probably the problem. A little leak is a lot when it’s leaking 12-24 hours a day.

If not, look at your pump, tank, backwash valve, automatic chlorinator, heater, etc., on a dry day with the filter running. Look first at all the connections. Check all the clamps holding the hose or pipe or connections.  Perhaps add a second clamp with the screw facing the opposite direction of the first clamp.  Look under the pump, between the metal motor and the plastic pump. A worn pump seal can cause a leak.

Still can’t find it? For an above ground pool, every leak should have been out in the open. For an inground pool, you may want to do one more thing before calling a leak detection service. If it’s easy, dig up just where the underground pipe connects to the pool, and check that connection. Because pipes almost never break in the middle, they just get loose at the ends.

Surface Leak

It only takes a very small hole to leak a lot of water – like from a pencil or the back of an earring. So get in the pool and look. Every time you see a little dot, touch it, and see if it moves. You can hire a diver, and that’s what he or she will do.  But here’s the professional trick: first, they look under the ladder or steps because that’s where it almost always is – the part of the pool that gets moved by you.

Then, get Leak Detection Dye (we carry it), and put it carefully next to the skimmer, return, and other face plates; just in case they are loose and leaking. You’ll need to dive to the main drain to check that, because the inside of the skimmer and main drain would give you an air leak, but the edge of the faceplate would give you a water leak.

Old gunite/plaster could have cracks, and that means a new plaster job. Vinyl can have thousands of little holes that are almost impossible to see. Look outside the pool for the tree stump where the termites used to live before they moved under your pool for moisture – dry spells will make them do that. They like eating vinyl as much as wood. They probably drown when they chew through to the water, but then there are hundreds more right next to them to bite another hole.

And if you replace your liner because of ants or termites, see Agway or Blue Seal Feeds for the right treatment before you install the new liner. Put an impervious polyethylene sheet between the liner and whatever chemical they gave you to protect you and the liner from the chemicals.


Want to fix a hole in an underground pipe without digging it up? We carry No Leaks leak sealer. Just like a radiator sealant; it might work, it might not. And it can’t possibly be permanent. But $25 a year might be cheaper than $5,000 for a permanent fix! Or at least buy you time saving up for the big job.

Patching a vinyl liner is very easy, and permanent. We use a solvent that melts new vinyl to the original vinyl just as permanently as the original radio waves that melted the vinyl sheets to make your liner.  For success, follow these steps:

  1. Clean your liner well, and roughen it with sand paper if it’s smooth.
  2. Use the rough side of the patch or roughen it.
  3. Cut the patch with rounded corners because square corners will lift up.
  4. Make the patch about an inch bigger all around, than the hole or tear.
  5. Use American glue not Chinese. We only carry American glue. Most stores only carry Chinese glue –because it’s cheaper.
  6. You can patch under water, but follow the directions. If your patch is large, or very far underwater, fold it so that the glue is not exposed to water on the way down. Then open it when you are ready to put it on. Make sure that you squeeze out all air bubbles.
  7. Permanent patch kit glues are slippery, not sticky, so you have to hold the patch in place for about five minutes until it stays. If the water is very cold, that might be ten minutes. Best is to hold it tightly, so that the old vinyl and the new vinyl actually mix together to become one vinyl. Easy on the bottom – stand on it or put weight on it. Harder on the side, unless you are patient, and are good at breathing under water! Make sure the edges don’t curl up.
  8. If you can’t hold the good one in place until it sets, put a cheap a clear self-adhesive patch over your permanent patch. It will probably fall off in a year or two, but it won’t matter. It only needs to be there for five or ten minutes. And the self-adhesive patch doesn’t have to cover perfectly – just enough to keep the good patch in place.