My Winterized Pool is Leaking Water!


A frantic pool owner called in earlier this week. “I just looked under my pool cover, and the pool water level is down to the floor! Help?!?”

The call was routed to my desk, and I began a process of elimination, which is winter leak detection, by asking a series of questions:

  1. What type of pool – gunite, vinyl or fiberglass?
  2. What type of cover – water bag, or safety cover?
  3. Was the pool losing water during the season?
  4. Have you ever lost this much water before?
  5. Is the water below the returns and pool lights?


The first question is very important, in that gunite pools rarely leak from the shell, with the exception of around pool skimmers. Vinyl liners can leak from anywhere, from small holes, or wherever the vinyl has been cut, for stairs, returns, pool lights. Both types can leak water through the main drain, but this is not a common area for water loss, except on very old pools, or large pools that use a spring loaded hydrostatic relief valve.

bulge-in-liner from water underneathAll pool types must keep water in the pool – all the time. It protects the surface and keeps the pool from ‘floating’ if enough hydrostatic pressure is beneath the pool. Vinyl pools can float too, when enough water gets underneath the liner.

Liners that leak past the shallow end floor may end up with wrinkles or a damaged pool liner, when refilling the pool. Gunite and Fiberglass pools can actually pop out of the ground, if enough water weight drains out!


The second question is also important, because if you have a safety cover, like we have in the picture above, at least the cover won’t fall in the pool when the water drops this much. However, if a heavy snow load falls on an unsupported safety cover, it will damage the springs and possibly break some straps.

pool-cover-fell-into-poolSolid pool covers with water bags will fall in the pool, slowly slipping in as the water level of the pool drops. This makes it easier to see that there is a problem with the water level, but if something is not done quickly, you risk contaminating the pool if a messy solid cover falls in the pool.

Keep the water level in the pool no lower than about 15 inches from the top of the pool coping. Not enough water in the pool, and solid covers fall in the pool, and safety covers are at risk for damage.

pool cover-pump-on-a frisbeeIf you have a solid pool cover and use a pool cover pump, I’ll have to ask… “is it possible you have been pumping out pool water, through small holes in the pool cover?”. This is more common than you think. To avoid this, place your cover pump on an upside down Frisbee┬« and position it far away from any known or suspected holes in the pool cover.


Questions 3 and 4 are important to the investigation, establishing any pre-existing conditions or trouble with pool leaks. Often, pool owners aren’t aware that they are losing water during the season, if it’s slow enough and there’s a lot of rain. I’ll usually ask them how much water they add during a typical summer week. If it’s more than 1 or 2 inches – they may have had this leak for some time.


The point at which the water stabilizes is a good area to look for a leak. Be aware that recent rains, or water on top of a solid cover will raise the water level in the pool, so the leak may be below the current water level.

Water level stains (bathtub ring), or debris found stuck to pool surfaces, may indicate the level or location of the leak. Looking closely around the stabilized level will usually help you pinpoint the leak, checking the pool surface and any exits of the pool, including the returns and pool light.

For more information on pool leak detection, see a related blog post I wrote “Find and Fix Pool Leaks“.

WAIT UNTIL SPRING?filling-the-pool

In most winter pool leaks, the option to drop a hose in the pool and fill it up as needed certainly exists, and may be a better solution than fixing a leak during winter. If you can however, take a look to see if you can’t find and fix it now.

If the pool cover has already fallen in the pool, pull the cover out, clean the pool, and try to find the leak. If you still can’t locate the leak, fill the pool (after cleaning), balance the chemistry, and put the cover back on the pool.

frantic pool ownerReturning to our frantic pool owner who called in for help on his leak – it turned out to be a false alarm. During our time on the phone, the customer mentioned that a month ago, he had to siphon some of the water, because it was too high, “…and now it’s too low!” he told me.

Digging deeper into his siphoning methods, we figured out that he doesn’t have a leak after all – he just over-siphoned the pool!

“Add 10,000 gallons, and call me in the morning” I told him. ­čÖé

Davy Merino
InTheSwim Blog Editor



My Winterized Pool is Leaking Water! — 10 Comments

  1. I have an above ground pool that leaked last year for the first time just be low the skimmer. So before I opened it last summer I change the gasket behind the skimmer. I thought this would fix the problem but again the pole level is lower. Should I check for leaks in the liner or change the whole plastic skimmer box completely? Thank you for any advice

    • Hi Sean, I assume that your pool is just now being opened. If your pool cover had any small holes in it, your cover pump could have lowered your pool water level, by pumping water thru the holes in hte cover… but assuming not, then I would first inspect closely around the level of the water, before filling, looking for any holes in the vinyl, or any debris stuck in a hole, which gets sucked in there by the water. You can then use food coloring to dye test (might need to add an inch of water first). You can also dye test the skimmer faceplate, and also the return and light rings, if applicable. No need to change the hole skimmer, unless parts are cracked or missing. Skimmer faceplates, by the way – must be tightened Very Tight! Use a large #3 Phillips head to really crank the screws down until you hear the plastic creak. Also, two gaskets should be used, one behind the liner against the wall, and one on top of the liner, underneath the faceplate.

  2. Hi, I have a semi-inground pool with salt-water system. I woke up yesterday to find the pool cover lying in the almost completely empty pool. I think the pool cover siphon drained it overnight when the cover straps tore. My son climbed in to remove the large blocks of ice from the cover and we siphoned off the rest of the water. I added water (almost at the half way mark now) and was able to repair the cover straps. Can I add shock and ph without attaching the pump? I’m not able to take it out of storage without my husband’s help.

    • Hi; yes you can add chemicals without the pump running. Dissolve your ph chemical in a bucket of water, and pour around the edge. Rinse the bucket clean, fill with water again, and then add granular chlorine and dissolve it by stirring for 1 minute. Pour the solution into the pool, being careful not to let undissolved granules fall in as the bucket empties. After adding chemicals, use your pool brush to distribute by creating some circulation with the brush.

  3. We have an inground pool. the saftey cover has dropped into the pool at one section. We cannot get out the pool due to snow levels around the pool to look under it (and I am not sure how we would be able to see anyway). Mid summer we had a leak crew come out and the plugged all the leaks in the pool and the water level remain stable for 2 months till we closed. Now this. There is nothing we can do now till May when we open correct?

    • Hi Beth, Safety covers are not usually affected by water level in the pool, unless the water level drops lower than 18″ from the cover – in such cases, the water level no longer supports the cover, and when wet/heavy snow and ice falls, the weight can bend cover springs, or tear cover straps. In your case, if the water level has dropped to a very low point, you can add water to the pool from a hose, to raise the water level again. If you can remove some of the snow, you can look under the cover, or cup your hands around your face and put your nose right up to the cover and you can see thru a mesh cover, to check water level. It could be possible that the water level is normal, and what you are seeing is the cover stuck to the ice and being pulled/stretched down. Let me know if you have other questions. When the ice thaws enough, pull the cover back tightly over the pool, and if there has been water loss, add water to fill. If it drains again, remove the cover and look around the water line (where the water level stabilizes) for failed patches, obvious holes, or places where you see debris stuck to the liner (stuck in a hole).

  4. I came home yesterday to find our solid inground pool cover had fallen in the pool but more importantly, the water has leaked out SOMEWHERE down to about a few feet in the deep end. We have a vinyl cover that we planned to replace in 2018 but which we thought still had some life in it. My major concern is whether the ground around the pool is safe. Is there a chance for a sink hole or anything since all the water has clearly seeped into the ground? Also, what could have caused this so suddenly and dramatically.

    • Hi; likely no problem with the ground water, no worries there. Two things could have caused this, maybe 3. first is a wild animal that fell in the pool, trashed the cover and ripped the pool liner trying to get out (he may still be in the pool(!). #2 – old liners can sometimes just ‘snap’, because they become so brittle, that they just rip, during one cold day. #3, a pool cover pump, used for solid inground pool covers, could have been placed in an area of the pool cover which had a hole – and then the pump began pumping out pool water, through the hole in the cover, until the pool was so low, that the cover fell in the pool.

  5. Hi, I have an above ground pool, one of the rods popped through the liner making a perfect round role, little like a half dollar, is this fixable, another issue we had a gopher go under the liner about two years ago, should we try to work our his tunnel damage or can that hurt the liner, pool only 4 years old..

    • Hi Kathy, the small hole sounds patchable, with a regular vinyl patch kit. Doing it on both sides of the hole will make it stronger, to prevent further rupture (hopefully!). You can also wrap the rod end with duct tape or something to pad it a little, or cover the sharp edge of the rod. For the gopher tunnels, I assume that you have a sand floor under the vinyl. You can smooth out the edges of the tunnel using a rounded blunt instrument. I like to use a 3-4 ft length of PVC pipe, attached to a 2″ Tee fitting, and use it as a ‘sand hammer’, while standing in the pool and wearing a swim mask, to reduce the edges of sand divots (or gopher tunnels!).

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