Believe it or not - it is much more important to find a leak and take care of it before closing your pool up for the season than having a leak during swimming season. While you're using your pool, if you are losing water you can refill it and keep the pool up and running even though you are having the added expense of the water your putting in on a regular basis. Once the pool is covered, the leak becomes a much bigger issue if not fixed.
If you have a cover with water tubes holding it down and your pool water slowly leaks beneath the cover, the best scenario is the cover falls into the pool. If there is a layer of ice at the the water line and the pool is leaking, this creates a space between the layer of ice and the surface of the water. The rain water or snow weight on top of the cover can cause the layer of ice to fall, and sharp edges can shred the liner around the walls of the pool.
If you have a safety cover that anchors into the deck, the cover needs the water level to be at the correct level as the safety cover depends on the water underneath to help support the cover. If the water drops lower than 18" from the cover, and you have a snow load on the top of the cover it will either rip the straps, bust the springs or even pull the anchors right out of the concrete deck.
Is Your Pool Leaking?
Sometimes it is very easy to see if you have a winter leak. If you have a mesh safety cover, your water level should be rising under the cover from rain water. If the water level is falling, you have a leak. On a water bag cover, if you have a lot of water weight on the cover, it will dip down, but only to a point if there's water underneath to support it.
It's important to check your pool water level during the winter, especially if you thought you had a leak during the summer. There is very little evaporation during winter, if any at all. With mesh covers, if you kneel down next to the pool, and place your hands around your eyes, you can see through a mesh cover during daylight. Or, you can pull off a corner and take a look. For a solid pool cover, if the cover seems to be falling into the pool, dipping down more than it did, you may have a leak. Pump off any water and remove any debris before checking the water level, because weight on top of the cover will press down on the pool water and cause it to rise higher up the wall.
Winterizing a Leaking Pool?
I can’t stress enough to not close your pool and cover it, if you suspect a leak. If you do not want to take care of the leak before closing the pool, close it the way you normally do but you may be better off not covering the pool. Add water during the winter to keep it at least a foot above the shallow floor. This way, you can monitor it, and won't create more problems or ruin your cover. You will have more of a spring clean up, but can avoid some larger issues.
I had one customer with a mesh safety cover on a large Grecian pool who was losing water after the pool was closed the snow kept pushing the cover lower and lower into the pool. They didn’t think anything of it and came home from work one day and one of the brass anchors had pulled right out of the pool deck and actually shot right through a window shattering the glass and ended up on their living room floor. There was hardly any water left in the pool and the cover could not support the snow load weight.
There was another customer where their water bag cover fell into the pool and when we opened the pool in the spring the water level was right at half way up the pool light. We found out the electrical PVC conduit behind the light had come apart. If this had been taken care of before closing the pool it would have saved a lot of time, effort and expense during pool opening.
Holes in the Pool Cover?
Having a hole in any type of winter cover can make more of a clean up when you open the pool, as it can let dirty water and debris enter the pool. Holes in a pool cover are more of a problem with a water bag type cover. On a solid cover with a cover pump, if you place the cover pump near the hole, you can end up pumping out pool water, through the hole. which makes it seem like your pool is leaking. To avoid this, place your cover pump far away from any holes in the pool cover.
Another trick is to place your cover pump onto an upside-down Frisbee. This usually prevents both pumping water through the holes and helps prevent more holes from a sharp edged cover pump. Also, if you do have holes in a solid pool cover, tighten up the cover as much as possible, pulling it up out of the water, and placing extra water bags or weights around the edge.
If your cover is oversized, and you have some material folded under, sometimes you can slide the pool cover, so that the cover hole is close to the pool edge, or even over the pool deck, where it won't be a problem.
Finding Leaks in a Winterized Pool?
STEP ONE: Remove the pool cover completely. Fold it up onto one side or end of the pool, where it can sit for several days or a week.
STEP TWO: Mark the water level with a marker, or a piece of tape, so you can know if it is still leaking, or if it has stabilized.
STEP THREE: When the water seems to stabilize for a day, inspect the pool walls closely at that point. It's common to see debris sucked into a hole, where the water is leaking out, so look for this. Dye can be used on anything under the water level that looks like a hole. If the water level stabilizes at the pool light, consider that the cord conduit may be leaking. You can use a cord stopper to seal up the conduit.
Other common areas for leaking on a vinyl pool (besides the liner) are any other areas where the liner has been purposely cut and gasketed. This includes the pool light, and also the skimmer, returns and all 3 sides of steps and seats. If your water level has dropped below these, and continues to leak, you can look in other areas - but always consider that there may be more than one leak.
Should I Add Water?
If the leaking continues toward the shallow end pool floor, you should add some water. Always keep at least 6 inches of water covering the shallow end floor, or else the liner will relax, and pull away from the walls. With cold weather it will shrink, and it may not go back into place - leaving you with wrinkles or worse, it can rip when the pool is filled again.
So, yes - add water if you do not want to mess with the leak now, or if you are having trouble finding the leak, and are ready to give up - for now.
As I said in the beginning, a winter pool leak can be more of a problem than a summer pool leak. Let us know if we can help you with any winter pool leaks on your pool. We've chased down a lot of leaks over the years.
SPP Pool Expert