There are some ways you can narrow down the reasons behind your leaky swimming pool. There are typically one of three swim pool issues with water loss.
Excessive Splash Out or Evaporation
If the pool is not being used frequently (then obviously), it is unlikely that the problem is splash out. On the other hand, if it is the middle of the summer, with high temperatures and lots of kids getting in and out (dripping wet) this could, in fact, be a real cause.
To eliminate evaporation or splash out pool water loss as a causes, here is a quick test that can be run on your swimming pool: Be sure to secure all pets BEFORE the test.
Place a 5 gallon bucket on the second step or bench seat and fill it with water so that it is exactly the same level as the swim pool. If evaporation is the cause of your loss, both levels should drop at the same rate If you have a pool leak, then the pool will drop faster than the water level in the bucket.
Leaks in Plumbing or the Pool Shell
Inspect around the filter pad for obvious leaks. Look for damp spots or drips. A steady drip can result in a lot of water loss over time. Does your pool leak more with the filtration system running vs. not running? If it does not seem to matter if the pool pump and filter system is on or off, then it is time to start doing checks in the pool: Start “plugging” holes – places like water returns, pool skimmers, and the pool main drains, one at a time. You might want to buy enough winterizing plugs for the returns and the auto cleaner. Try to plug up just the returns first and see if the leak rate slows down.You can screw a plug into the skimmers and see if you notice a water loss change.
If none of those seem to slow down the rate of water loss, you need to call in a leak specialist. These pool professionals specialize in finding and repairing leaking plumbing, etc. Contact your pool service professional.