Although pools may be expected to lose water due to several factors, losing an inch or more per day is usually a telltale sign of a leak somewhere in the pool. The skimmer lines, which suction water from the pool to be filtered, cleaned, and returned, are a common culprit of such problems. Skimmer leaks can cause structural problems to your swimming pool and cost lots of money to repair, so determining whether a skimmer leak is to blame and then repairing the leak are of the utmost importance.
Find the Leak
If you believe your pool may be leaking, make a mark with a pencil at the side and monitor it closely over a few days. After several days, should your pool be several inches lower than when you started, it's time to suspect a leak. Skimmer leaks are usually indicated by the water stopping right at, or just below, the mouth of the skimmers inside of your pool. A dye test will help you to determine whether the skimmer is leaking, and where it is leaking.
Repair the Leak
There are a couple of different ways to repair skimmer leaks. The first, and more expensive, option is to have the skimmers replaced. Such an overhaul usually only happens when the entire pool is being renovated. It may cost over $1,000 for an average-sized in-ground pool. The second option is to apply some underwater putty or specialty material (one product, Fix A Leak, works quite well in pool skimmers) to seal the leak up. By following the factory instructions on these products, you will be able to fix your pool's leak quickly and easily. Should it continue leaking, the best course of action is to contact a professional for advice.
Preventing Future Leaks
Once the leak is fixed, you'll have a few things to think about. The use of chlorine may, over time, crimp the skimmer lines and cause leakages through breaks that form. Cracks in the plastic, or ill-fitting skimmer mouths, may also cause a leak in an in-ground pool. In the long term, you might want to consider contacting a pool leak specialist to determine whether these potential problems require an overhaul of your skimmer system, or if there are any measures you can take to prevent the problem from becoming worse over time.