All pools lose water to evaporation. However, if a pool has a leak, it may be losing water much more quickly. Not only does this increase the facilitys water consumption, but it can indicate a problem with the plumbing or structure of the pool. These issues should be fixed quickly so that the pool remains in good working condition. First, its important to determine if a leak exists and where it might be.
Mark the water level at the skimmer, using a piece of tape. Wait 24 hours. If the level has dropped more than a quarter inch, there is probably a leak somewhere in the pool. To be sure, use the bucket test. Fill a five-gallon bucket with water and place it on the pool steps, so that the rim is a few inches above the surface. Mark the water levels in the bucket and pool. Check the water levels after 24 hours. If the pools water level is lowered by more than the buckets water level, there is a leak.
The next step is to identify where the leak is located. Again, mark the water level of the pool. Turn off the filter and install winter plugs in all the lines. If water is lost, the leak is in the pool structure. If no water is lost, the leak is likely in the plumbing.
To find a leak in the plumbing, pressure test the lines and dig, until you find the line with the leak. A pool professional can find the leak without digging, using a geophone or more advanced sounding equipment.
To find a leak in the structure of a concrete pool, turn off the pump and wait at least one hour. Look for cracks along the surface of the pool structure. Squeeze food coloring near a crack. If the color is pulled into the crack, the pool is leaking at that spot. If there are no visible cracks, squeeze the food coloring near any items that are installed into the concrete structure: main drain, returns, lights, skimmers, etc.