Pool leak mystery

[Lisa]

Our concrete pool is about 8 years old. I have never had a problem with it. Lately the water has been low. At first we thought it was evaporating and we would fill it up. But about 5 hours later, it had dropped about 4 inches. This only happens while the pool equipment is running. When we turn off the equipment, the water level does not drop. I am concerned that the leak is in the plumbing around the pool under the concrete deck. Does anyone have any suggestions?

[Smokey]

Have you let the level drop until the water loss stops or do you fill it up immediately? If you can find the level at which no more water is lost, you can often make a good guess as to where the problem lies.

With such a rapid water loss, you probably have a leak on the return line. A leak on the suction line causes air bubbles in the return jets which you never mentioned. I don't suppose there is any way to get to the return line pipes, is there?

[Lisa]

Thank you for responding. I did have some bubbles from the jets. I also have a fountain and the water stopped coming out of it. It just dribbles. The bubbles come and go. The other day I put my hand on the jet and nothing was coming out. No water, no bubbles, nothing.

[Smokey]

I would still guess at a leak on the pool return line. The pressure from the pump is causing the leak when it runs. Have you looked for telltale signs such as dampness, increased plant or lawn growth and vigor, etc around the swimming pool? Has the deck cracked or subsided anywhere?

If you're going to have to break the deck up, best to keep the damage to as isolated an area as possible.