7 Signs You Have an Underground Pool Leak

The hardest leaks to find are the ones you cannot see: the buried plumbing leaks that never break the surface. They are also among the most common. The good news is that even a hidden underground leak leaves clues if you know what to look for. Here are seven signs that your water loss is coming from below ground rather than the pool shell.

1. Damp patches in the garden

Water escaping from a buried pipe has to go somewhere, and it often surfaces as soggy soil or a permanently damp patch in the garden near the pool or the equipment. If one area of your lawn or beds stays wet when the rest is dry, that is a strong clue.

2. Unexplained lush or green grass

The flip side of damp patches: a leaking pool line is effectively irrigating the ground around it. A strip of unusually green, fast-growing grass tracking from the pool toward the equipment can mark the path of a leaking pipe.

3. Air bubbles from the return jets

When a suction-side line leaks, it pulls in air along with losing water. You will see a steady stream of small bubbles coming from the return jets, or air collecting in the pump strainer basket. This points firmly to a plumbing leak rather than the shell.

4. The leak changes with the pump

If your pool loses more water when the pump is running, the leak is likely on the pressure side of the plumbing, where the system is pushing water out through a crack. Water loss that depends on whether the pump is on is a classic underground-plumbing signature.

A leak that gets worse when the pump runs is almost always in the plumbing, not the shell.

5. Sinking or lifting paving

Water escaping underground washes away the soil and bedding that support your paving and pool surround. Over time, this shows up as paving that sinks, lifts or cracks near the pool. It is both a sign of a leak and a reason to fix it quickly.

6. Persistent air in the system

Beyond bubbles at the jets, you might notice the pump struggling to prime, or the water level in the pump basket dropping. Air being drawn into the system through a leaking suction line is a reliable indicator that the problem is underground.

7. A rising water bill with no surface explanation

If you are topping up the pool more and more often, and you have ruled out evaporation with the bucket test, but there are no visible cracks or wet spots inside the pool, the loss is very likely disappearing into the ground through the plumbing.

What to do about it

Underground leaks are exactly the kind that defeat guesswork, because there is nothing visible to fix. Locating them needs pressure testing and electronic listening to pinpoint the failing line without digging up the whole garden. If several of these signs sound familiar, a professional inspection will find the source precisely.

Frequently asked questions