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Hidden Water Line Leaks

Hidden leaks on a pressurized water line cause a lot of damage before you know they exist. The first clue is often a large water bill. They are usually underground, or under the foundation. This page is about finding them, then the options for fixing them.

Grandpa TJ tip

I’ve located videos which deal with many of the types of leaks you may run into at home. If you are handy with some simple tools and can get to a hardware store, these videos will give you enough information to get the job done for far less cost than a plumber.
- Grandpa TJ -

Copper repairs live on the visible-leak hub

The copper repairs (eight ways, temporary and permanent, and changing pipe type such as PEX) are on the Water Line Leaks draft, not repeated here. Check local building codes before any permanent repair on the house supply. If you are in doubt, talk to a plumber.

Plumber

How to find those leaks

Five parts of the old catalog, as cards. The how-to videos stay off this hub for now.

Finding leaks

Which pipes are yours, simple leaks to rule out before you hunt the big one, and how to tell a house leak from an underground leak or a slab leak.

Grandpa TJ’s cautionary tale

We found an under-slab hot-water leak because a section of floor was hot to step on, and the water meter confirmed it. There was no moisture around the hot spot, so mold and water damage were not factors. A company we thought was leak detection rushed out, skipped a moisture test, and set up fans to dry a leak that was not wet. If moisture had been on the slab or walls, fans would have been right. They were not, and they should have said so. I told them to pack up their equipment and leave. Do not get pressured into service you do not need. Ask a lot of questions.

Before you dig

Have local utilities mark underground services before you dig. It is often free, and in many places the phone number is 811. Do not turn a water leak into a power outage, a gas leak, or a broken internet or sewer line.

Underground leaks in the yard

Finding and fixing a leak in the yard: a plastic main between the meter and the house, a pinhole in a copper supply, a rusted PVC-to-copper union, and a well-pump-to-house leak found with an air compressor.

Slab leaks

What causes slab leaks, including what matters when you talk to insurance, what to know before you open a wall or floor, and pro repairs that expose the pipe or tunnel under the foundation.

The attic bypass

After a false start with another company, a leak-detection service mapped the pipe from the water heater to the bathroom. We bypassed the whole under-slab section through the attic and down into the bathroom, instead of jackhammering a 40-year-old pipe that was likely to leak again.

Bypassing slab leaks

Ways around a slab leak instead of opening the slab: overhead PEX, an exterior copper run, another PEX bypass, and a long copper bypass with the soldering work.

Leaks in walls or ceilings

Leaks behind drywall or in a ceiling. One had been running behind a toilet wall long enough to grow mold; a steel nail was touching the copper, not puncturing it. Another was a longer mystery leak.

Finding it still saves money

These leaks range from easy to difficult. Even if you do not do the repair, finding the leak before you hire someone is still worth it.

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