Signs of a slab leak in a Las Vegas home

Valley homes sit on concrete slabs, which means water supply lines commonly run underneath the foundation. When one of those fails, the leak has nowhere visible to go, so it runs for months while eroding the soil under your house.

The good news is that slab leaks announce themselves, just quietly. Here is what to listen and look for.

The clearest signs

• A warm or hot patch on the floor. This is the most specific sign there is, and it means a hot water line is leaking under the slab.
• The sound of running water when every fixture in the house is off. Stand still in a quiet house and listen.
• A water bill that jumped with no change in how you use water.
• Flooring that has started to lift, crack, buckle or discolour in one area.
• Damp carpet edges or baseboards with no source above them.
• A musty smell, or mould appearing low on a wall.
• Hot water pressure that dropped while cold stayed normal.
• New cracks in drywall or around door frames, which can indicate the slab beginning to move.

Confirm it with the meter

Before calling anyone, this takes two minutes and tells you whether water is escaping at all.

• The water authority test for a hidden leak is simple: shut every fixture off and watch the flow indicator on the meter. If it still moves, water is going somewhere it should not. (Southern Nevada Water Authority)
• The EPA reports that about 10 percent of homes have leaks wasting 90 gallons a day or more. (US EPA WaterSense)

Why it matters structurally

A slab leak is not only a water bill problem.

• Valley homes sit on slabs rather than basements in large part because of caliche, a hard calcium carbonate layer in the desert soil. It is also why a leak under the slab is a specialist job rather than a quick dig. (US Geological Survey)

What happens next

The sequence is detection, then a decision. Detection uses acoustic listening equipment, thermal imaging and pressure isolation to locate the leak precisely, so only that spot gets opened rather than a room.

Then the choice is a spot repair through the slab, a reroute that abandons the under-slab line and runs new pipe overhead, or a full repipe. The first slab leak in a sound system is usually a spot repair. By the second or third you are paying to open the floor repeatedly on a system that is finished, and a reroute or repipe ends that.

• InterNACHI puts a copper water line at about 50 years. (InterNACHI life expectancy chart)

Do not wait it out

A slab leak will not flood the house tonight, which is exactly why people leave them. Meanwhile it runs continuously, washes out the soil supporting the concrete, and adds to the bill every hour.

It is urgent rather than instant. Days are fine, months are not.