You can run the first test for a slab leak yourself, before you ever pick up the phone, and all it takes is a flashlight, a pencil and a little patience. Houses built on concrete slabs have supply lines running under the floor, and when one of those lines lets go, the water goes into the ground where you cannot see it. The water meter does not care where the water is going. It just counts. That makes it the most honest witness on the property, and here is how to ask it what is going on.
Find the meter and the little dial that matters
On most homes the meter sits in a concrete box near the street or the sidewalk, with a lid you can pry up with a screwdriver. Watch your fingers, and give it a second in case something has moved in under there. Inside you will see the meter face, with a big sweep hand or a row of numbers, and on many meters a small triangle, star or tiny wheel that spins with even a trickle of flow. That small one is the leak indicator, and it is the part you want to watch.
If the face is fogged or covered in dirt, a damp rag usually clears it. If you cannot find the box at all, or the lid is stuck, do not fight it. Just let us know when you call, because we will check the meter anyway. Write down the numbers on the face before you do anything else. That reading is your starting point for the second half of the test, and it is the most useful thing you can hand us when we arrive.
Turn everything off and watch it
Now go back inside and make the house quiet. Every faucet off, no toilets flushing, the dishwasher and washing machine idle, the sprinklers shut down at the controller, the ice maker and any water softener not in a cycle. Make sure the water heater is not in the middle of refilling after somebody’s shower. You want nothing in the house asking for water.
Then go back out and look at the leak indicator. If it is sitting still, that is good news. If it is turning, even slowly, water is going somewhere. For a second check, leave the house alone for a good while without using any water at all, then read the numbers again and compare them to what you wrote down. Any change means water moved through the meter while nobody was using it. One common culprit before you panic is a toilet that runs quietly. Put a few drops of food coloring in the tank, wait without flushing, and if the color shows up in the bowl, the flapper is leaking and that may be all your meter is seeing.
Close the main and look one more time
If the meter is still moving and the toilets check out, the next step narrows it down further. Find the main shutoff valve for the house, usually where the supply line comes up out of the ground near the front or side wall, and close it. Then check the meter again.
If the indicator stops when the house is shut off, the leak is on the house side of that valve, which on a slab home means somewhere in the piping inside the walls or under the floor. If it keeps turning with the house valve closed, the leak is more likely in the line running from the meter to the house, out in the yard. Both are worth a call, but they are very different jobs, and knowing which side you are on saves time from the first minute. One more thing while you are at that valve: if it will not budge, do not force it with a pipe wrench. A stuck main shutoff is its own problem, and a valve that gets worked now and then is far less likely to freeze up on you when you actually need it.
The warm floor and the sound of running water
The meter is not the only witness. A slab leak on a hot water line often shows up as a warm spot on the floor, the kind you notice walking barefoot across tile or when the dog suddenly picks a new favorite place to lie down. Carpet that feels damp for no reason, a musty smell, or new cracks in tile or flooring can all point the same direction.
Sound is another clue. With everything off and the house quiet, stand in the rooms where the supply lines run and just listen. A faint hiss or the sound of water running when nothing is on is worth taking seriously. On the hot side, a water heater that seems to be running and refilling constantly when nobody is using hot water tells a similar story. None of these prove a slab leak on their own, and none of them tell you where under the floor the leak actually is. They tell you it is time to have somebody find it properly before the water does more damage.
How we find the spot before any concrete comes up
This is the part people worry about, picturing their whole floor jackhammered while somebody hunts around. It does not work that way. We start with pressure testing to confirm which line is losing water, hot or cold, and whether it is under the slab at all. Then we use acoustic listening equipment, which picks up the sound of pressurized water escaping through concrete, and thermal imaging, which shows the warm trail a hot water leak leaves under the floor.
Used together, those tools point at one small patch of floor, and that is where the opening goes, instead of a row of test holes across the kitchen. The general slab leak repair page explains the equipment in more depth. From there, the choice is between repairing the pipe right at that spot or, if the line under the slab is failing in more than one place, rerouting it overhead through the walls and attic and leaving the old one abandoned in the concrete. You can read how we handle both on our slab leak repair and detection page for Redlands, and our leak detection page covers leaks that are not under the slab.
Questions about the meter test
How long should I watch the meter?
Give it a good half hour with every fixture off and nobody using water. A fast leak shows right away. A slow one may barely move the dial, so write down the reading at the start and again at the end instead of trusting your eye, and note the time between them.
Can a slab leak be on the cold side as well as the hot side?
Yes, either one. A hot side leak is the one that can warm a patch of floor and keep the water heater running. A cold side leak gives off no warmth at all, so the meter is often the only early sign. Knowing which side it is on is a big part of how the search gets narrowed down.
Will my water bill show a slab leak?
Sometimes, if it runs fast enough and long enough. A small one can hide inside the normal ups and downs from month to month, which is why the meter check is worth doing on its own instead of waiting for a bill to jump. If the bill does jump and nothing in the house changed, check the meter that same day.
If your meter moved and you are not sure what to do next, write down both readings and how long apart you took them. Send them over or call (909) 888-8736, and we will take it from there.