The bill arrives, it is double what it was, and nothing in the house is wet. Houston Water did not change its rates that month, nobody filled a pool, and the lawn is not greener. In almost every case like this the water is leaving the system somewhere you cannot see, and the meter can tell you where to look before anyone opens a floor.
A water bill that jumps with no visible leak means water is being used or lost somewhere hidden. Rule out the four usual suspects in this order: a toilet running silently, the irrigation system, a leak in the yard line between the meter and the house, and a slab leak under the floor. The meter test below tells you in ten minutes whether water is moving when everything is off, and the hot-water trick tells you which side of the system it is on.
- Check the bill's usage in gallons, not just the dollars. A one-time spike is different from a new, higher baseline.
- A running toilet can waste hundreds of gallons a day and makes almost no sound. It is the first thing to check.
- The meter test with everything off settles whether water is leaving the system at all.
- If the water heater runs when no hot tap is open, the leak is on the hot side, which in Houston usually means under the slab.
- Professional leak detection locates the spot by pressure and sound so the repair opens one place, not the whole floor.
First, read the bill properly
Look at the usage figure in gallons or CCF (one CCF is about 748 gallons), and compare it with the same month last year, not last month. Summer irrigation and houseguests change usage legitimately. What you are looking for is a step up that stayed up: two or three bills in a row above the old baseline with no change in the household. That pattern is a leak. A single high month followed by a normal one is more often a meter reading estimate being corrected, or a one-off like a hose left running.
Suspect 1: a toilet running silently
The flapper in the tank wears, the seal stops holding, and water trickles from the tank into the bowl around the clock. The fill valve tops the tank up a little at a time, so there is no obvious sound. A toilet doing this can waste 200 gallons a day or more.
The test takes five minutes: put a few drops of food coloring in the tank, do not flush, and come back after fifteen minutes. Color in the bowl means the flapper is leaking. Check every toilet in the house; the one in the guest bathroom nobody uses is a common culprit because nobody notices it. The fix is a new flapper or fill valve, which is a small repair.
Suspect 2: irrigation
Sprinkler systems leak at heads, at the valves and in the lines, and because they run at night nobody sees it. A stuck zone valve can run a zone every night for weeks. Turn the controller off entirely for a billing cycle if you can, or at least check each zone during a daytime manual run for heads that gush or spots that stay wet. The backflow preventer near the meter is another leak point, especially after a freeze.
Suspect 3: the yard line
Between the meter at the street and the point where the pipe enters the house there is a buried water line, often decades old, often galvanized steel or thin-wall copper in older Houston neighborhoods. It leaks into the soil where nobody sees it. Signs: a patch of lawn that is greener or softer than the rest along the line, water pooling near the foundation or the meter box with no rain, or a drop in pressure at the house.
Suspect 4: a slab leak
Most Houston homes sit on a concrete slab with the water lines running through or under it. The clay soil moves with the seasons, the pipe flexes at the same spot thousands of times, and eventually a pinhole opens. On the hot side, a warm patch on the floor is the classic sign; on either side, the signs are a bill that climbs, the sound of water running when nothing is on, a damp spot on a floor or at the base of a wall, or a water heater that keeps firing because hot water is leaving the system all day.
The ten-minute meter test
- Turn off every faucet, appliance and the irrigation. Make sure no toilet is refilling and the ice maker is off.
- Find the meter, usually in a box near the street. Lift the lid and note the reading, including the small leak indicator (a triangle, a star or a small dial) if there is one.
- Wait ten minutes without using any water.
- Look again. If the leak indicator turned or the reading changed, water left the system while everything was off. That is a leak, not usage.
- Now close the main shutoff valve at the house, where the line comes in, and watch the meter again for ten minutes. If it still moves, the leak is between the meter and the house: the yard line or the irrigation. If it stops, the leak is inside or under the house.
Write the readings down. A plumber will want them.
The hot-water trick
If the meter test says the leak is in or under the house, go to the water heater. With everything off, close the cold inlet valve on top of the tank. Check the meter again. If it stops moving, the leak is on the hot side: a hot line under the slab or in a wall. If it keeps moving, the leak is on the cold side. This one check cuts the search area in half and is the first thing a leak detection technician does.
What professional leak detection actually does
Detection is a process of elimination with instruments. The technician isolates sections by closing valves and holding pressure on each one: hot against cold, house against yard, supply against drain. The section that cannot hold pressure has the leak. Then listening equipment traces along that line until the sound of escaping water peaks, and that spot is marked on the floor or the lawn. For a drain-side leak, a camera goes through the pipe and shows the crack directly.
The result is a marked location and a repair price for that location. A slab leak is then fixed by tunneling under the slab to the spot, by opening the floor above it, or by rerouting that line overhead through the attic and abandoning the section under the slab. Which one depends on where it is and how many leaks the line has had; a line on its third slab leak is usually rerouted rather than patched again.
What it costs to wait
A pinhole under a slab wastes water, but the larger cost is what the water does: it saturates the soil under the foundation, which in Houston clay can move the slab and crack walls and tile. On the hot side it also runs the water heater constantly. A yard line leak undermines the driveway or the meter box. None of these get cheaper by the month.
Quick reference: which suspect is it?
| What you see | Likely cause | Next step |
|---|---|---|
| Bill up, meter moves, stops when the house main is closed | Leak inside or under the house | Hot-water trick, then leak detection |
| Bill up, meter moves even with the house main closed | Yard line or irrigation | Shut the irrigation off and retest; if still moving, the yard line |
| Bill up, meter does not move with everything off | Not a leak: usage, a toilet that runs only sometimes, or an estimated reading | Dye-test the toilets, check the bill history, ask the utility about estimates |
| Warm spot on the floor, heater runs constantly | Hot-side slab leak | Leak detection, then tunnel, open or reroute |
| Green or soft strip of lawn toward the street | Yard line leak | Leak detection on the service line |
| One toilet refills on its own | Flapper or fill valve | Replace the part |
Frequently asked questions
Can a water bill go up without a leak?
Yes. New household members, a new appliance, summer irrigation, a filled pool or an estimated reading corrected the next month all raise a bill. A leak shows as a sustained rise with no change in habits, confirmed by the meter moving when everything is off.
How much water does a running toilet waste?
A toilet with a worn flapper can waste 200 gallons a day or more, silently. Two in a house can double a bill. The dye test takes fifteen minutes and the repair is a small part.
Where is my water meter?
In most Houston homes it is in a box at the front of the property near the street or sidewalk, under a metal or plastic lid. Some newer meters are read remotely, but the dial still shows flow.
What is a slab leak?
A leak in a water line that runs under or through the concrete slab foundation. Houston's clay soil moves the slab with the seasons, which stresses the pipe. Signs are a rising bill, a warm floor spot, the sound of running water and a heater that will not stop.
Does leak detection damage the floor?
No. Detection isolates the line by pressure and locates the leak with listening equipment from above the floor. The floor is opened only at the marked spot if that repair method is chosen, and often not at all if the line is rerouted.
Will the water utility reduce my bill for a leak?
Many utilities, including the City of Houston, have a leak adjustment process for a repaired leak with a plumber's invoice. Keep the invoice and ask.
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