The leaks that cost the most are the ones nobody sees. A slow drip in a wall, a pinhole in a supply line under a floor or a failing seal behind a tub can run for months. Finding them starts with a few tests that anyone can do and ends, usually, with a plumber's tools.
Step 1: the water meter test
Turn everything off.
Shut off all taps, the dishwasher, washer and ice maker. Make sure nobody flushes a toilet.
Read the meter.
Find the meter, usually near the street or in the basement, and note the reading or the small dial that spins with low flow.
Wait and read again.
Wait fifteen to thirty minutes without using water, then read it again.
Compare.
If the reading moved or the dial is spinning, water is leaking somewhere in the system.
If you shut off the main valve and the movement stops, the leak is on the house side of the valve. Photograph your readings. If the meter does not move, the leak, if any, may be too small or intermittent.
Step 2: check the bill
A bill that rises without a change in use is a clue. Compare the last few months, and look for jumps that do not match guests, a new appliance or a season with more laundry. Some utilities offer leak alerts or online usage graphs, which can show water running overnight.
Step 3: room-by-room checks
| Where to look. | What to check. | What it might mean. |
|---|---|---|
| Toilets. | Add a few drops of food coloring to the tank and see if it shows in the bowl without flushing. | Worn flapper leaking into the bowl. |
| Under sinks. | Dry the pipes with a towel and feel for dampness over time. | Failing supply line or trap. |
| Around the water heater. | Look for rust, drips or a damp floor. | Leaking tank or fitting. |
| Behind appliances. | Pull out the washer, dishwasher and fridge to inspect hoses. | Split hose or ice maker line. |
| Ceilings below bathrooms. | Look for stains or soft spots. | Tub, shower or toilet seal leaking. |
| Floors. | Feel for warm spots, cupped boards or soft areas. | Leak under the floor or in a slab. |
Sound helps too. Stand in a quiet house and listen for hissing or running water when nothing is on. A thin, steady hiss from a wall points to a pressurized line.
Signs of a leak you cannot see
- Musty smell with no visible source.
- Peeling paint or bubbling wall surface.
- Warm spots on the floor, which can mean a hot water leak.
- Cracks or cupping in flooring.
- Higher humidity in one room.
- Mold or mildew in corners.
Our pages on slab leaks, crawl space water and frozen pipes cover the places where leaks hide in houses of different types.
When to call a plumber and when to call us
A plumber finds and fixes the leak. We dry and repair the damage it left and can use moisture meters and thermal cameras to show where the water traveled. Baltimore County says a plumbing permit is required for all plumbing and gasfitting work and that only a county licensed plumber or gasfitter contractor can apply for it. Plan for both.
Utilities and the Catonsville meter
Baltimore County's website says Baltimore City is responsible for water service in the county, and the city draws from the Liberty, Loch Raven and Prettyboy reservoirs. If your meter shows unexplained use, the leak is on your side of the meter and the city or your plumber can help you confirm.
A main line break outside your property is a city issue. A leak inside the house or between the meter and the house is yours. Knowing the difference saves a call.
Source type: Baltimore County government water and sewer pages, Baltimore City Department of Public Works.
What to do while you wait
If you find a leak, shut off water at the fixture or the main. Move belongings away. Photograph the area. Do not poke or cut into walls unless you know what is behind them. Call a plumber for the repair and us if there is wet material. Early drying saves finishes and often cuts the cost of the whole job.
Hidden leaks cross county lines in the same way. For Howard County addresses, see the Elkridge page, and for city properties, see the Baltimore page.
Professionals trace hidden water with moisture meters and thermal cameras, the tools the ANSI/IICRC S500 standard describes for moisture mapping. A quick check with them is often cheaper than opening walls to look.
Found a leak or a wet spot?
Call the 24/7 line. We trace where the water went.
Catonsville hidden-leak questions
Often near the street in a meter box or inside near where the line enters. Baltimore City supplies water in the county, so contact the city if you cannot find it.
A silent leak from the tank into the bowl can run constantly and raise a bill. The dye test shows it.
Yes, for the repair. A plumber finds and fixes the leak, and a restoration company handles the wet materials.
The source may be a drain, a drip that is too small to register or condensation. A moisture reading and an inspection help.