The sound of running water with every fixture off usually means water is moving somewhere it shouldn't. The most common cause is a toilet leaking from the tank into the bowl; the next is a hidden supply line leak in a wall, ceiling or under the slab. Check your water meter with everything off. If it moves, water is leaking, and a toilet dye test tells you whether the toilet is the cause.
A steady hiss or trickle when every faucet in the house is off is worth taking seriously. Sometimes it’s harmless, like a toilet refilling. But it’s also one of the most common ways people first notice a hidden leak in a wall or under a slab, long before a stain or a big bill. Here’s how to work out what you’re hearing in about 10 minutes.
Common causes of a running water sound
| Cause | What it sounds like | How to check |
|---|---|---|
| Toilet leaking into the bowl | Faint trickle, or the tank refilling by itself every so often | Dye test (below) |
| Hidden supply line leak | Steady hiss that doesn’t stop, often louder at night | Meter test |
| Slab leak | Running water or hissing heard through the floor | Meter test, then shutoff and water heater tests |
| Water softener or water heater cycling | Runs for a while, then stops | Check whether the unit is in a regeneration or heating cycle |
| Irrigation valve not fully closing | Water sound near the main line or outside wall | Close the irrigation shutoff and listen again |
| High water pressure | Noise and banging in the pipes | Pressure gauge on an outside faucet |
Step 1: The 10-minute meter test
- Turn off every faucet, shower, washer, dishwasher and ice maker. Make sure nobody flushes.
- Find your water meter and look at the leak indicator, usually a small triangle, star or dial.
- Watch it for 10 minutes, or note the reading and check again after an hour or two.
- If it moves, water is leaving the system. If it’s perfectly still, the sound is probably not a supply line leak.
The EPA’s WaterSense program estimates that household leaks can waste nearly 10,000 gallons a year in an average home, and that 1 in 10 homes has leaks wasting 90 gallons or more a day (EPA WaterSense Fix a Leak Week). A running sound you can hear usually means a leak at the larger end of that range.
Step 2: Rule out the toilets
Toilets are the most common cause of a running sound, and the cheapest to fix.
- Put a few drops of food coloring in each toilet tank.
- Wait 15 minutes without flushing.
- If color appears in the bowl, the flapper or fill valve is leaking.
Replacing a worn flapper usually stops it. Then repeat the meter test; if the meter still moves, something else is leaking too.
Step 3: Narrow down where the sound is coming from
- Close the main shutoff in the house. If the meter still moves, the leak is in the buried line between the meter and the house. See how to find an underground water leak.
- Close the cold water inlet on the water heater. If the meter stops, the leak is on the hot side, which in a slab home often means a hot water line under the floor.
- Close the irrigation shutoff if you have sprinklers, and check again.
- Listen at the quietest time of day. Put your ear to the floor, a wall or a closet near the plumbing. The sound is usually loudest closest to the leak.
- Feel the floor. A warm spot on tile or wood over a running sound is a strong sign of a hot water slab leak.
Why you can hear a leak you can’t see
Water escaping from a small hole in a pressurized pipe makes noise: a hiss from the pipe itself and a rushing sound as it hits soil, concrete or the wall cavity. In a slab home, that noise travels through the concrete, which is why many homeowners first notice a slab leak as a running sound in a quiet room at night.
That same sound is what professionals use to find it.
How a leak you can hear gets pinpointed
Professional slab leak detection turns the sound into an exact spot:
- Isolation and pressure testing confirm which line is leaking: hot, cold or the service line.
- Line tracing maps where that pipe runs under the floor or in the wall.
- Acoustic ground microphones are moved along the line; the point where the sound is loudest marks the leak.
- Thermal imaging confirms a hot water leak by the warm bloom on the floor.
- Tracer gas finds quiet leaks in plastic pipe that don’t make much noise.
The spot is marked so the plumber makes one small opening. More detail on each tool is in how professional leak detection works.
When to call
Call if the meter moves after you’ve ruled out the toilets, if you hear running water under the floor, if a floor feels warm, or if your water bill has jumped. A hidden leak running around the clock wastes water, can raise your energy bill if it’s on the hot side, and can soak framing, flooring and soil under the slab.
We find these leaks across Bargersville and Johnson County, including Center Grove, Greenwood and Whiteland.
Still can’t find it?
Our slab leak detection pinpoints the leak without tearing things up, so the repair starts in the right spot.
Frequently asked questions
Is it normal to hear water running in pipes when nothing is on?
Not for long. A few seconds after a toilet refills or an appliance finishes is normal. A steady hiss or trickle with everything off means water is flowing somewhere: a toilet, a sprinkler valve, a water softener or water heater cycle, or a leak.
How do I check if a toilet is causing the running water sound?
Put a few drops of food coloring in the tank, wait 15 minutes without flushing, then look in the bowl. If color shows up, the flapper or fill valve is leaking and the toilet is wasting water.
Can you hear a slab leak?
Often, yes. A pressurized line leaking under a concrete slab can make a hissing or running sound you hear through the floor, especially at night when the house is quiet. Leak detection uses acoustic equipment to find the spot where that sound is loudest.
What if the meter doesn't move but I still hear water?
The sound may be a drain carrying water from another fixture or appliance, water hammer or pipe expansion, a sprinkler or neighbor's line nearby, or a leak that's only intermittent. Repeat the meter test at a different time of day.