Most hidden leaks give themselves away to a simple meter test, and closing the main valve tells you whether the water is escaping inside the house or underground. From there a plumber can usually narrow it down, and when a buried leak leaves no sign at the surface, a leak detection company's listening equipment can pinpoint it before anyone digs.
How can I tell if I have a hidden water leak?
Use your water meter. Turn off every tap and appliance, including the irrigation timer and the ice maker, write down the reading, and check it again two hours later without using any water. If the reading has moved, water is leaving the plumbing somewhere. A winter water bill well above your usual one points the same way.
By the EPA's rule of thumb, a family of four using more than 12,000 gallons a month in winter may have a serious leak.
Is the leak inside my house or in the yard?
Close the main shutoff where the water line enters the house, then watch the meter. If it still moves, the leak is underground, between the meter and that valve. If it stops, the leak is inside the house: a toilet, a faucet, the water heater, or a pipe in a wall, a ceiling or the crawlspace.
One catch: an irrigation line often tees off the service before it reaches the house, so close the irrigation shutoff too. In Kenmore's Moorlands neighborhood this July, Malikai and Joshua found a leak on just that kind of tie-in and capped the irrigation line about a foot and a half down.
How do I check my toilet for a silent leak?
Put a few drops of food coloring in the toilet tank, don't flush, and look at the bowl ten minutes later. If color has crept into the bowl, water is slipping past the flapper and down the drain all day. A new flapper usually fixes it, and it is one of the cheapest leaks in the house to stop.
Do I need a leak detection company, or can a plumber find the leak?
Often a plumber can. A meter test, a pressure test and a careful walk along the line find most leaks. When a leak is buried under a lawn, a patio or a slab and leaves no sign at the surface, a leak detection company's listening equipment can pinpoint the spot. On an old line, replacing it can beat the hunt.
When a leak has already been pinpointed and marked, we dig right there. Under a Portage Bay patio, the marked leak turned out to be a cracked irrigation fitting, and Nick and Jeremy lifted the pavers, replaced the failed section and found no further leaks. Between Mill Creek and Bothell this June, Malikai and Theoren repaired a service line leak within hours of a leak detection company confirming it, as the homeowner wrote in a Google review:
"Big shout out to Malakai and Joshua for a quick and fair estimate of repairs for a small leak in our service line, and to Malakai and Theo for doing the repair work just a couple days later (literally hours after getting confirmation of the leak from a leak detection company). I couldn't have been more pleased with the level of service and professionalism exhibited by this team."
Ethan M., Google review
Why is my ceiling stained when the meter test shows no leak?
Because the leak is probably in a drain, not a supply pipe. Water in a drain has already passed the meter, so a drain leak only drips while someone uses the fixture above. A stain that grows after showers usually means a cracked drain or a failed shower seal, and it needs a look from below.
In Bellevue this February, Ashton and Joseph P. opened the ceiling below a shower and replaced its broken ABS drain. In Bothell's Wayne neighborhood, Nick and Jeremy traced a leak in a garage wall to a screw driven through a drain line, and repaired the pipe.
Can a leak hide in my crawlspace without any sign upstairs?
Yes. Nobody goes into a crawlspace on a normal day, so a dripping pipe can soak the insulation and subfloor before anything shows inside. Watch for a musty smell, a meter that creeps, damp or sagging insulation, and, when the leak is on a hot water line, a water heater that seems to run more than it should.
North of Bothell last November, while replacing a water heater, Jeremy found a hot water line leaking in the crawlspace under the kitchen. In Brier this March, Malikai and Joshua traced water damage to a broken washing machine drain trap and repaired it.
How much water does a small leak waste?
More than most people guess. The EPA says the average household's leaks waste more than 9,300 gallons a year, and a faucet dripping once a second wastes over 3,000 gallons a year on its own. A toilet with a worn flapper can silently lose thousands of gallons a year, so the dye test is worth ten minutes.
What should I do the moment I find a leak?
Stop the water first. Close the shutoff under the fixture if there is one, or the main shutoff where the line enters the house, and turn off the water heater if hot water is involved. Then move what you can out of the wet area, take photos for your insurer, and call a plumber.
Not sure where your main shutoff is? Our fall plumbing checklist shows how to find it before you need it.
Our Recommendation
Run the two-hour meter test whenever the bill jumps, and do the dye test on every toilet while you are at it. If the meter keeps moving with the house valve closed, call before the leak finds its way to the surface. On an aging galvanized or black poly service line, that first leak is usually the signal to replace the line rather than patch it.
Get a Leak Found
Call for a free estimate, or request a callback. We find and fix leaks inside the house and out, and when a leak has already been marked, we dig right there.
Related: leak detection · main water line repair · who pays for a water service leak · signs your water line is failing · toilet repair · a crawlspace drain repair in Lynnwood · hose bib repair