What are the hidden signs of a water leak?

A bill that rises with no change in how you use water. The City of Phoenix says to "pay attention to surges in your water bill. Unaccounted for month-to-month or year-to-year increases in cost or water consumption units may indicate a leak." Summer irrigation raises bills too, so compare against a cooler month. EPA's rule of thumb: "If a family of four exceeds 12,000 gallons per month, there could be serious leaks." If your bill is high and you can't explain it, our high water bill guide goes deeper.

A meter that moves when nothing is running. This is the most reliable sign, because it doesn't depend on what you can see. EPA's test: "Check your water meter before and after a two-hour period when no water is being used. If the meter changes at all, you probably have a leak." Here is how to run the water meter leak test.

Running or hissing water in a quiet house. With every fixture off, stand near the water heater, the bathrooms and the kitchen. A steady hiss or trickle inside a wall usually means a pressurized supply line is leaking. A toilet that refills by itself points to a leaking flapper instead; EPA notes an old flapper "can cause your toilet to flush on its own or silently leak thousands of gallons a year." If you can't tell whether the sound is normal, why you hear running water in the walls when nothing is on sorts the harmless sounds from the leaks.

A musty smell. EPA says you "may suspect hidden mold if a building smells moldy, but you cannot see the source." Its list of hiding places includes "areas inside walls around pipes (with leaking or condensing pipes)." A musty cabinet or closet with no visible water is worth a closer look.

Stains, bubbling paint and soft spots. Brown rings on a ceiling, paint that bubbles or peels, baseboards that swell, and drywall that feels soft all mean a wall or ceiling has been wet more than once. If the stain is on a ceiling, see what causes a water leak from the ceiling. EPA is clear that time matters: "if wet or damp materials or areas are dried 24-48 hours after a leak or spill happens, in most cases mold will not grow." A leak that stays wet for weeks doesn't get that chance.

Warm spots on the floor. A section of tile or slab that feels warm, especially with no radiant heating, can mean a hot water line is leaking under the slab. Slab leaks are a real issue here; see signs of a slab leak in Arizona and why slab leaks are common in Arizona.

Weak or uneven pressure. A leak can drop pressure, though it isn't the only cause. Phoenix Water Services says that if pressure "is consistently low, it could be indicative of a larger problem with the City's or the customer's water system." Check whether the whole house is affected before you suspect a pipe.

Rust, green crust or white scale on pipes and fittings. A pipe or valve that's crusted at a joint is or was weeping. That's common on older copper and on fittings in hard water areas. Pinhole leaks in copper pipes can spray a fine mist inside a wall for a long time before anything shows; see pinhole leaks in copper pipes.

Discolored or cloudy water. Rusty or brown water after a repair can be normal, but persistent discoloration can point to corroding pipes. See why tap water turns brown.

A leak in a buried line can show up in the yard. Phoenix advises: "Walk your yard. Soggy ground or sinkholes can be evidence of underground line leaks." A patch of lawn that stays wet or greener than the rest, a damp spot near the meter, or a wet driveway edge with no sprinklers running deserves a look. Is a wet lawn a sign of a broken water line? explains how to tell a water line from a sprinkler leak.

### Where hidden leaks usually are

You can't see them, but the failures tend to cluster:

• Behind a shower or tub. A failing shower valve or a cracked drain can soak the wall for months. See a leaking shower valve behind the wall.
• Under the slab. Hot and cold lines run under the floor in many Phoenix-area homes, and a slab leak often announces itself as a warm spot or the sound of running water. See why slab leaks are common in Arizona.
• Around the water heater. The tank, the connections and the relief valve line can all seep. See why a water heater leaks from the bottom.
• In the attic or ceiling. Supply lines, an air handler's condensate pan and a water heater installed in the attic can all leak above finished space.
• Underground. The service line from the meter to the house and the irrigation lines are buried, so the only clues are the meter, the bill and soggy ground.

Small leaks add up over time. EPA says the average household's leaks "can account for more than 9,300 gallons of water wasted every year," and that "nine percent of homes have leaks that waste 50 gallons or more per day." If you're a City of Phoenix water customer, the city offers a free water efficiency consultation that includes "a water meter read and inspection: used to identify and isolate outdoor leaks." It won't find a leak inside a wall, but it can rule out the yard.

Not every clue is a leak. The City of Chandler warns that meter movement "can also be caused by things like an automatic pool filler, a leaky irrigation valve, or an evaporative cooler." A dripping air conditioner condensate line, a sweating cold pipe and a monsoon roof leak can all leave stains that look like plumbing. Check why pipes sweat in summer if the wet spot is on a cold water line.

Appliance leaks are a common hidden source. Our pages on why a dishwasher leaks and why a washing machine leaks show where to look.

1. 1Run the meter test to confirm water is moving.
2. 2Close the main shutoff and test again. If the meter stops, the leak is inside; if it keeps moving, it's in the buried line before the house.
3. 3Check toilets, sinks, the water heater and the yard for the obvious sources.
4. 4If the meter still moves and you find nothing, have it located rather than opening walls at random.

HQ Plumbing & Air does leak detection using electronic equipment to find the source in walls, slabs and yards before anything is cut open. We're licensed and insured, we give free estimates, and you see the price up front. Water actively coming through a ceiling or floor is an emergency, and we take those calls 24/7. Whatever you decide, don't wait on a confirmed leak. That's how a small repair turns into a big one.