What Is Water Heater Leak Detection?
Water heater leak detection is a paid visit for leaks you can't find on your own: damp floors or walls near the heater, wet drywall behind a closet, or a water meter that moves with every tap off. We isolate the heater and its lines, take moisture readings and pressure-test where needed until we know the source.
Most water heater leaks are easy to spot once you look. A drip from a fitting, a wet drain valve, water from the relief pipe. If that's your situation, our free guide to finding where your water heater is leaking walks you through it in a few minutes, and you may not need us at all.
This page is for the other kind: the heater looks dry, but the floor beside it is damp, a stain behind the closet keeps growing, or the water bill jumped. Those leaks hide in walls, under floors or in lines running past the heater, and finding them takes a method, not a flashlight.
Signs You Need Leak Detection, Not Just a Look
- Damp flooring or baseboards near the heater with no water on the tank or its fittings.
- Wet or stained drywall on the far side of a water heater closet or garage wall.
- A water meter that moves when every tap, toilet and irrigation zone is off.
- A pan that fills slowly when the heater itself looks dry.
- Soft or swollen floor in a mobile home's water heater closet, with no obvious drip.
- A warm spot on the floor or the sound of running water when nothing is on, which can point to a hot line leaking under the slab.
The First Test: Is It the Heater or the House?
Before anything gets opened up, we answer one question: is the water coming from the heater and its hot lines, or from somewhere else in the house plumbing? The water meter answers most of it.
- Everything off. All taps, toilets, the ice maker, the softener and irrigation are off, and nothing is running.
- Read the meter. Most meters have a small leak indicator, often a triangle or small dial, that turns with even a slow flow. We note whether it moves.
- Close the cold valve at the heater. This stops water feeding the tank and the hot lines past it.
- Read it again. If the indicator stops, the leak is on the heater side: the tank, its fittings or the hot piping. If it keeps turning, the leak is somewhere else on the house plumbing.
You can do this test yourself. If you're not sure where the cold valve or the meter is, our shut-off guide shows the valve, and the meter is usually in a box near the street.
Tip: A softener or a toilet with a worn flapper can move the meter too. That's why we shut those off first. A running toilet is a cheap fix, but it can send you hunting for a leak that isn't there.
How We Track a Hidden Leak
Once we know which side of the plumbing the water is on, we narrow it down. Every house is different, but the methods are the same.
Moisture readings
We check drywall, baseboards and flooring at points around the heater and map where readings are highest. Water spreads, so the wettest point is often close to the source.
Isolating lines
We close valves one at a time, at the heater, the recirculation line and branch lines, and watch the meter after each. The leak lives on the line that stops it.
Pressure checks
We measure house pressure and, where it helps, test an isolated section to see if it holds. A section that loses pressure is leaking.
Why is high water pressure part of a leak check?
Pressure that's too high wears out fittings, connectors and the relief valve faster. If we find high static pressure or a closed system with no expansion control, we'll say so, because fixing the leak without fixing the cause can mean another leak later. Our expansion tank page explains how that part fits in.
Leak Detection in Mobile Homes
Mobile and manufactured homes make up roughly 46% of local housing, and they hide leaks in their own way. Water lines run under the floor, inside the insulated belly of the home. A leak there can soak insulation and particleboard for weeks before anything shows inside, except maybe a soft spot near the water heater closet or a higher bill.
We check the heater closet floor, the lines where they pass through it, and what we can safely reach from outside. If the belly has to be opened, we'll tell you first. For heater work in these homes, see our mobile home water heater service.
What You Get From the Visit
- The source, or the line it's on, explained in plain words.
- Photos and written findings on request, which help if you talk to your insurance agent.
- A repair price before any repair work starts.
- Any cause behind the leak, such as high pressure or a missing pan, so it doesn't come back.
If the leak caused damage, our insurance and water heater leaks page explains how policies usually treat it, and our post on cleaning up water damage after a leak covers drying out. To catch the next one early, a drain pan with a leak sensor is worth a look.
What does leak detection cost?
It depends on how hidden the leak is and how much line has to be tested, so we price it after we hear what you're seeing. The repair afterward is a separate line. For context, Angi lists about $646 as the Apache Junction average across all kinds of water heater repairs, with most between $422 and $1,196. Our repair cost page breaks down what drives the price.
When to Call Right Away
If water is spreading, close the cold valve at the heater or the main shut-off and turn off the heater's power or gas. If water is near outlets or the electrical panel, keep clear and shut off that power at the breaker only if you can reach it from a dry spot. Our emergency water heater service runs 24/7.
For leaks you can see, our water heater leak repair service and the wider repair service handle the fix. For the leak you can't find, phone us at +1 480-863-0807 and tell us what you're seeing.
Water Heater Leak Detection FAQs
Can a hidden leak stop on its own?
It can seem to. A drip may slow when the tank cools or the house pressure drops overnight, then come back with the next heating cycle or a long shower. A stain that dries and returns, or a meter that moves now and then, still points to a leak. Keep notes of when you see water; the pattern helps narrow the source.
Why is my water bill high but I can't see a leak?
Common hidden causes are a running toilet, an irrigation valve that doesn't close, a softener stuck in a cycle, or a line leaking under the slab or inside a wall. A meter that moves with everything off confirms water is going somewhere. Check toilets and irrigation first, since they're the easiest to rule out.
What should I do while I wait for a leak check?
If water is pooling, close the cold-water valve above the heater and turn off its heat. Move boxes and rugs out of the wet area, run a fan, and take a few photos of the stain or puddle with the time noted. Don't cut into drywall or flooring yet; an open wall can hide where the water first showed up.
Will leak detection damage my walls or floors?
Usually only a little, and often not at all. Moisture readings and line tests are done without opening anything. When a wall or floor does have to be opened to confirm or reach the leak, the opening is kept as small as possible, and you're told where and why before anything is cut.
Is it worth paying for leak detection on an old water heater?
Sometimes the tank itself is the answer and no detection is needed. But if the heater looks dry and something nearby is wet, replacing it on a guess could leave the real leak running. A short visit to confirm the source costs far less than a new heater installed for the wrong reason.