Drain leak detection in Tucson, AZ

Drain leak or water supply leak: how to tell

Supply pipes hold pressure all day, so a supply leak never stops and the meter shows it. Drain pipes are empty until someone uses a fixture. A drain leak releases water for the few minutes that water is flowing past the bad joint, then stops.

That gives a drain leak a recognizable pattern: the meter stays still, the damage appears or worsens after showers, laundry, or dishwashing, and the area may partly dry between uses. If that matches what you're seeing, the problem is very likely in the drain system.

Signs of a leaking drain pipe

• A stain or damp patch that grows after a fixture is used and then pauses.
• Water or staining on the vanity or kitchen cabinet floor with dry supply connections.
• A ceiling stain below an upstairs bathroom or laundry room.
• A sour, sewer-like, or musty smell in a cabinet, wall, or room.
• Gray or soapy residue where the water appears. Drain water carries soap, grease, and lint.
• Drain flies or small gnats around a wall or cabinet.
• Dampness at the base of a wall behind the washing machine, especially during the drain cycle.
• Loose or damp tile next to a tub or shower.

Where drain pipes leak in a house

• P-traps and slip joints under sinks. The nuts loosen and the washers harden.
• Tub and shower drains. The connection between the drain fitting and the pipe below, and the tub overflow.
• The kitchen line. It carries grease and food, clogs most often, and leaks at joints when water backs up and stands in it.
• The washing machine standpipe and its trap inside the wall. A washer pumps out fast, and a partial clog makes the standpipe overflow inside the wall cavity.
• Glued plastic joints that were never fully seated or cemented.
• Old cast iron and galvanized drain pipe, which rusts through along the bottom.
• Drain pipes under the slab, cracked or separated where the soil has settled.

How we find a leaking drain pipe

1. Rule out supply. A meter test and a pressure test confirm that no pressurized pipe is leaking. This step keeps a supply leak from being mistaken for a drain leak.
2. Map the moisture. A moisture meter and thermal camera show where the wet area is and how far it extends.
3. Run one fixture at a time. Each sink, tub, shower, and appliance is run alone, with a measured amount of water, while the wet area is watched. The fixture that makes it respond is on the leaking line.
4. Dye test. A different color of dye in each fixture shows which one's water reaches the stain.
5. Fill test. The drain is plugged below the suspect section and filled, so water stands against every joint. A slow leak that a quick flow passes over shows up this way.
6. Camera inspection. A small camera is run through the drain to look at joints, cracks, and sags, and its position is located from the surface.
7. Mark and explain. The leaking joint or section is marked, and you're told which line it is and what was seen.

For drains under a ground-floor slab, the fill test is done from the cleanout with the line plugged, and the branches are isolated one by one. That overlaps with the testing described under sewer line leak detection, which covers the main line from the house to the street.

Roof vent leaks in monsoon season that look like drain leaks

Every drain system has vent pipes that rise through the roof. Where each pipe passes through the roof, a flashing with a rubber or sealant collar keeps rain out.

Years of Tucson sun dry out and crack that collar. When a monsoon storm arrives, rain runs down the outside of the vent pipe, follows it through the attic and into the wall, and appears as a stain right beside the bathroom or kitchen plumbing.

It looks exactly like a drain leak. It's in the plumbing wall, it's next to the drain stack, and it leaves a similar stain.

The difference is timing: it appears after rain and has nothing to do with using the fixtures. People have had drain pipes opened up and replaced for a problem that was a cracked roof collar.

The way to avoid that's to test before repairing. If the fixtures are run and filled and the drain holds, and the stain only grows after storms between mid June and the end of September, the roof penetration is the source. We check the vent line as part of the investigation and tell you when the answer is on the roof.

Air conditioning adds a related problem. Many AC condensate lines in Tucson homes discharge into a bathroom sink drain or a dedicated drain in the wall. They carry water all summer, and that connection can leak or back up with no fixture in use.

What affects the cost of drain leak detection

• How many fixtures could be responsible. One sink is quick. A bathroom group and a laundry room on the same wall take longer.
• Where the pipe is. Under a sink is simple. Inside a wall, above a ceiling, or under the slab takes more testing.
• Whether the leak is easy to trigger. Some only leak when the pipe runs full, such as a washer discharge or a draining tub.
• Access for testing. A cleanout or an accessible trap arm makes plugging and filling easier.
• Partial clogs. A slow drain may need clearing by a drain cleaning company before it can be inspected properly.

When a drain leak is an emergency

The quick fix for a drain leak is simple: stop using the fixture that feeds it. Unlike a supply leak, it stops when you stop.

It becomes urgent when waste water is coming through a ceiling, when it's wetting electrical fixtures or outlets, or when the leak is on a line that carries toilet waste. Turn off the breaker for any wet electrical fixture, keep people away from contaminated water, and stop using the bathrooms on that line. Also treat it as urgent if water backs up from one fixture into another, since that means a blockage is forcing water out at the joints.

How to prepare for drain leak detection

• Do the meter test with everything off, so we know supply isn't involved.
• Stop using the suspect fixture for a day beforehand if you can. A drier starting point gives clearer results.
• Keep a short log: which fixture was used, and when the damp appeared.
• Empty the cabinets under sinks and clear access to the washer and any cleanouts.
• Note whether it has rained recently.

Leak Detective finds the leak and doesn't repair it. A plumber replaces the joint or section.

After the repair, run the fixture hard, with a full tub or a full wash cycle, and check that the area stays dry. Moisture readings should fall over the following days.

If the damage is concentrated around a shower, tub, or toilet, see bathroom leak detection for the fixture-specific tests. Drain testing is a regular part of our Tucson leak detection service, because many of the damp walls and ceilings we're called to have nothing to do with the supply pipes.