Under-Slab Drain Line Repair in Phoenix

The other pipes under the floor

A supply line is under pressure, so a hole in it leaks around the clock. Drain lines carry waste water away by gravity and only leak while water is flowing. That difference changes everything about how a drain problem is found. The water meter shows nothing, the house holds pressure, and yet the floor near a shower is damp or the room smells of sewer. In Valley homes the drains beneath the slab are usually black ABS plastic in houses from the 1970s onward and cast iron in older ones, both feeding a main line that leaves toward the street.

Symptoms that point to a drain

Watch for signs that appear only after water is used: a damp baseboard after showers, a musty or sewer smell in one room, slow drains in several fixtures at once, gurgling from a toilet when the washer empties, or floor tiles near a bathroom starting to lift. Cast iron rusts and scales from inside until it cracks along the bottom of the pipe. ABS can separate at glued joints or crack where the ground has moved. Shifting clay can also create a belly, a sag where water and waste sit instead of draining.

Camera inspection and the hydrostatic test

A waterproof camera on a cable is fed through a cleanout and down the line, showing roots, cracks, offset joints, scale and standing water. A locator on the surface picks up the camera head so the damage can be marked on the floor above it. To prove whether the system is actually leaking, a hydrostatic test plugs the main line and fills the drains with water to a fixed level; if the level drops, the system is losing water under the slab. Sections can be tested one at a time to narrow the search.

Repair choices for drain lines

A single break is usually repaired by opening the slab over it, much like a supply-line spot repair but often wider because drain pipe is larger and has to hold its slope. Longer failing runs can be replaced with a new section, or sometimes rerouted where the layout allows. Older cast iron in parts of Phoenix and Glendale tends to fail in several places at once, which makes a camera survey of the whole system worth doing before deciding. If the meter was spinning as well, pair this with supply-line detection, and if the leak is outdoors past the foundation, see main water line repair.

How long does it take? Inspection and testing usually take a few hours; repairs typically take one to three days depending on how much line is replaced.

Frequently asked questions