A sewer line pressure test, often called a hydrostatic or sewer water test, plugs the drain line, fills it with water and watches whether the water level drops. If it drops, water is leaking out of the pipe somewhere, usually under the slab or in the yard. It is a clear pass or fail check for leaks you cannot see.
A camera shows what the inside of a pipe looks like. A pressure test shows whether the pipe actually holds water. The two work together, and for homes on a concrete slab, the pressure test is often the only reliable way to confirm that a drain line under the floor is leaking.
When a Pressure Test Makes Sense
- Signs of a slab leak: cracks in the floor, a floor that feels higher in one spot, musty smells, or a sewer smell with no clear source.
- Before buying a slab home: a sewer water test can uncover leaks under the house that a camera alone might miss.
- After a repair: to prove new pipe and connections hold water before the trench is filled in or the permit inspection.
- Foundation work: foundation repair companies often want drain lines tested, since leaking sewer water under a slab can wash out soil and move the foundation.
Pine Bluff sits where the Arkansas Delta meets the Timberlands, and much of the ground here is clay that swells when wet and shrinks when dry. When a drain line leaks under a slab, that soil movement can crack the floor and shift the foundation, which is why we take slab leak signs seriously.
How the Test Works
Plug the line
We place a test ball or inflatable plug in the main line at the cleanout, sealing off the drains inside the house.
Fill with water
The drain system is filled to a set level, usually up to the lowest fixture or a marked point in the cleanout.
Watch and measure
We hold the water for a set time and measure any drop. A steady level passes. A falling level means a leak.
Isolate the leak
If it fails, we test sections of the system separately and use the camera to narrow down where the water is escaping.
Pressure Test vs. Camera vs. Smoke Test
| Test | Answers |
|---|---|
| Pressure (water) test | Is the system leaking? Pass or fail. |
| Camera inspection | What does the pipe look like inside, and where is the damage? |
| Smoke test | Where is sewer gas escaping into the house or yard? |
Signs Your Drain Line May Be Leaking Under the House
Slab leaks on the drain side are sneaky because they do not run up your water bill the way a supply leak does. The waste water simply soaks into the ground under the house. Watch for:
- New cracks in tile, concrete or drywall, especially near bathrooms or the kitchen.
- Doors that start sticking or will not latch like they used to.
- A musty or sewer smell that gets worse after showers or laundry.
- Carpet or flooring that feels damp with no obvious source.
- Slow drains in one area of the house while the rest drain normally.
None of these prove a leak on their own, which is why the test is worth doing before anyone opens a floor.
What the Result Means
Pass: the drain system holds water, so a leak under the slab is unlikely and the cause of your symptoms is elsewhere. You get the result in writing, which is useful for a home sale or a foundation company.
Fail: water is escaping somewhere. We then narrow it down section by section so any repair targets the leak and nothing more.
If the Test Fails
A failed test does not automatically mean tearing up your floors. Once we know which section is leaking, the options include tunneling under the slab from outside, cutting a small section of floor, or rerouting the line. Our under-slab sewer repair page explains each approach. For leaks in the yard, a leaking sewer line repair is usually a smaller job. You get the price before any work begins, the same way we handle every sewer line repair in Pine Bluff.
Call and my crew will test the drain lines, show you the result and give you the price for any repair before we start. Licensed and insured, 24/7.
Sewer Pressure Testing FAQ
How long does a sewer pressure test take?
Usually two to four hours, depending on how many sections need testing if the first test fails.
Can a pressure test damage old pipes?
Drain line tests use low water pressure, similar to a full drain system. They reveal leaks that already exist rather than causing new ones.
Is this the same as a water supply leak test?
No. A supply leak test checks the pressurized water pipes. This test checks the drain and sewer lines that carry waste out of the house.
Should I test before buying a house on a slab?
It is worth considering, especially for older slab homes. Pair it with a pre-purchase sewer inspection for the full picture.