Most foundation movement in McKinney is caused by clay soil doing what clay soil does. But some of it is caused by a broken pipe quietly soaking the ground under your slab, and those two situations call for very different responses.

Installing piers without checking is how people end up paying twice.

What the test is

A plumber isolates your drain system — usually by pulling a toilet and setting an inflatable test ball at the cleanout — then fills the lines with water to a defined level and watches whether that level drops.

Water doesn’t leave a sealed system on its own. If the level falls, something below the slab is leaking. Simple test, unambiguous result.

If it fails, the next step is isolation: sectioning the system to narrow down where, then camera work to see the break. In McKinney expect $250 to $500 for the initial test and $400 to $900 if isolation and camera inspection are needed. Some plumbers roll the test into a service call.

Note that a standard hydrostatic test covers drain and sewer lines — the ones under the slab flowing away from the house. Pressurized supply lines are tested differently. Ask for both if you have reason to suspect either.

Why it matters before you pier

1. Piers don’t stop a leak

A cracked sewer line pours water into the soil continuously. Piers transfer load to deeper strata, which helps, but the leak keeps saturating soil around and between them, and unpiered sections keep moving. You’ve spent $12,000 and the house is still going.

2. It’s your one realistic shot at insurance

This is the big one. Texas homeowners policies exclude earth movement almost universally, so foundation damage from clay shrinkage is on you. But damage resulting from a sudden covered event — including plumbing leaks in many policies — can be a different story. Coverage varies enormously by carrier and policy form, and some cover the resulting damage while excluding the pipe repair itself.

You cannot make that claim without documentation that a leak existed. Repair the foundation first and the evidence is gone. Read your policy, or have your agent read it to you, before you spend anything.

3. It occasionally means you don’t need piers

Uncommon, but real. If a leak has been running for a year and the movement is recent and localized, fixing the pipe and letting soil moisture normalize sometimes brings a slab back most of the way on its own. Worth waiting a season to find out before committing to piers.

Signs you should test

• A water bill that climbed without explanation
• A warm spot on the floor, which points at a hot water supply line
• Soil at one spot along the foundation that stays damp when everything else is dry
• Movement concentrated near a bathroom, kitchen, or laundry rather than at a corner
• Slow drains, gurgling, or sewer odor
• Cast iron drain lines, standard in McKinney homes built before roughly 1975 and reaching the end of their service life now
• Mature trees close to the sewer lateral — roots find joints and open them

Honestly, test regardless. Against a $10,000 repair, a $350 test that rules out a variable is cheap certainty.

Use an independent plumber

Hire the plumber yourself rather than taking one arranged by the foundation contractor. Not because contractors are crooked, but because a test result that determines whether a $12,000 job happens shouldn’t come from someone with a stake in the answer. This applies to us too.

Ask for the written report and the camera footage. You’ll want both for an insurance claim, and a future buyer’s inspector will ask.

If it fails

Repair options are tunneling — digging a tunnel under the slab from outside, more expensive but leaves your floors alone — or breaking through the slab from inside, cheaper but destroys flooring and requires patching. Costs commonly run $4,000 to $15,000 depending on depth, distance, and method.

Fix the plumbing, then wait. Give the soil a season or two to normalize and re-run the elevation survey before deciding on piers. The picture frequently changes.

More on what repair costs here, or foundation repair in McKinney.