The foundation company had done its job: a dozen piers, the slab lifted back toward level, doors closing like they hadn't in years. For most homeowners, that feels like the finish line. For the plumbing under the house, it's the moment of maximum stress — and that's exactly why we were there.
When a slab comes up, everything attached to it moves. Rigid drain lines that spent decades settled into one position get pulled, flexed, and re-seated in an afternoon. Most survive it. Some don't. The only way to know which kind of house you have is to re-test — which is why the post-lift hydrostatic test is written into the process for foundation companies we work with across DFW.
The re-test
Same procedure as a pre-test: seal the system at the outdoor two-way cleanout, fill the drain lines with water, and watch the level. On this Plano home, we'd tested before the lift and everything held. After the lift, it didn't — the level fell, slowly but unmistakably. The lift had opened a joint somewhere in the system.
Isolation testing narrowed it to one connection stressed by the movement — a joint, not a collapsed line, which is typical for lift damage. Caught now, it was a contained repair. Caught two years from now, it would have been a saturated slab, and very possibly new foundation movement undoing the repair the homeowners had just paid for.
The fix and the paperwork
We repaired the joint, re-ran the full test, and watched the level hold steady. Then we documented everything: pre-test results, post-test results, the repair between them, all dated — one copy to the homeowner, one to the foundation company. That paper trail matters more than people expect. It's the difference between "we think it's fine" and proof, and it's what keeps a foundation warranty conversation simple if anything ever comes up.
What Plano homeowners should know
If you're having foundation work done, the test after the lift is not optional fine print — it's how lift damage gets caught while it's still the easy kind of problem. Ask your foundation company who's doing the post-test and whether the results will be documented. If the answer is vague, that's worth fixing before the crew leaves.
Questions Plano homeowners ask
Why test the plumbing after foundation repair?
Lifting a slab moves every line attached to it. A post-lift hydrostatic test is the only way to confirm the drains survived the movement — and to document it.
What happens if a line fails the post-test?
We isolate the system to pinpoint the failure, repair that section, and re-test until it holds. Failures caught at this stage are usually joints, not whole lines.
Does the foundation company arrange this, or do I?
Either. Many DFW foundation companies bring us in directly; homeowners can also schedule the test themselves. What matters is that it happens — and gets documented.