Raising a slab moves everything cast into it, including drain lines that have been sitting in their settled position for years. A plumbing test after the lift is the way that gets caught, and it is worth agreeing to before the work.

The reason a Phoenix leak test is worth doing first

Two things make the pre-test worth its cost here. The median house dates from 1984, old enough that the original drain material is worth establishing before anything is lifted, and across 642,867 housing units that material is not one thing. And a leak under a slab puts water into the ground directly beneath the house, so a leak can be the cause of the movement rather than a consequence of the repair, which only a test run before the lift can show.

The reasoning behind that

Drain lines under a slab have no flexibility to spare. They were installed level, the ground moved, and they have been sitting in the moved position long enough for the joints to accept it. Restoring the slab toward its original elevation asks those joints to move again. Sometimes the pipe was already compromised and the lift reveals it rather than causing it. That distinction matters commercially and it is almost impossible to settle after the fact, which is the argument for a pre-work test as well as a post-work one. A static or hydrostatic test isolates the drain system and holds water in it to see whether the level falls. Run before and after, the pair establishes what changed. Run only afterwards, it establishes a problem with no agreed starting point. Ask for both, in writing, as part of the scope. Any firm that has done this work before will expect the question and many will offer it unprompted.

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