New construction builder said to leave 8 inch by 13-14 jackhammered hole, made to reposition bathtub drain pipe in basement slab floor. Tub was set over to cover up hole. Bath walls and floor tiled. Builder said it is standard practice to leave large rectangular hole under bathtub.

This seems wrong. How large of a hole in a basement concrete slab floor, is too big? Is there a code violation in Colorado?

  • Doesn't sound right to me. I can see that before the true drain pipe location is established (may be tub & tub placement dependent), you may want allow some wiggle room for the final pipe placement. But once you know where the drain has to go to mate up to the tub, that's it.
    – SteveSh
    Sep 16, 2022 at 22:25

2 Answers 2


Bath traps are very common and an 8" by 4" wouldn't be considered large depending on the location of the main drain pipe that the tub drain has to be connected to and maintained. I would check with your local inspectors due to the possibility of flooding. I've seen bath traps in many basements but most of them have had sump pumps. Some have had a thin concrete layer poured over them that could be easily broken through for maintenance or filled in with gravel to impede insects. It might have been a good idea to check into this before the construction was completed. Hopefully, you've got some pictures.


This is typical on any tub which sits on a concrete slab. Bathtubs need to be hooked up under the floor level that they are sitting on. There needs to be a recess in the slab to allow for this hook up. It would also not be very wise to concrete this in after the tub is set and water tested as it would create a nightmare for whomever needed to replace this tub later on. The "filling of the hole" solutions given in the answer by @Jack seem much more appropriate.

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