How a drain gets moved
- Find out what is in the slab. Post-tension or conventional, and where the existing drain line runs.
- Cut and trench. The concrete is saw-cut along the new path and removed, with dust control.
- Run the new pipe. It ties into the existing line and has to fall continuously toward it. The vent has to work for the new location too.
- Inspection. The inspector sees the pipe while the trench is still open.
- Backfill and patch. The trench is filled, compacted and the concrete is poured back before the floor goes down.
Toilet versus shower drain
| Toilet | Shower | |
|---|---|---|
| Pipe size | Larger drain line | 2-inch drain |
| Difficulty | Harder. Bigger pipe, more trench, and slope limits how far it can go | Easier, especially over short distances |
| Common move | A few feet along the same wall | Center to one end, or to a linear drain |
Distance is what matters most. Drain pipe has to slope the whole way, so the farther the fixture moves from the existing line, the deeper the pipe ends up. At some point the run stops working and the layout has to change.
Post-tension slabs
Many Valley homes built after the mid-1990s, especially in the East and West Valley, have post-tension slabs with steel cables under tension in the concrete. Look for a warning stamp in the garage floor. The cables must be located before any cut, and the trench has to be planned around them. Sometimes a cable sits exactly where the pipe needs to go, and the plan has to shift. That is a conversation to have before the contract, not after demo.
Permits and older homes
Moving a drain is a plumbing change, so it needs a permit in Phoenix and the surrounding cities. Confirm the details with your city. In older homes the drain lines under the slab may be cast iron, and they are sometimes worn. If we open the floor and find a bad section, we show you photos and replace it while the trench is open.
Is it worth it?
Often yes. Moving a toilet a few feet can turn a cramped bathroom into one that works. But it adds cost and days, so we always price the layout both ways. Layout changes are part of our upper full remodel and primary bathroom packages, which run $18,500 to $60,000 and $32,000 to $95,000.
Key facts
- Possible on a slab?
- Yes, by trenching the concrete
- Permit
- Plumbing permit required; confirm with your city
- Shower drain size
- 2 inch
- Post-tension slab
- Locate cables before any cut
Related questions
Where we do this work
Services: Full Bathroom Remodel · Master Bathroom Remodel
Bathroom remodeling in Chandler, Peoria, Tempe, and across the Valley.