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Kitchen Remodel Cost Calculator

Drain relocation

Can the sink actually move, and what happens to the budget if it cannot

Of every decision in a kitchen remodel, this is the one that most often turns a predictable job into an open-ended one. Moving a sink is not moving a faucet. The waste line has to fall continuously all the way to where it meets the existing stack, and a floor only has so much depth to give it.

Can the drain physically get there

The move
ft

Set this to what your jurisdiction enforces. We deliberately do not preset a code value — see the note below the result.

The floor structure
in

A two-by-eight is 7.25, a two-by-ten is 9.25, a two-by-twelve is 11.25. Engineered joists vary; read the label on the web.

in
in

Sleepers, a mud bed, or a raised subfloor all add room here. A bare subfloor adds almost none.

What else moves with it

Derived feasibility

Not inside this floor

The drain needs 5.13 inches of vertical room and the floor offers 4.58. It is short by 0.54 inches, so this move cannot be made inside the existing floor at 0.25 inch per foot.

Fall the move requires 2.75 in distance times your slope
Total depth needed 5.13 in fall plus pipe diameter
Depth the floor offers 4.58 in
Margin -0.54 in
Furthest it can travel 8.8 ft inside this floor, at this slope
Usable joist depth 3.08 in

Trades this move brings in Plumber

  • At this slope the furthest the trap can travel inside the floor is about 8.8 feet. Shortening the move to that distance is usually cheaper than every alternative below.
  • The alternatives are a dropped soffit under the ceiling below, sistered or engineered joists, or a sewage ejector. All three are larger jobs than the sink.
  • The vent has to move with the fixture. Re-venting is what turns a one-day plumbing item into a three-day one, because the vent has to reach a stack or the roof and it has its own routing rules.
  • Running across the joists means boring every joist in the path. Each bore has to sit inside the safe zone, which is why only a fraction of the joist depth counts as usable here.

The arithmetic, in full

  1. Required fall. The trap moves 11 feet and the line must drop 0.25 inches for every foot it travels, so it needs 2.75 inches of vertical drop end to end.
  2. Depth the pipe occupies. Add the outside diameter of the pipe and its fittings, 2.375 inches, giving 5.13 inches of vertical space the floor has to contain.
  3. Depth the floor offers. Running across joists, only part of each joist depth is available, because a bore has to stay away from the top and bottom edges. That gives 3.08 inches, plus 1.50 inches of build-up above the joists, for 4.58 inches.
  4. The margin. 4.58 minus 5.13 is -0.54 inches. Positive means it fits. Negative means the move, at this slope, does not happen inside this floor.
  5. The useful inversion. Rearranged, the furthest the trap can travel and still fit is 8.8 feet. That number is worth more than the verdict, because it tells you where to put the sink instead.

What actually costs money when the answer is no

Opening a ceiling below

If the room underneath is finished, the drain route runs through somebody's living room ceiling. The plumbing itself might be a day. The ceiling repair, the texture match, the paint and the fact that the room has to be emptied are all separate line items in a room that was never part of the remodel.

Cutting a slab

On grade there is no cavity at all, so the line goes below the concrete. That means saw-cutting a trench the length of the run, breaking out and removing the spoil, laying and inspecting the new line while the trench is open, then filling, patching and levelling before any floor goes down. It is a specialist sequence with its own inspection hold in the middle of the schedule.

A sewage ejector

Where gravity genuinely cannot be achieved, a pump can move waste uphill. It solves the geometry and introduces a mechanical device with a service life, a power requirement and a failure mode under a kitchen floor. It is a real option and it should be a last one.

Or: move the sink less far

The cheapest fix is almost always to shorten the move. At 8.8 feet or less this drain stays inside the existing floor and the entire category of work above disappears. A sink two feet from where you wanted it, in a kitchen that came in on budget, is a trade most people would take if anyone had put it to them before demolition.

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