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Plumbing Rough In Dimensions

Where to Cut Holes for Bathroom Sink, Toilet, and Tub

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Plumbing seems to really be all about the rough-in. The last step of connecting the sink, toilet, or tub feels almost superfluous.

That's why the rough-in--the placement of supply and drain pipes in your bathroom--is so important. Get the rough-in right and the rest is downhill.

When we speak of dimensions, we are referring to on-center. So, if two pipes are ten inches apart, we are measuring from the center points of each pipe, not the edges. Also base floor height is considered to be the subfloor (in new construction) or finish floor (in remodeling). Finally, the term "centerline" is an imaginary vertical line drawn through a key reference point (usually the drain pipe).

None of these dimensions are set in stone. Consider them general guidelines. They will vary according to your own bathroom. Consult the instructions that come with the fixture (sink, tub, etc.) for more precise dimensions.

Sink Rough-In Dimensions

  • Drain Pipe: About 16-20 inches above floor. We will consider the drain pipe to be a vertical centerline.
  • Supply Lines: Two holes. One hole is 4 inches to the right of centerline, another hole is 4 inches to the left of centerline Vertically, both holes are about 2-3 inches above the drain pipe.
  • Placement of Sink: Vertically, the sink should be about 31 inches above the floor. Measure up to the rim of the sink.

Toilet Rough-In Dimensions

  • Supply Line: One hole, between 5-10" above the floor. Off-set this supply line from centerline by five inches.
  • Discharge Hole: Off-set this hole from the wall framing by 12 1/2". Consider this hole to be centerline.

Tub Rough-In Dimensions

  • Shower Stub: 80". This is the highest point, the place where the shower nozzle will go. We will consider this centerline.
  • Tub Spout/Stub: 26"-35" high. Place this on the centerline.
  • Faucets: 10" above tub spout. Place one faucet 4" to the left of centerline and the other faucet 4" to the right of centerline.
  • Drain: Place drain on centerline. Total opening for drain access can be between 10"-14" off-set from framing, and 6"-8" wide.
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