Often, the hardest part about installing plumbing in a bathroom is the rough-in stage. There are generally accepted plumbing rough-in measurements for sinks, toilets, bathtubs, and showers. In addition, fixture manufacturers typically provide rough-in specifications in their product literature. Check the standard dimensions against the manufacturer's specs to make sure they will work for your installation. Learn more about the bathroom plumbing rough-in phase below.
What Is a Bathroom Plumbing Rough-In?
A bathroom plumbing rough-in is the phase of measuring and marking fixture centerlines and heights, drains, and clearances. During this stage, a plumber excavates, lays, and routes water and drain lines from the utility to your home's wall cavities. The water lines and drain lines are then connected to the main water supply valve and sewer or septic system. Finally, vent stacks are run to the roof.
Common Bathroom Rough-In Dimensions
| Toilet | Sink | Shower/Tub | |
| Supply Line (Vertical) | 8 1/4" | 2" to 3" higher than drain pipe | 80" shower; 20 to 22" tub; spout 4" above tub rim |
| Supply Line (Horizontal) | 6" max from center | 4" to left and right of center | 8" apart |
| Discharge/Drain Hole from Back Wall | 12 1/2" | N/A | 14" |
| Discharge/Drain Hole (Vertical) | 0" | 16" to 20" | 0" |
| Fixture (Side to Side Buffer) | 15" to 18" min | 15" to 20" min | 18" min |
| Fixture (Front Buffer) | 21" min | 21" min | 18" min |
Toilet Rough-In Plumbing Dimensions
Here are standard rough-in dimensions for a new toilet:
- Toilet supply line (height): Ideally, 8 1/4 inches above floor; generally, between 5 and 10 inches above floor
- Toilet supply line (horizontal): Hole should be 6 inches to the side of the centerline; check the toilet to confirm the water supply connection location
- Toilet discharge hole from back wall: Offset hole from back wall by 12 1/2 inches
- Toilet discharge hole (vertical): Drain located at floor height; distance is zero
- Toilet side-to-side buffer: Measured from the center of the toilet to either side, minimum clearance is 15 inches to any wall or other fixture; 18 inches recommended
- Toilet front buffer: Measured from the front rim of the toilet forward, minimum clearance is 21 inches to the nearest obstruction; 30 inches recommended
The Spruce / Madelyn Goodnight
Bathroom Sink Rough-In Plumbing Dimensions
Here are standard rough-in dimensions for a bathroom sink:
- Sink supply line (height): Two vertical holes about 2 to 3 inches above the drain pipe
- Sink supply lines (horizontal): Two holes for hot and cold water, each 4 inches from the centerline on the left and right sides
- Sink discharge hole (vertical): About 16 to 20 inches above the floor, with the drain pipe as the vertical centerline
- Sink side-to-side buffer: From centerline, 15 inches minimum, 20 inches recommended
- Sink front buffer: Minimum distance to nearest obstruction is 21 inches, 30 inches recommended
- Placement of sink: Vertically about 31 inches above the floor, measured from the top of the base floor to the rim of the sink
The Spruce / Madelyn Goodnight
Shower and Bathtub Bathroom Rough-In Dimensions
Here are the standard rough-in dimensions for a shower and bathtub:
- Shower supply (vertical): Shower arm 80 inches from floor; shower head about 65 to 78 inches above floor
- Tub supply (vertical): Faucet valves 20 to 22 inches above the floor
- Faucets: 4 inches to the right/left of the centerline
- Tub spout: 4 inches above the tub rim
- Drain: On the centerline
- Discharge hole from back wall: Opening for drain access between 10 and 14 inches offset from framing, and 6 to 8 inches wide
- Discharge hole (vertical): Drain located at floor height; distance is zero
- Fixture (side to side buffer): 18 inches minimum required buffer
- Fixture (front buffer): 18 inches minimum required buffer
The Spruce / Madelyn Goodnight
Tips for Bathroom Plumbing Rough-Ins
Make sure your bathroom renovation is off to a good start with these tips for plumbing rough-ins:
- Choose your fixtures first for the most accurate rough-in.
- Strategically adapt existing plumbing even for new fixtures.
- Triple-check connections and measurements for your rough-in.
- Get all the required plumbing permits for a plumbing rough-in before you begin.
- All dimensions must be cross-checked against the local code as the final authority.
- What's included in bathroom plumbing rough-ins?
A bathroom plumbing rough-in includes vents, drain lines, sewage systems, and running water supply lines.
Do shower drains need vents?Yes, shower drains need vents to prevent poor drainage issues.
Does the hot water line go on the left or right of a plumbing fixture?In the United States, the hot water line is typically placed on the left side of a plumbing fixture.
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