Drain Sizer
Adding or moving fixtures? Add what's on the line below and check the drain pipe can carry it at your slope.
Lavatory (bathroom sink)
1 DFU each
Bathtub
2 DFU each
Shower
2 DFU each
Shower (over 5.7 gpm)
3 DFU each
Kitchen sink
2 DFU each
Dishwasher
2 DFU each
Laundry tray
2 DFU each
Utility sink
2 DFU each
Clothes washer (residential)
2 DFU each
Clothes washer (commercial)
3 DFU each
Floor drain
2 DFU each
Dog wash station
2 DFU each
Toilet
3 DFU each
Total on this line
5 DFU
2in capacity
6 DFU
Approximate half-full flow at your slope: 13.8 gpm.
This pipe can carry it
5 of 6 DFU used. Leave some headroom for future fixtures if you can.
Drain tips that prevent callbacks
- 1Keep the slope consistent end to end — dips (bellies) collect water and solids and clog first.
- 2Put a cleanout at the upstream end of the run so the line can be snaked from the start.
- 3Tie a washing machine in downstream of other fixtures — its surge is the hardest hit the line takes.
- 4Use hair traps on pet-wash stations; fur is a top clog cause in drain lines.
- 5Vent every fixture. An air admittance valve (AAV) is an option — mount it at least 4 inches above the branch and keep it accessible for service.
Want a licensed pro to look at this?
Call or text DDJ Handyman at 850-333-8841.
VoltCheck provides diagnostic guidance only. It does not replace an inspection by a licensed electrician, plumber, or HVAC technician. When in doubt, turn off power at the breaker and call a professional.
