Estimate drain pipe flow rate, GPM capacity, drainage demand, pipe velocity, total fall, slope, and capacity margin for gravity drain lines, sewer drains, branch drains, floor drains, storm drains, and general drainage planning.
Pipe flow capacity:
The calculator estimates how much water a drain pipe can carry using pipe area, fill depth, slope, and estimated flow velocity.
Drain demand check:
The calculator estimates demand from known flow, DFU load, and stormwater runoff, then compares it to pipe capacity.
Flow velocity:
The calculator estimates flow velocity from slope and shows whether the drain may be slow, typical, or fast for planning.
Slope capacity check:
The calculator compares pipe capacity at the entered slope against the estimated drainage demand.
A drain flow calculator helps estimate whether a drain pipe has enough capacity for fixture drainage, sewer flow, floor drains, stormwater, yard drains, or gravity drainage lines.
It can help compare GPM capacity, DFU demand, stormwater runoff, pipe velocity, slope, total fall, pipe area, and capacity margin.
Your result shows estimated drain flow capacity, demand, velocity, and capacity margin. Use this as a planning estimate only. Drain and sewer systems should be sized according to local plumbing code, pipe material, venting, slope, cleanouts, fixture load, and the full drainage layout.
Drain flow is the amount of water or wastewater moving through a drain pipe over time. It is commonly shown in gallons per minute.
Pipe diameter, slope, fill depth, pipe material, fittings, venting, and the type of drainage all affect drain flow capacity.
This calculator uses a planning factor of GPM per DFU. Final DFU-to-flow relationships should be checked against code tables and design standards.
No. This calculator gives a planning estimate. Final drain sizing should follow local plumbing code and be verified for the actual system layout.