Recirculating Pump Calculator
Size a hot water recirculating pump based on loop length, pipe diameter, and fixture count.
Results
Visualization
How It Works
A recirculating pump keeps hot water circulating through pipes so you get instant hot water at fixtures. It saves water (no waiting) but uses electricity. Timer or demand-activated pumps reduce energy cost.
The Formula
Total Head = (Loop Length x Friction Factor) + (Fittings x Equivalent Length)
Energy = Pump Watts x Hours/Day x 365 / 1000
Energy = Pump Watts x Hours/Day x 365 / 1000
Variables
- Head — Resistance the pump must overcome, in feet of head
- 0.05 — Approximate friction loss per foot for 3/4" copper
Worked Example
100 ft loop, 3/4" pipe, 4 fixtures: Head = 100 x 0.05 + 4 x 3 = 17 ft. Use 1/12 HP pump. ~$30/yr energy.
Practical Tips
- Timer-based operation (morning/evening only) cuts energy use by 60%
- Demand pumps activate on button press — zero standby energy
- Insulate the return line to reduce heat loss
- Dedicated return lines outperform crossover valve systems