Recirculation Pump Sizing
Size hot water recirculation pumps for residential and commercial systems
Piping Information
Supply + return (or to furthest fixture for crossover)
Temperatures
Maximum temperature loss in loop (5-15°F typical)
Pump Requirements
Required Flow Rate
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Required Head
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Heat Loss
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Friction Loss
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Pipe Velocity
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Recommended Pump
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Note: For crossover systems, install thermal bypass valve at furthest fixture.
Heat Loss Formula
Q = U × A × ΔT
Q = Heat loss (BTU/hr)
U = Heat transfer coefficient
A = Pipe surface area (sq ft)
ΔT = Temp difference (°F)
GPM = Q / (500 × ΔTdrop)
Flow needed to offset heat loss
Typical Pump Sizes
| Application | GPM | Head (ft) |
|---|---|---|
| Small Residential | 0.5-2 | 2-6 |
| Large Residential | 2-5 | 4-10 |
| Small Commercial | 5-15 | 8-20 |
| Large Commercial | 15-50 | 15-40 |
Heat Loss Coefficients (BTU/hr per linear foot per °F)
| Pipe Size | Bare Copper | 1/2" Foam | 1" Foam | 1" Fiberglass |
|---|---|---|---|---|
| 1/2" | 0.55 | 0.18 | 0.12 | 0.10 |
| 3/4" | 0.68 | 0.22 | 0.14 | 0.12 |
| 1" | 0.82 | 0.26 | 0.17 | 0.14 |
| 1-1/4" | 0.98 | 0.30 | 0.19 | 0.16 |
| 1-1/2" | 1.12 | 0.34 | 0.22 | 0.18 |