Water Pressure Loss Calculator
Water pressure drops as it travels through pipes due to friction and elevation changes. This calculator estimates the pressure at your fixtures to verify it meets code minimums (8 PSI for most fixtures).
Enter Your Measurements
Results
How to Use This Calculator
- Enter the supply pressure at your water meter (check with your utility or a gauge).
- Enter total pipe run length from meter to the farthest fixture.
- Select pipe diameter.
- Enter the peak flow rate.
- Enter the elevation rise if the fixture is above the meter.
How Water Pressure Calculation Works
Pressure is lost to friction as water flows through pipe — smaller pipes and higher flow rates cause more friction. Elevation also costs pressure: every foot of rise loses 0.433 PSI due to gravity. This calculator uses a simplified Hazen-Williams approximation with a 15% fitting factor added to the friction loss. IPC requires minimum 8 PSI at most fixtures and recommends pressure between 40–80 PSI. A Pressure Reducing Valve (PRV) is required if supply pressure exceeds 80 PSI.
Formula
Friction loss (PSI/100ft) ≈ (4.52 × GPM^1.852) ÷ (C^1.852 × d^4.87) simplified. Elevation loss = 0.433 PSI per foot of rise. Add 15% for fittings.