Pressure at Point
5.3 PSI
Elevation Loss
21.6 PSI
Friction Loss
33.1 PSI
Velocity
5.3 ft/s
5.3 PSI
21.6 PSI
33.1 PSI
5.3 ft/s
Critical (<20 PSI)
Ideal residential pressure: 40–60 PSI. Minimum recommended: 20 PSI.
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Inputs
Result
Elevation loss = 50 × 0.433 = 21.7 PSI. Friction loss through 200 ft of 3/4" copper at 8 GPM is approximately 4.8 PSI. Delivery = 60 - 21.7 - 4.8 = 33.6 PSI.
Inputs
Result
No elevation change. Friction loss through 100 ft of 1" PEX at 5 GPM is minimal at approximately 0.9 PSI. Delivery = 60 - 0 - 0.9 = 59.1 PSI.
Water pressure drops 0.433 PSI for every foot of elevation gain. A 100-foot elevation difference causes 43.3 PSI of pressure loss due to gravity alone.
| Elevation Gain | Pressure Loss | Typical Scenario |
|---|---|---|
| 10 ft | 4.3 PSI | One story up |
| 20 ft | 8.7 PSI | Two stories up |
| 50 ft | 21.7 PSI | Hilltop house from street |
| 100 ft | 43.3 PSI | Steep hillside property |
| 150 ft | 65.0 PSI | Mountain homes – booster needed |
The minimum recommended water pressure for residential use is 20 PSI, but most codes require 40 PSI at fixtures. Ideal residential pressure is 40-60 PSI.
| Pressure Range | Rating | Effect on Fixtures |
|---|---|---|
| Below 20 PSI | Too low | Toilets won’t fill, no shower flow |
| 20–40 PSI | Low | Weak showers, slow dishwasher fill |
| 40–60 PSI | Ideal | Good flow at all fixtures |
| 60–80 PSI | High | Works fine, consider a PRV |
| Above 80 PSI | Too high | Damages valves, causes leaks |
Smaller pipes create more friction, causing greater pressure loss. A 1/2" pipe loses significantly more pressure than a 3/4" pipe at the same flow rate. Upgrading pipe diameter reduces friction loss.
| Pipe Diameter | Friction Loss (10 GPM, 100 ft copper) | Relative |
|---|---|---|
| 1/2" | 38.2 PSI | 10× baseline |
| 3/4" | 3.8 PSI | Baseline |
| 1" | 0.9 PSI | 4× less |
| 1-1/4" | 0.3 PSI | 13× less |
PEX and PVC have the lowest friction loss with Hazen-Williams C values of 150. Copper has C=140, while old galvanized pipes have C=120, causing the most friction loss.
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Last Updated: Mar 26, 2026
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