Convert Feet of Water to Pounds per Square Inch
Convert Feet of Water (ftH₂O) to Pounds per Square Inch (psi) instantly and accurately.
Conversion Formula
psi = ftH₂O × 0.433527504
About Feet of Water
One foot of water column (ftH₂O) ≈ 2,989 Pa - the US customary equivalent of cmH₂O used in civil and hydraulic engineering. Municipal water supply systems are designed for 40-80 psi head ≈ 92-184 ft; fire suppression sprinkler systems require minimum 7 psi ≈ 16 ft. Well pump specifications, sump pump head ratings, irrigation mainline pressure, and drainage calculations all use feet of head. 1 ft of water = 12 in WC = 0.4335 psi ≈ 2,989 Pa.
About Pounds per Square Inch
One pound per square inch (psi) ≈ 6,894.76 Pa - the dominant pressure unit in US industry and consumer products. Car tyres: 32-36 psi; truck tyres 80-120 psi; bicycle road tyres 80-130 psi. Home water supply: 40-80 psi; residential maximum 80 psi per plumbing code. Compressed air tools: 90-150 psi. Steam autoclave sterilisation: 15-30 psi. The distinction between gauge (psig) and absolute (psia) pressure is critical: gauge pressure is relative to ambient; absolute = gauge + ~14.696 psi. 1 psi = 6,894.76 Pa.
Quick Reference Table
| Feet of Water (ftH₂O) | Pounds per Square Inch (psi) |
|---|---|
| 1 ftH₂O | 0.433528 psi |
| 2 ftH₂O | 0.867055 psi |
| 5 ftH₂O | 2.16764 psi |
| 10 ftH₂O | 4.33528 psi |
| 25 ftH₂O | 10.8382 psi |
| 50 ftH₂O | 21.6764 psi |
| 100 ftH₂O | 43.3528 psi |