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Plumbing

Water Pressure Calculator

Convert between pressure and head height, and work out pressure at a fixture after elevation and friction losses.

Your numbers

Result

Pressure at the fixture 45.3 PSI
Loss from elevation 8.7 PSI
Supply pressure as head 138.6 Feet of water
Margin above the fixture requirement 25.3 PSI
Pressure at the fixture is 45.3 PSI. 25.3 PSI above what it needs.

Pipe and drain sizing is governed by plumbing code (IPC/UPC or local equivalent) and must be designed and installed by a licensed plumber. This is an educational estimate, not a design. Static pressure should be measured at a hose bib with no flow. Dynamic pressure during flow is always lower.

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Questions

About this calculator

How much pressure is lost per floor?

About 0.433 PSI per foot of rise, so roughly 4–5 PSI per storey. A third-floor bathroom starts around 13 PSI down on the ground floor before any friction loss.

What is normal house water pressure?

Typically 40–60 PSI. Above about 80 most codes require a pressure-reducing valve, since high pressure damages fixtures and appliances.

The formula

1 PSI = 2.31 feet of head; elevation loss (PSI) = height × 0.433

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