"Water Pressure and Elevation Math" is lesson 8 of 8 in the Plumbing (C-36) Learning Hub. It opens with "Elevation Change IS Pressure Change" and works through 5 short steps, then a worked example you can check yourself against.
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The worked example in the course applies this lesson to a realistic job in 3 steps, moving through "Determine direction", "Calculate the pressure gain from elevation", and "Add the gain to the source pressure".
Water weighs something, and that weight creates pressure based purely on how tall the column of water is above the point you're measuring - not on the pipe's diameter, shape, or length. Every foot you go UP in elevation from a supply source, you lose pressure. Every foot you go DOWN, you gain it.
The standard conversion is 0.433 psi of pressure for every 1 foot of elevation change - this comes from the weight of water itself and is a fixed physical constant, the same on every job. Some references round this to 0.43, but 0.433 is the precise number to use in calculations.
If a fixture sits BELOW the water source (like a basement sink fed from a street main), it gains pressure - multiply the drop in elevation (feet) by 0.433 and ADD that to the source pressure. If a fixture sits ABOVE the source (like a top-floor bathroom fed from a ground-level meter), it loses pressure - multiply the rise in elevation by 0.433 and SUBTRACT it from the source pressure.
The remaining 2 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.
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