(Residual/Pressure Head): The minimum pressure required at the furthest fixture (e.g., 20–30 PSI for a shower). Building Your Excel Spreadsheet

If the Excel sheet gives a very different result, check formula links and unit consistency.

The residual pressure required at the furthest fixture (e.g., 20 PSI for a shower) or the pressure needed to enter a pressurized main. 2. Determine Required Flow Rate (GPM) Before calculating head, you need to know the flow rate (