Enter pipe size, material and flow rate to check velocity against AS/NZS 3500.1 limits and estimate pressure drop.
AS/NZS 3500.1 recommends a maximum flow velocity of 3 m/s for cold water and 2 m/s for hot water to prevent noise, erosion and water hammer. This calculator flags any velocity exceeding 3 m/s.
This calculator uses the Hazen-Williams formula to estimate friction pressure drop (kPa/100 m). Each pipe material has a different roughness coefficient (C-factor): PVC 140, copper 130, galvanised steel 100.
For 30 L/min (0.5 L/s) in copper pipe, DN25 gives a velocity of approximately 1.7 m/s — well within limits. DN20 would give 2.9 m/s which is borderline. Enter your exact values in the calculator above.