Horsham Plumbing – Flow Rate Calculations

Flow Rates

The following is a list of typical flow rates from taps in a two storey house with a cold water storage tank in the loft and a hot water storage tank on the first floor.

Ground Floor Kitchen:  Cold tap is mains water approxiametly 20 litres/min, hot tap is 12 litres/min

First Floor Bathroom: Bath, hot and cold is 15 litres/min, basin hot and cold is 10 litres/min

These flow rates are based on 1/2″ and 3/4″ taps. A lot of the more modern taps will have reduced flow rates. Also a lot of modern taps are only suitable for high pressure systems.

Note  on Combi boilers:-

A 24kw combi will give 9 litres/min at 35’C temperature rise.

A 28kw combi will give 12 litres/min at 35’C temperature rise.

A 35kw combi will give 14 litres/min at 35’C temperature rise.


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Rusper Plumber – Flow rate guidance