Flow rate guide

As so many factors affect the required flow rate, professional confirmation is necessary. To calculate the likely peak demand, the table below shows actual flow requirements for each appliance and the likely simultaneous demand in low usage applications, normal domestic situations and higher usage. A suggested design flow rate can be established by multiplying the number of appliances by the flow figure in the relevant column.

It is important to note that there are instances where a different column must be used for a particular appliance. A sports club, for example, may need all of the showers running at once, so the figure used would be the actual flow requirement multiplied by the number of showers installed.

Low usage

Low usage

Care home for elderly persons, offices.

Domestic usage

Domestic usage

Individual private residences, infant schools.

Commercial usage

Commercial usage

Hotels, student accommodation, apartments.

Calculating flow rate design duty

Number of
appliances
X
Flow figure
(low/domestic/commercial)
=
Flow rate
design duty

The table below is intended as a guide to assist in the process of specifying a booster set

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Quantity Appliance Actual flow
requirement
(l/s)
Low
frequency
usage (l/s)
Domestic
frequency
usage (l/s)
Commercial
frequency
usage (l/s)
Peak flow rate
design duty
(l/s)
Basin (H&C) 0.15 0.005 0.008 0.017
Sink (H&C) 0.20 0.010 0.020 0.040
Bath (H&C) 0.30 0.020 0.030 0.070
WC 0.10 0.005 0.010 0.020
Shower (standard) 0.15 0.010 0.020 0.030
Shower (high flow) 0.50 0.040 0.065 0.030
Urinal 0.01 0.003 0.003 0.005
Bidet 0.08 0.002 0.003 0.004
Cleaner’s sink (H&C) 0.30 0.003 0.005 0.006
Domestic washing machine 0.20 0.007 0.008 0.010
Commercial washing machine 0.30 0.020 0.030 0.060
Total (l/s)

IMPORTANT NOTE: When calculating the pressure required, it is critical to allow for the static head and outlet pressure requirements in your calculations.

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