DWS - Caleffi

Domestic Water Sizer


Thermostatic or electronic mixing valves are used in domestic hot water production systems in order to keep the mixed water sent to the user constantly at the temperature set whatever the supply pressure and temperature conditions or the flow rate drawn.

Pressure reducing valves are devices that, when installed on private mains water supplies, reduce and stabilise the pressure of the water coming in from the public mains supply which is, generally, too high and variable for correct use in domestic systems.


When designing a mains water supply the first requirement is to ensure that each drawing point delivers hot or cold water correctly. There are no specific standards or criteria on simultaneous use for sizing domestic water supply system components such as pressure reducing and mixing valves in particular. However, it is recommended that a simultaneous use coefficient is used for these devices as well in order to avoid over-sizing and ensure optimal operation.


To make calculations easier and ensure that they are accurate, Caleffi has developed a free Domestic Water Sizer application for sizing systems. It is available online at www.caleffi.com as well as webapp. 

DOWNLOAD IT NOW at App Store and Google Play.

In detail, mixing valves must be sized correctly to ensure that the water is mixed at the required temperature, precisely and safely. Pressure reducing valves must be sized to enable the system flow rate to be calculated and the pipe flow speed checked, to avoid noise and rapid wear of the delivery appliances.

The Caleffi sizer guides designers through the calculations and ensures that the results are accurate.