How could mains water pressure affect my combi oil boiler?

For all cold mains-fed combi boilers, it is important to ensure that the water main is large enough to deliver adequate water to the boiler while other cold outlets are in use (such as flushing toilets, washing machine filling or cold taps being run). If the water main is insufficient, cold water to the boiler will be reduced when more than one outlet is used. The chances of this happening could be reduced by giving the boiler priority over all the other outlets and this could be done by your installer piping the boiler up as the first draw off from the mains.

The performance of any mains fed hot water system depends on the mains water supply offering an adequate dynamic pressure and flow rate. This is because the flow rate must be sufficient to supply hot and cold water simultaneously.
Whilst there may be sufficient mains pressure, the flow rate is dependent on the size, type and condition of the incoming main. Please note - it is important not to confuse pressure with flow. Also, dynamic pressure will be less than the static pressure.

A water pressure reducing valve may also be required to protect the appliance from excessive incoming mains pressure. The maximum incoming water pressure is normally less than 8 bar. If you have any concerns regarding your water pressure, please contact your heating engineer.

Are you a professional? View our Professional Support Centre

Find an Installer

Search our network of heating engineers to find local installation and servicing companies in your area


Home Heating Blog

Discover more about home heating solutions, care and support with our informative blogs

Read more

Couldn't find what you were looking for?

Alternatively you can speak to a member of our team - Subject to Operating Times

Return to top