How could mains water pressure affect my combi oil boiler?

If your Grant Vortex Combi oil-fired boiler is cold mains fed, having the required water pressure and flow rate is crucial for the efficient operation of your boiler. The performance of a mains fed combi boiler is dependent on the cold mains water supply being able to provide sufficient pressure and flow rate to both the hot and cold water outlets simultaneously. The pressure of the incoming mains water feeding into your combi boiler should be between 2.5 and 8 bar and significant fluctuations above or below this range will impact your boiler’s performance.

How does low water pressure affect my boiler?

If your mains water supply pressure or flow rate is insufficient, the performance of your boiler will be reduced when more than one outlet is being used, such as running a washing machine or flushing a toilet at the same time as drawing hot and cold water from a tap. Before your installer fitted your combi boiler, they should have completed checks on the mains water pressure coming into your home to ensure that both the water pressure and flow rate were suitable for the installation and operation of a combi boiler. And, if required, your installer would have made modifications to the supply system as well as ensuring that the mains water connection to your boiler is the first connection from the mains supply. For a Grant Vortex Combi boiler, a minimum mains water inlet pressure should be between 2.5 and 3 bar.

How does high water pressure affect my boiler?

If your mains water pressure is too high, this could cause damage to your boiler and potentially the wider system. Excessive water pressure can lead to the failure of components and seals within the boiler if the boiler is not protected. In some situations, a pressure reducing valve may be required where the maximum allowable water pressure is exceeded – with a Grant combi boiler, if the mains water pressure is above 8 bar, a pressure reducing valve should be fitted. For a Grant Vortex Combi boiler, a maximum mains water inlet pressure should be between 8 bar.

Where can I check the pressure of the mains water?

To check the water pressure and flow rate of the mains water supply to your property, you will need to contact your installer. Your installer can check both the standing and operating mains water pressure to your property using a suitable gauge and they can use a suitable Weir gauge to the check the flow rate of water at outlets within the property, such as a tap.

If you have a sudden loss or increase in the pressure with your mains water supply or if you have any other concerns regarding your water pressure, please contact your heating engineer.

Left: An installer can check both the standing and operating mains water pressure to the property using a suitable gauge. Right: An installer can use a Weir gauge to check the flow rate at the outlets within the property.

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