Central Heating Boiler With Low Pressure

Boiler Pressure Gauge

Re-pressurising a boiler with a central heating filling loop

Modern gas boilers rely on having the correct pressure level in the system. A common problem that plumbing and heating engineers are called out to deal with, but one that you can fix yourself if you have the confidence, is a drop in pressure.

If the pressure drops below a certain level the boiler won’t fire up, or it will fire up for a short period and then shut off. Either way you’ll be left with no heating and no hot water.

The boiler will probably show an error code on a display panel or a by pattern of lights. Look this up in your boiler manual to check that it is a pressure problem. There’s also a dial on the boiler showing the pressure, with the correct level indicated by numbers or a green band.

If your boiler has a central heating filling loop, also known as a refill pressure loop, you can re-pressurise the system yourself, but take care to avoid water spillages. It is best to do this with the heating system cold as well.

The loop is a flexible metal hose below the boiler and it’s usually only attached at one end – the water supply end. Some boilers have the loop permanently connected at both ends, in which case look for a metal flexible hose with a tap at one end.

Connect the free end to the connector on the boiler’s inlet pipe – this may have a cap on it which you remove first – and screw the connector on hand tight. Slowly open the lever by the connector to allow water into the system and watch the dial move into the correct position.

Most boilers require a pressure between 1.2 and 1.5 bar, but check your manual for the exact level. Once that’s done, slowly turn the tap back to close the water off. Disconnect the hose if it was detached when you started.

Get the experts in

If you find that you have to do this more than a couple of times a year, then it’s likely there’s a problem in the system that needs looking at.

If you are concerned about pressure drops, and are looking for plumbers, Aylesbury’s finest are here to help you. Call Shaw’s Plumbing and Heating on 0800 8 247 585 and we’ll be glad to help.

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