How do I Repressurise my boiler after bleeding radiators?

Filling the system after bleeding radiators.

Turn your heating and boiler off before you bleed the system.
Whenever you bleed radiators on a sealed system you should bleed one radiator at a time and repressurise as you go.
The air removed from your radiators will cause the system pressure to drop.

Why is my boiler not building pressure?

A boiler that keeps losing pressure is therefore always cause for concern. There are two main problems that typically cause a loss of pressure – water escaping somewhere in the system or a failure of the expansion valve and resulting damage to the pressure relief valve.

Should my boiler pressure increase when heating is on?

When you turn the heating on the water in the pipes and radiators heats up and expands. Your boiler pressure should not increase by more than 1 bar above it’s optimal working pressure when you turn the heating on.

What happens if you have no pressure in your boiler?

If your boiler pressure drops below the minimum safe pressure, your boiler and central heating will not function efficiently. It will instead spend more energy trying to heat your house with low pressure. Low boiler pressure will not necessarily damage your boiler or central heating system.

Why is one of my radiators not working?

If just one (or a few) of your radiators aren’t heating up, the most common reason for this is trapped air. If you’ve just turned the heating back on after the summer, air can become trapped in your radiators, causing them to be warm at the bottom but cold at the top. Your radiator should soon be nice and warm.

What should I do if my radiators bleed in my boiler?

Once you’ve bled the radiators, check the pressure gauge on your boiler. If the pressure is too low you’ll need to repressurise the boiler. If the system pressure is adequate, you can switch your heating on and check your radiators again to ensure that there are no remaining cold spots on the panels.

Why is the pressure on my boiler gauge so low?

Even in a very large building, the total system pressure drop might be as low as 1 psi. Your boiler gauge might not be accurate enough to measure such a low pressure. You’re not using the right gauge. The gauges that come with modern steam boilers have a tough time sensing steam when it’s at a very low pressure.

What to do if radiator pressure is too low?

If the pressure is too low you’ll need to repressurise the boiler. If the system pressure is adequate, you can switch your heating on and check your radiators again to ensure that there are no remaining cold spots on the panels.

Can a vented central heating system have a pressure gauge?

Heat only (or regular) boilers installed on a pressurised system will have a pressure gauge installed in the pipework. Open vented central heating systems (you will have feed and expansion tanks in the loft) are not pressurised and will not have a pressure gauge. What should the water pressure be?

Is it OK to bleed a radiator when water pressure is high?

Yes, if the problem is the air and water ratio inside of the system. If the problem causing the pressure to rise is something else, then bleeding won’t achieve anything. To bleed a radiator helps release the air out of the system and bring the water’s flow back on track.

Why does my boiler not have a pressure gauge?

Your boiler is a heat only boiler, not a combi, so it may have a small feed and expansion tank in the loft to top up system water, rather than being a sealed system. 2. If there is no small (20 litre or thereabouts) tank in the loft, it will have an expansion vessel somewhere, which is likely to have the pressure gauge close by.