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How to fill a pressurised heating system

A quick guide to refilling a heating system

This guide will show you how to re-fill a pressurised heating system that has been drained down.

Follow the instructions or watch the video to discover the best way to fill a pressurised heating system.

How do I refill my heating system?

To begin with, you will have to close all of the air vents and drain offs by turning them clockwise.

Fill Pressurised Boiler_1_Close Vents

Before filling up it’s important to add central heating inhibitor.

Do this by simply removing a radiator blank and pouring the inhibitor into the system.

Fill Pressurised Boiler_1_Remove Air Vent
Fill Pressurised Boiler_3_Pour Inhibitor

Doing this will help to prevent corrosion throughout your heating system and reduce the chance of having heating problems in the future.

Follow the inhibitors manufacturing instructions; generally, one tub or bottle will be adequate for up to 10 radiators.

Where will I find my filling loop?

By your boiler, you should have a filling loop on the pipework.

Fill Pressurised Boiler_4_External Filling Loop

Or you may have an internal filling loop situated at the bottom of your boiler.

Fill Pressurised Boiler_5_Internal Filling Loop

To begin refilling your system, open the filling loop to the downstairs radiators first.

Fill Pressurised Boiler_6_Downstairs Bleed

Once you have done this, you can repeat the process for all of the upstairs radiators too.

Fill Pressurised Boiler_7_Upstairs Bleed

Turn your radiator key anti-clockwise until water begins to trickle out.

Fill Pressurised Boiler_8_Rad bleed to fill

Please note that if you have a towel radiator, be sure to do this last as it is normally the highest point of the heating system.

Fill Pressurised Boiler_9_Towel Rail bleed to fill

Once you have filled all of your radiators, close the filling loop ensuring that the system pressure is around 1-to-1.5 bar. It may help if someone monitors the pressure whilst you are filling up so you don’t over-pressurise the system.

Fill Pressurised Boiler_10_Boiler

After you have re-pressurised the system, you can then turn your boiler back on. Always make sure that all of your radiators are warming up.

And that’s it, you have (or should have) successfully filled your pressurised heating system!

Please note: Our ‘How-To’ manuals are intended only as a guide to assist you with common home heating tasks. Please do not attempt to undertake this task if any of the instructions are unclear, or if you are in any doubt about what to do. Instead, seek advice from a professional.

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