How to Top Up My Boiler Pressure ? 

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We receive a lot of emails regarding boiler pressure being too low, below is an article on how you can easily top up your boiler pressure.

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What is boiler pressure and why does it matter?

The pressure shown on your boiler is determined by the volume of water in your heating system. It’s essential to get this right to ensure your heating system runs correctly and that components are not put under undue strain resulting in premature failure.

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What pressure should my boiler be at?

Combination boilers usually have a pressure gauge built into the appliance itself to indicate the pressure within the heating system. As a general rule, heating systems should run at a pressure of around 1 bar (when cold). It’s normal for this pressure to increase slightly when the system gets hot, but if the pressure in your heating system is over 2.5 bar, you may already have a fault, or a fault might be developing.

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When should I top up the pressure in my boiler?

The pressure should be checked periodically, checking it a few times a year is usually sufficient but there is no harm in checking it more often. When the pressure in a heating system falls below 1 bar, it needs to be topped up. This is done using a filling loop. Filling loops come in various designs but the most common is called a conventional filling loop that could be attached to your boiler. Please see the image below to see what a filling loop looks like.

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If you can not see something that looks like a filling loop on or around your boiler ? Some filling loops on modern combination boilers are often built into the appliance, in which case you’ll need to consult the manual, the appliance manufacturer or contact us to check how the system can be re-filled.

 

Step-by-step: topping up boiler pressure

When using a conventional filling loop (pictured below) to top up your boiler you must first ensure that the system is cold and the boiler is turned off. You can then add water (and therefore pressure) by turning the lever(s) or flat headed screws (this depends on the design of the loop itself) located at either end of the flexible braided hose. The levers or screws should be turned individually. They will likely only turn a quarter of a rotation from the off to on position, and you should observe the pressure gauge while you are turning each one.

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Slowly allow water into the heating system until the pressure gauge on your boiler reaches 1 bar. The lever/s (or screws) should then both be turned fully off again to prevent the system pressure from getting too high.

 

Once the system pressure is at 1 bar, bleed the radiators throughout the system and top up again as necessary (you might need to do this process multiple times). Once air has been removed from all the radiators and the system pressure is at 1 bar, the boiler can be turned back on and normal operation resumed.

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How often should I top up my boiler pressure?

It’s worth noting that although it is normal to top up a heating system a few times per year (four or five is reasonable), if you find that you’re having to do this on a regular basis, it may indicate a leak in the system or a fault with you boiler. If this is the case, contact your service engineer to investigate the cause of the issue.

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How To Bleed a Radiator ? 

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Over time, air trapped within a heating system can accumulate at certain points within the heating circuit. Most commonly, air will accumulate at the highest points in the system. This is often at the top of radiators or towel rails on the top floor of your home or building. This accumulation of air will stop your heating system from working as effectively as it should be.

 

When should I bleed a radiator?

A good indicator that an air pocket has accumulated in a radiator or towel rail is that it will be hot at the bottom and cold at the top. If you find your home isn’t warming up as expected, check all the radiators in your home are hot from top to bottom. If you find one or two that seem cooler at the top, it’s probably time to bleed the radiator.

 

Step-by-step: how do I bleed a radiator?

To remove air from a conventional radiator you’ll usually need a radiator bleed key and an old towel or handful of tissue paper or kitchen roll. First, identify where air pockets may have built up by feeling how hot each radiator is when the heating is on. Take note of where this is, then turn the boiler off and leave them all to cool. 

 

Once the system is cool, use the bleed / radiator key to turn the square screw in the centre of the bleed valve located at the highest point of one end of the towel rail or radiator. 

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The screw should not be fully removed but can just be turned clockwise in quarter turn increments until air can be heard releasing from the radiator.

 

Once air is heard, have your towel or tissue at the ready to catch any drips of water that are released. Once a steady stream of air-free water is being released from the vent point, the bleed key can then be used again to close the screw by turning it anti-clockwise.

 

This process will need to be repeated on all radiators where a build-up of air is suspected. On sealed systems, it will also be necessary to top up pressure in your system from time to time to allow all air to be removed (see above a guide to top up pressure in your boiler) Once all air has been removed, ensure the system is topped up (if necessary) and switch on the boiler.

 

How often should I bleed my radiator?

It is worth noting that although bleeding radiators is normal, this should only need to be done a few times a year. If you find that air is accumulating on a regular basis or at lower points in the system, you should contact us to let us know.

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