How to Fix Your Boiler Losing Pressure


Your boiler is an essential part of your home. It gives you heat and hot water. Therefore it’s important to keep it in good shape with regular maintenance. If your boiler is not working properly or to its full potential, there are a number of issues which may be causing this. One of them might be a problem with the boiler losing pressure. So, how do you fix your boiler losing pressure?

If you have noticed that your heating system has become less efficient or your pressure gauge has dropped to red, you need to top up the boiler pressure. In this article, we’ll find out more about what to do if you identify that your boiler is losing pressure.

What is Boiler Pressure?

Boiler pressure refers to the pressure of hot water running in your sealed central heating system. In comparison, water pressure is the pressure of the water coming through your taps.

Primarily, with your boiler losing pressure, it can lead to problems with heating your home efficiently. Additionally, it will also increase your energy bills because the boiler is working harder to heat up.

The first thing to do is to check your pressure gauge. This is on the boiler itself and will be in one of two forms. An analogue display includes a pointer and looks like a clock face or speedometer. The needle points to the pressure. Alternatively, your boiler will have a digital display and may show other information such as timers or temperatures. With a digital display, you may have to press a button to scroll through different measurements until you reach the pressure indicator.

You can check your boiler manual for details if in doubt.

Why is Boiler Pressure Important?

The ideal water pressure inside a boiler system should be between 1 and 1.3 bar. But it’s a good idea to check your boiler manual for the optimum range.

Low boiler pressure is nothing to worry about and it’s not likely to cause any damage to your boiler. However, it can have a large effect on the efficiency of your heating system. Essentially, with your boiler losing pressure, it will make it harder to heat your home.

High boiler pressure is more serious. If you have checked your pressure gauge and identified high pressure, the next step is to reduce it. There are a few ways to do this. You could try bleeding your radiators or opening the filter valve. If you can’t reduce the pressure, it’s very important that you call a gas safety engineer as soon as possible.

However, in this article we’re looking at what to do if your boiler loses pressure. Topping up your boiler pressure is a simple fix and can be carried out without a heating engineer.

How to Repressurise Your Boiler

The first thing to do is to identify what sort of filling system you have and then follow the instructions.

At some point during the boiler’s life cycle, you’ll have to top it up with mains cold water. You may notice this because the heating becomes less efficient or the pressure gauge turns to red.

There are two main ways of topping up the boiler. Either through an external filling loop or an internal filling loop.

External Filling Loop

You can identify an external filling loop because there are two valves. One is from the mains cold water and the second valve is connected to the heating system. You will also see a small hose. The hose allows the cold water to enter the heating system.

Firstly, attach the hose to each side of the valve and open the mains cold tap. Secondly, open the second tap which allows water in to the heating system. Next, watch the pressure rise and stop once the bar reaches just about one. Then, turn off both taps. Finally, take the taps off the hose.

Internal Filling Loop (with key)

If your boiler system has an internal filling loop with a key, you will usually find it on a flap underneath the boiler.

Firstly, you’ll notice an open black port on the front right hand side of the boiler. This is where the key fits. There should be a picture of an open padlock and a closed padlock. On the white key there is an arrow on the shaft. Align the arrow with the open padlock as you push It up into the open port.

Secondly, turn the key and watch the pressure rise to just over one bar. Next, turn the key back to the open padlock and remove.

Finally, you may have what’s known as a ‘keyless’ internal filling loop. If this is the case, you’ll see a blue lever at the bottom of your boiler. To repressurise the system with a keyless filling, simply pull down the blue lever. Once the pressure has increased to over one bar, release the lever.

Are you Still Losing Boiler Pressure?

If you have tried these methods and your boiler is still losing pressure, then there could be a number of reasons.

Perhaps there is a leak somewhere in your system which may be tricky to spot. It could be anywhere through the pipework. Have a look and see if you can spot any water leaks particularly around the joints and bends of the pipes.

If your boiler is over 10 years old, it may be showing signs of wear and tear. As a result, with your boiler losing pressure continually, it might be time to consider a replacement.

Maybe you haven’t had the annual service for the boiler If not, it’s a good idea to book one now.

To Conclude: How to Fix Your Boiler Losing pressure

To sum up, in most cases, low boiler pressure is nothing to be concerned about. We hope this article has helped you to learn how to fix your boiler losing pressure from home.

If you have investigated the problem yourself and you still have concerns, you should always seek the advice of a registered Gas Safe engineer. At Greener Homes, we are a team of friendly and professional heating engineers. All our staff are Gas Safe registered and fully trained to work professionally and safely.

If your boiler is losing pressure and you can’t work out why, give us a call at Greener Homes to book one of our engineers.