Why is my boiler losing pressure?

We frequently get asked what causes a central heating boiler to lose pressure. If you suddenly find yourself without any hot water or heating, the first thing you should do is check your water pressure. Looking at the pressure gauge on the front of your boiler, a normal reading would be anywhere between the 1 and 1.5 bar. Should the water pressure drop below this mark, the system will not produce any hot water and the boiler will need repressurising. It’s actually quite straightforward to repressurise a boiler. Please refer to your manufacturer’s instructions for guidance on how to do this safely or for a Worcester Bosch product, simply follow these handy instructions. If your boiler keeps losing pressure, even after repressurising, it’s likely your system has a more crucial problem and will need addressing by a professional heating engineer. Here are the two main causes of lost boiler pressure and how to identify them successfully.

Boiler leak

One typical reason why a boiler can lose pressure is a leak in the system. It could be a hidden pipe, a radiator valve or anything else that is causing water to leave the system. The quickest way to determine whether you have a leak or not is by checking all of the parts to your central heating system. This includes the pipework, the radiators and especially where different parts of your system are connected together. If proof of a leak isn’t so obvious, bear in mind it could also be happening in a place where you can’t see i.e. under the floorboards. Radiators can also produce leaks on their surface due to corrosion over time.

Faulty boiler valve

Another likely culprit that can cause a boiler to lose pressure is a faulty pressure relief valve or as it’s sometimes referred to, the overflow. This valve is generally connected to a pipe that leads from the boiler to the outside of your home. You can usually tell if there’s a problem because water will be coming from this external pipe and therefore out of your system. Over time this small but continuous flow of water will lead to a drop in the water level and water pressure. Even if you repressurise your system, the water will simply leak out again, causing the boiler to again depressurise. PRV’s can also start leaking due to a faulty or uncharged expansion vessel. Usual signs of this are the pressure will increase rapidly on startup then start discharging out of the pressure relief valve at around 3 bar.

Boiler callouts

In order to resolve your boiler problem long term, you will need to get any underlying issues fixed. The problem will only worsen over time and so the longer you leave it, the more likely it is to result in even bigger problems. At Direct Heating Installations, we offer a first-rate boiler call out service in Leeds, Harrogate and the surrounding areas, so if you are having issues with your central heating system, you can rely on us for a speedy and helpful response. With a combined experience of over 35 years, there isn’t a boiler issue that has beaten our adept team yet.

The Direct Heating Installations Team