What to do if your boiler loses pressure

If your gas combi boiler is losing pressure and is running at a lower pressure than it should, it may not be as effective and efficient. There is also a risk of problems developing. Luckily, you may not need to call an engineer out. Here’s a handy guide to fixing your boiler pressure problem safely.

Why do boilers lose pressure?

Gas combi boilers are constantly in use, not only producing hot water on demand, but also pumping water throughout your home to keep your central heating working so that you can stay warm and cosy. Over a prolonged period of time, your boiler will naturally lose some of its pressure so if this is a one-off occurrence, it is normally nothing to worry about. If you are repeatedly losing pressure, you may have a water leak somewhere in your heating system or a fault in the boiler itself. Read on to discover how to identify and fix common boiler pressure problems.

How to find and fix a water leak

In modern homes, most of the central heating pipework is hidden out of sight, either within walls or behind cupboards or panels. This can make it very difficult to spot a leak. There are, however, some telltale signs to look for. These include:

Wet joints

The joint where the pipe is connected to your radiator (underneath the control knob) is the most common location for a leak. If the pipe below the controller feels damp, try tightening the connector nut, dry the pipe and observe to see if water continues to form on the pipe.

Wet patches on your pipe

If you have a water leak, there will usually be a very localised wet patch. If the entire section of pipe is wet, this may be caused by condensation. If you suspect a pipe may be leaking, dry it off, leave a paper towel underneath and observe.

Flaking or bubbling paint

Flaking or bubbling paint on a pipe is another indicator of a water leak. If you notice this sign, dry the pipe (if wet), place a paper towel underneath and observe.

Damaged skirting boards

As well as bubbling or flaking paint, rust marks, stains, lifting, bulging or lifting skirting boards can also indicate a water leak in your radiator pipe. You may need to undertake further work to examine the pipe.

Ceiling stains

In some cases, a slow leak may result in a stain that is visible on the ceiling. If you notice discolouration or other marks on your ceiling that look like they may be caused by dampness, this merits further investigation.

Fixing the leak

If you find a leak in the pipework itself, it is possible to perform a temporary repair using radiator repair tape, which can be found in a hardware shop or online.

It is recommended to get a confirmed or suspected leak examined by a heating engineer as soon as possible so that it can be properly repaired. If your boiler continues losing pressure even after a leak has been fixed, there may be a fault in the boiler.

How to recognise a boiler fault

If you are sure that there is no water leak in your system, it is possible that there is a fault in your boiler. Gas combi-boilers usually use a system known as a ‘filling-loop’ to maintain the cold water pressure from the mains supply. Most boilers are designed to allow the homeowner to regulate the amount of water circulating in the boiler and heating system by manually adjusting the filling loop. This means you can safely restore the pressure in the boiler and heating system if needed without needing to call an engineer out.

Safety first

Before attempting to re-pressurise the boiler yourself, consult your boiler handbook / operating manual.

If you can’t find instructions or are not comfortable performing this procedure, be sure to seek the advice of a qualified engineer.

How to re-pressurise a gas combi boiler

As long as your boiler manual states that it is safe to re-pressurise the boiler, then it is safe to proceed. The process will usually comprise of the following steps:

1. Find the filling-loop and pressure gauge. The filling loop handles should be at a 90-degree angle to the flow of the pipe (usually horizontal).
2. Make sure that you can see the pressure gauge whilst accessing the filling loop. Get somebody to help you if this is difficult. Most sealed systems will operate at around 1.0 - 1.5 bar - there should be a marker on the gauge. It is recommended to consult the manufacturer’s manual for the recommended pressure.
3. Turn off the boiler.
4. Turn both filling loop handles to match the direction of the pipe - you should hear water flowing.
5. Keep sight of the gauge at all times and turn off the handles as soon as the desired pressure is reached. Make sure that the handles are fully closed.
6. Turn the boiler back on and observe.

What if I over-pressurise my boiler?

If you accidentally over-pressurise the boiler, there is no need to panic. You can reduce the pressure back to the correct level by bleeding your radiators. Although it is a straightforward job, it can be time-consuming and is something you’d probably prefer to avoid!

If your boiler maintains pressure once the re-pressurising procedure has been completed, then the problem is likely to have been resolved and there is no further need for concern.

If you still experience pressure loss

If, after following these steps, your boiler keeps losing pressure then this is a sign that there is a fault within one of the components of the boiler which will require the assistance of a qualified engineer. Where this is the case, it is advisable to have an engineer inspect your boiler at the earliest possible occasion to avoid further damage occurring if there is a faulty part.

If in doubt, consult your engineer

If you have any doubts about your boiler losing pressure or are not sure about how to re-pressurise the system yourself, it is always best to consult your heating engineer. Call us today on 01978 291 923 / 01352 620 125 to speak to an expert.