How to Repressurise a Boiler (Easy Solution)

A boiler should give you proper reading between the two bars of atmospheric pressure. Water pressure indicator should show you the accurate measures. But sometimes central heating starts to show problems.

That’s when you discover your Combi boiler is downing with a sudden loss of water pressure. If you see pressure is below bar one or above two and a half, then the boiler has issues.

To augment or decrease the water pressure with a top-up system you should follow some easy instructions. Here’s everything you need to know about how to repressurise a boiler.

How to Repressurise a Boiler

Figuring Out the Real Culprit!

To solve a problem, you definitely need to know why it exists. Sometimes trying and failing continuously is mere because we don’t give enough attention to the root of issues. Let’s not do that and have a thorough look at your boiler’s system.

Most of the time the criminals behind pressure downing are two. One is leaking and the other is bleeding radiators.


You should check if there is some leaking problem in your boiler system. There may be some tiny leak hiding inside and you are not giving notice to it. This might be the main reason for a gradual drop in pressure. There are very fewer cases of boiler pressure too high and leaking.

You need to have a good look over pipes, radiators and the boiler itself to see if there is any damp patch existing. However, ignore the internal parts of your boiler and never open that. Get some help from a gas safe engineer in that case.

If you have no clue about such handlings then better would be to call someone for help. Dealing with internal parts to top up pressure is going to be risky.


Once you bleed your radiators it will lose some air. This makes the whole system to lose pressure. If you have got into some bleeding recently and facing pressure low issues then maybe this could be the reason.

Checking Pressure Readings!

There is usually a water gauge system available in front of the boiler. This is most of the time hydraulic pressure gauge. If you have one of these then there should be a red section indicating hot water boiler pressure too low.

There is also a section to signal hot water boiler pressure too high. A red indicator needle will show you reading.

You need to make sure it shows a normal boiler pressure range. There are some digital gauges available that shows flashing reads. You will probably get a warning for too high or low pressure.

When the Pressure Is Too High!

If you see the reading is above 2.75 bar then this means it is indicating a high pressure. In this case, you should use the bleed radiator factor to bring it down.

It should be somewhere around 1.5 bars. High water pressure temperatures are dangerous to deal with. So sometimes it tends to be risky handing yourself. Be sure you are giving enough attention while dealing with such pressure.

When you are reducing pressure, a radiator may need some time to bleed. There be some method using which you can catch the water. This will help you to get rid of any wall or floor coverings damage.

When the Pressure Is Too Low!

If you see the pressure is reading less than one bar then it’s a loss of water from system. You need to make a way for replacement, Here the filling loop should come in handy. These are also known as filling the link.  Here are some simple steps to follow.

  1. First of all, you need to make sure the boiler is switched off. The system needs to be completely cool.
  2. You should see valves at both ends of hose. Make sure these valves are completely attached with the hose.
  3. You can use a flat screwdriver or tap handles to simply open valves.
  4. Now use each valve to let cold water get into the whole system.
  5. If there is a sound of water filling system then you are going on the right track.
  6. Keep on doing so until you see the pressure reaching 1.5bar.
  7. Now simple close each valve and make sure to do this securely.
  8. The pressure now should be normal.

Always Check Manual!

No matter what type of problem you are dealing with a good precaution is checking the manual. You should make sure that the system is safe to repressurize yourself.  If you are not sure about using a tool and feel less confident, stop. Let an expert gas safe engineer deal with it.

Still Not Working?

Sometimes the problem does not lie within the boiler but appliance you use. There is a valve known as pressure relief. This helps to get water out from the boiler. Once the pressure is high it releases water.

You can see a discharge pipe that actually routes from this valve. Sometimes the valve gets broken and then it cannot release water for temperature altering. So, you may come around the messed pressure of boiler for that reason.

If this the issue then you need to go for help. Get someone to fix your valve since this might need a replacement.


Boilers are an important tool for so many reasons. It needs to maintain good pressure to serve properly. If you come around defects with pressure then be concerned. It’s a serious problem that might cause dangerous accidents. Sometimes the hot water even blasts.

So, don’t let that happen and always have a check with the pressure levels. Once you figure out a problem fix it out as soon as possible. Manually doing the re-pressurizing yourself is okay unless you can’t relate to boiler’s parts. Asking an expert for help is one of the best choices around.