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Guide | How to re-pressurize boiler

Low boiler pressure can be really frustrating as it not only leads to delayed household heating but reduced overall efficiency of the central heating system, resulting in high bills for nothing! Therefore, it needs to be fixed as soon as possible to tackle the current situation as well as to avoid further complications. 

In this particular, we will give you a quick guide on how to diagnose, fix, and repressurize your low-pressure boiler with factors that cause it. So let’s get on with it:

Here’s a simple, step-to-step guide you need to follow to carry out the cleaning procedure in the right way

Causes of Low Boiler Pressure

Although there are numerous causes for low boiler pressure, two are the most common reasons often faced by most boiler owners. And luckily, they can be easily fixed even if you are the least qualified person for the job. So here are they:

Water Leaks

Water leaks are one of the most common for low water pressure. Although you have to consult a Gas Safe Engineer to spot the leaking sites inside the boiler or radiator, you can still identify them by looking for damp patches throughout the household. If that’s the case, you might need a proper repair job. You can rely on Serviceteam London for the job.

Bleeding Radiators

On one hand, where Bleeding radiators ensure optimum pressure by releasing air, it can also be a reason for low pressure if done more than the intended limit. Therefore, make sure the boiler is bled properly with acceptable water and air release, as excessive bleeding will lead to certain complications. 

Other Complications

If you carry out a proper checkup but still unable to identify issues related to bleeding or water leaks, it might point toward other complications needed to be fixed by consulting a qualified Gas Safe Engineer. Just in case you feel like needing one, Call Serviceteam straight away. We provide the best boiler repair and maintenance services all across London with a highly professional team of experts and customer-friendly staff. You’ll be left with a smile! 

What is optimum Boiler Pressure

Normally, a boiler operates between 1-2.5 bars. Any pressure reading less than one is considered low while more than 2.5 bars are considered high. However, if your boiler is caught in any of the aforementioned conditions, its time to get it checked-up as both are equally harmful to the central heating system.

How to check the boiler pressure

There’s a water pressure gauge on the front side of the boiler. If your boiler has a digital gauge, it will give you a flashing pressure reading which is a clear indicator towards low or high pressure. However, in terms of hydraulic pressure gauge, high or low pressure is indicated by red sections on the dial. Just keep it in check and take the necessary steps in any of the aforementioned cases.

How to repressurize your boiler

Since there are a lot of boiler brands, each functioning differently than the other. Therefore it’s of extreme importance to read the boiler manual and follow the manufacturer’s instructions. Good brands also have useful videos posted on their websites for their customer’s ease. Make sure you check them out! 

Here are some step-by-step methods you need to try before consulting a professional:

Repressurizing boiler with external loop:

Here’s what you have to repressurize the boiler with external loop:

  • Take the hose and attach it to each side of the hose.
  • Once the hose is attached, open the mains cold water valve, followed by the valve that connects to the heating system.
  • Leave both valves open until the pressure reaches to 1 bar.
  • After you’re satisfied with the pressure, make sure you remove the hose and close both valves.
  • Even if the pressure goes above 1 ar, be satisfied as it can be corrected later with bleeding.

Repressurizing Boiler with a keyed internal filling loop

Well, this method is primarily recommended for the Worcester Bosch model, however, it is applicable to any other model that has been provided with a special key as a part of the installation. Here’s what you have to do:

  • Locate the key, usually found in flap underneath the boiler.
  • Find the key-fitting point. Usually located at the front, right-hand side.
  • Align the arrow on the shaft of the key with the open padlock position. Once the key is completely engaged, try turning it to the closed padlock position.
  • Once the key is in its position, open the white port situated to the left of the key port.
  • Watch the pressure rise to 1 bar. Once its done, close the tap immediately.
  • Turn the key back to the open padlock position and remove the key.
  • Water dripping is normal after removing the key.

It is one of the most effective ways to repressurize the boiler to normal.

Repressurizing Boiler with a keyless internal filling loop

Just another easy trick to repressurize the boiler. Here’s how you do it:

  • Identify the keyless with the help of a blue lever at the bottom of the boiler.
  • Pull down the lever until the pressure is just over 1-bar.
  • Once done, release it.
  • Even if the pressure exceeds 1-bar, you can get it back to normal by simply bleeding the boiler.

How often should the boiler be repressurized

There’s not a certain timing for repressurization. Just do it when you feel the boiler’s pressure to be tunning too low. Moreover, do make sure to check after each passing week to ensure everything’s running safe and sound. Just in case you have to repressurize the boiler too often, it points towards a possible leak in the system which needs to be fixed. You can also consult our Gas Safe Engineers to tackle the situation! 


Is it normal for the boiler to lose pressure?

Actually, NO. Most, or almost all the times, it occurs due to certain leaks. Since spotting the leak points is an arduous task even for DIYs, it’s preferable to consult a Gas Safe Engineer to perform the task.

Can a boiler lose pressure without a leak?

Unless there is some fault in the boiler, it is not possible to lose pressure without a leak. If you don’t detect any leaks even after a thorough check, its time to get the boiler checked part by part to identify and repair the fault. 

How to find a leak in the central heating system?

To find a leak in the central heating system, just place a colored paper underneath the boiler and see if there are any water drops appearing on the paper. If you see any, just follow the wet spots up along the central heating system and you will find the real leakage spot.

Can you bleed a radiator when heating is on?

No, you cannot bleed a boiler with the heating being turned on as it may be too hot to touch, resulting in some serious burns if not handled carefully. Therefore it is preferable to turn the heating off while bleeding a radiator. 

What happens if the pressure is too low?

Pressure lower than the minimum limit will lead to a boiler malfunction. Therefore it is recommended to keep the pressure to at least 1-bar, which is the least pressure.