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Boiler Keeps Losing Pressure


Having no water is a nightmare no homeowner ever wants to go through. But unfortunately, even with boilers, homeowners have to suffer through the use of cold water. When this happens, the most common culprit is the loss of water pressure.

Fortunately, low boiler pressure is a problem that is easily fixed if you immerse yourself to learn the quick fixes. In this guide, we’ll guide you through solving common causes of low boiler pressure problems.

What is boiler pressure?

Boiler pressure is a balance of air and water in the boiler system. For a boiler to function efficiently, it needs a specified balance of air and water. You can think of it as the Yin and Yang. Without optimal boiler pressure, the system will not heat your home or offer hot water.

If the pressure is too low, the water will not flow into the radiators for heating. And if the pressure is too high, then the water will leak through the joints and seals.

Did your boiler lose pressure overnight?

A boiler losing pressure is a common occurrence. They lose pressure from time to time and require a top-up. If this is your first encounter with boiler pressure loss, you should relax. A quick top-up (repressurizing process) will do.

To check if the boiler has low pressure, glance at the pressure gauge located at the front panel.

What is the normal pressure gauge?

Once the boiler is off, the pressure gauge should be on the green zone. This is between 1 and 2 bar. When the boiler is heating your house, the pressure will increase. But once it is off and it cools, it will drop back to normal.

How to repressurize a boiler

Repressurizing a boiler is the quick fix for boiler pressure. The process is simple and takes a few seconds. Below is a step by step guide on how to go about it.

Step 1: Find the filling loop

The filling loop is a silver Flexi pipe that has black taps (either one or two). The filling loop is located under the gas boiler and is usually among other pipeworks.

Step 2 – Increase boiler pressure

To increase the boiler pressure, you should open the black taps until you feel them lock at a 450 angle. Once the tap is open, the boiler pressure should start to rise towards the 1 bar point.

Step 3: Close the tap

Once the pointer is at the centre of the green zone, close the black tap. Make sure to take the tap back to the original position. Leaving it half-closed will cause a drop in pressure in no time.

Common faults for boiler keep losing pressure

If the boiler pressure is dropping fast and often, even after you repressurize the boiler, it means there is a deeper issue you need to attend to. Some of the most common boiler faults that cause a constant loss in boiler pressure include;

A leaking system

If the boiler system leaks, it can be challenging to spot it. The leak can be anywhere on the pipes or inside the boiler. It could be a small or large portion. Also, the leak could be under the floorboards or within the walls.

How you can identify the leak in the boiler

To determine where the leak is, follow the pipework throughout the house. Be on the lookout for any leakage. Pay more attention to the bends and the joints of the pipework. This is where the seals are and where high pressure can weaken with time and give way to a water leak.

How to fix the leak

A leak in the boiler system, especially those that are internal should be left to professionals to attend to. The Gas Safe engineer will re-pipe and reseal the system. However, if the boiler is older than 10 years, we suggest that you buy a new boiler. It will save you money in the long run, mainly because new boilers are energy efficient.

Faulty safety devise in your boiler system

From time to time, the internal parts of a boiler will fail. It is an occurrence that manufacturers prepare for. Many manufacturers today include built-in fault codes that are displayed on the monitor. These codes make it easier for the Gas Safe engineer to diagnose the problem and fix it ASAP.

Fixing broken parts of a boiler

Usually, a faulty component in a boiler is removed and replaced with a new part. The replacement parts have varying prices and depend on the age of the boiler, the part and the availability of the parts. For instance, if the heat exchanger needs to be replaced, you will spend a lot of money to get a replacement. Because of this, we advise getting a new boiler instead.

On average, the cost of repairing the boiler is between £300 and £500.

Note: loss of boiler pressure happens with any boiler even with the most renowned and popular brands in the industry. In the next section, we look at the standard error codes you might come across.

Is this issue common in Vaillant, Worcester, Ideal and Baxi boilers?

Loss of boiler pressure occurs with all boiler types and brands.


The error codes relating to boiler pressure loss on Worcester Bosch boilers include; A1, H07, 207, E2, CE, 2970B, 224 V, 2971B. These pressure codes apply to Worcester boilers including; Worcester Bosch CDi Highflow, Worcester Bosch CDi Classic, Worcester Bosch Greenstar 25i. Worcester Bosch CDi Compact, Worcester Bosch Greenstar 30i combi and Worcester Bosch CDi Classic Regular.


Boiler pressure error codes include: F.12, F.24, F.22, F.23 and F.25. These error codes apply to Vaillant EcoPure, Vaillant EcoTEC, Vaillant EcoTEC Plus, Vaillant Turbomax Plus, and Vaillant EcoTEC Plus Regular.


The boiler pressure error codes include; E119, E28, 118, H.02-06, 119, E.02-07 and E118. These codes apply to Baxi 400, Baxi 200, Baxi 600 Combi, Baxi EcoBlue Advance, Baxi Platinum, and Baxi DuoTec.


The boiler pressure error codes for pressure loss include; F1 and Water Pressure (displayed on the monitor). The pressure codes apply to Ideal Isar, Ideal Logic Pus, Ideal logic, Ideal Vogue Max, Ideal Vogue, and Ideal Mini

Do I need a new boiler?

It all depends on the cause and the extent of the damage. In the case of internal and external leaks from the joints and leaks, and faulty parts, it’s not mandatory to buy a new boiler (not unless the boiler is more than 10 years old).

However, if a faulty heat exchanger causes pressure loss, you might have to buy a new boiler system. Heat exchangers are expensive. It makes more sense to replace the whole system than the boiler part.


Though boilers are designed to last for long, they don’t last forever. The longest high-quality boilers last is a decade and a half (and that’s with proper maintenance). However, supporting a boiler that is close to dying can be costly.

Because of this, you need to do several things before buying a new boiler. These include:

  • Reading through boiler reviews
  • Get multiple quotes to compare and get the best deals
  • Research on the best boiler to purchase
  • Weigh the cost of a new boiler against the cost of repairs under warranty.

If you can fix the boiler easily and affordably without a chance of it breaking down in the near future, then repairing the problem is your best option. Old boilers are usually expensive to repair.

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