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Why is my boiler losing pressure? Combi boiler pressure - The top 10 questions to boiler pressure

Martin Smith the Emergency Plumber answers your frequently asked questions on "Why does my combination boiler lose pressure?" The fact is that your boiler is losing pressure because there is a leak in your system. The questions below are the top 10 questions to ask about the boiler pressure which we try our best to give the best answers below.

1. My combi boiler is losing pressure? - This is the most asked question when searching the internet and we are here to answer your questions as follows:

2. Combi boiler pressure - This is the second most typed in question when looking for an answer.

Combi Boiler relief valve

3. What should the pressure be on my boiler?

4. Why does my boiler keep losing pressure?

5. Why is my boiler losing pressure?

6. Boiler losing pressure no leak?

7. What pressure should my boiler be?

8. How to release pressure from my combi boiler?

9. My boiler is losing pressure?

10. Where do i pressurise the boiler?


How do i release pressure from my combi boiler? In answer to question 8: To release pressure you will need to either turn the valve as shown in the picture above (please take note we only advise a qualified Engineer to do this) or you can open up a radiator drain off valve which will also take away pressure from your radiator system.

Is your combi boiler losing pressure? In answer to questions 1/ 4/ 5/ 6/ and 9: This is because there is a leak on the central heating system which can either be due to corrosion on the pipe, leaking valve due to the gland on the radiator valve not being used or turned for a while or the pressure valve is not shutting properly. How to fix this problem? The easy way to fix this is to use a central heating liquid which goes in to your central heating and may take up to a couple of days before the liquid does it's job in stopping the leak. Make sure you check all your valves that have recently been turned on. Make sure there is no corrosion going on, check the pressure pipe outside to make sure theres no water dripping.

Sometime's trying to find a leak is not easy and it may be advisable to call a Plumber out.

What should the pressure be on my combi Bolier? In answer to questions 2/ 3/ and 7. The pressure on the combi boiler should be at 1.5 bar or between 1 bar and 2 bar. If the pressure goes below 1 bar, then sometimes depending on the combi you have then the boiler will not operate. This is a safety device to stop your boiler from breaking. If the pressure of your boiler goes higher than 3 bar then the pressure release valve will open and you will find water coming out of the pipe which is located out side.

Combi Boiler relief valve

Where do i pressurise the boiler? In answer to question 10: To pressurise the combi boiler up in most circumstances then you will need to find a filling loop as pictured to the right of you. You will need to quarter turn the valve to let water through until the boiler is at its recommended pressure or where the red need is set at.

Just below here is abit more about this page which i had previously written which you may find of good use.

To fix the leak first you need to determine where the leak is coming from. The first thing I Martin Smith the Plumber would do is check the blow of pipe outside is not letting water out. This should be 6 inches from the ground floor, in most cases when incorrectly fitted which is most of the time you will see a 15ml pipe sticking outside the wall.

If there is no leaks here then you need to go round checking all your pipes, this also includes your radiators to see if there is weeping. The tell tail signs for this is corrosion. For your central heating system to go from one and a half bars to zero you would have to loose an approximate 1 pint to 2 litres of water. This also depends on the capacity of the central heating. The pressure release valve which if turned can lose the pressure from the boiler.

What happen's if i can not find the leak and i can not stop my combination boiler from losing pressure? Sometimes the leak can be hidden, but there is sometimes another solution, as long as the leak is very slow you can put in a liquid that seals up the leak, this may take a couple of week's to completely stop. I would like to mention when doing this to make sure you have no really black water or sludge in your system, if theres black sludge we would recommend you clear this out.

Sometimes it has been known for example, some people have central heating pipes buried under the concrete floor, to find a leak is almost impossible, this is due to incorrect procedures in fitting the system which we advise against.

Some combination boilers don't operate when the pressure is below 1 bar, this is a safety device to stop any further problems occurring to the boiler, so always keep your combi boiler pressure above 1 bar and below 2 bars.

Be free to look up more How to Plumbing and thank you for spending the time in reading about How to stop a boiler from depressurising.

In this i have included a picture of a filling loop.

Thank you to Steven Blair (twitter.com/blairy1975) for inspiring me to write the How to Plumbing about the boiler pressure.

Emergency Plumber Martin Smith.