OT - any plumbers on here ? Boiler advice...

My combi boiler is constantly losing pressure, within 12 hours of topping up. Theres also a constant leak from the pipe sticking out the side of the house when the system is running. Im lead to believe that this is a broken Expansion vessel. is this a costly job ?


boiler is 10 years old and have also been advised it could be more cost effective in the long run to change the whole boiler. Theres Baxi boilers with 10 year warranties which would mean i wouldn't need to get monthly cover for maintenance on it.

any advice gratefully received.

As far as I know the pipe sticking out the side of the house indicates you've got a condensing boiler, it's normal that when the boiler is running the pipe will drip. Check for leaks in the system, ie rad valves.

The pipe is the drain for condensation, that’s normal. The loss of pressure is prosbably just be a leak in the system. Have you checked your bleed valves?

Thanks for the advice guys. I’ve been around all the radiators etc over the last few months. Can’t find a thing. Topped it up several times , and it’s empty again in a matter of 12 hours.

The rate the water is coming out of the pipe is quite rapid. Enough to leave a stain on the brick work.

Will keep an eye on it and check again tomorrow.

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Originally Posted by Fine Lines

My combi boiler is constantly losing pressure, within 12 hours of topping up. Theres also a constant leak from the pipe sticking out the side of the house when the system is running. Im lead to believe that this is a broken Expansion vessel. is this a costly job ?


boiler is 10 years old and have also been advised it could be more cost effective in the long run to change the whole boiler. Theres Baxi boilers with 10 year warranties which would mean i wouldn't need to get monthly cover for maintenance on it.

any advice gratefully received.

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The pipe sticking out of the wall that is leaking water is nothing to do with the condensation pipe. If it is a condensing boiler you have, then the condensing pipe will be either connected to your drainage system or running into a soak away.
The leaking pipe is known as a blow off pipe, and is part of a safety device on the boiler. Your 1st assumption about the pressure vessel is probably correct. As someone above has mentioned, air can be pumped into it with a bycycle pump to re pressurise it, or it may need replacing.
It sounds as though you pay a monthly payment at the moment for maintenance cover? If so, why not get them out to look at it?
New modern condensing combi boilers are now getting so well made, that the warranties you get with them are a lot longer, and as you say can be upto 10 yrs now. IMO the Worcester green star models are the best on the market although can cost upto £1200/1300. As in most things in life though, you get what you pay for.

thanks for the replies. Ive been around the radiators again, checked with toilet paper over night, and no sign of any leaks. Re pressurised the boiler this morning back up to 2 Bar (bang in the middle of the green zone). Turned the boiler ron and pressure goes up to 3 Bar (start of the red zone) . Upon checking the blow off pipe its dripping pretty fast out of there, I assume this is the boiler depressurising itself maybe? ill check the overall boiler pressure late this evening.

I don't have maintenance plan, Hate paying for something that I don't use. Ive contacted several local plumbers who haven't got back to me or haven't turned up. So i was thinking of getting a maintenance plan just to have a reliable option.

Had the boiler approx 10 years , its been well serviced every year. Had a couple of problems with it, nothing major though. Just concerned its getting to that age where things are starting to go wrong. Its a Worcester Greenstar boiler. I was hoping to get another 5 years out of it at least. Is it a costly fix the expansion vessel thingy?

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Originally Posted by William Treseder

The pipe sticking out of the wall that is leaking water is nothing to do with the condensation pipe. If it is a condensing boiler you have, then the condensing pipe will be either connected to your drainage system or running into a soak away.
The leaking pipe is known as a blow off pipe, and is part of a safety device on the boiler. Your 1st assumption about the pressure vessel is probably correct. As someone above has mentioned, air can be pumped into it with a bycycle pump to re pressurise it, or it may need replacing.
It sounds as though you pay a monthly payment at the moment for maintenance cover? If so, why not get them out to look at it?
New modern condensing combi boilers are now getting so well made, that the warranties you get with them are a lot longer, and as you say can be upto 10 yrs now. IMO the Worcester green star models are the best on the market although can cost upto £1200/1300. As in most things in life though, you get what you pay for.

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I’ve got a greenstar condenser boiler and as you say the pipe runs down to the drain

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Originally Posted by Fine Lines

thanks for the replies. Ive been around the radiators again, checked with toilet paper over night, and no sign of any leaks. Re pressurised the boiler this morning back up to 2 Bar (bang in the middle of the green zone). Turned the boiler ron and pressure goes up to 3 Bar (start of the red zone) . Upon checking the blow off pipe its dripping pretty fast out of there, I assume this is the boiler depressurising itself maybe? ill check the overall boiler pressure late this evening.

I don't have maintenance plan, Hate paying for something that I don't use. Ive contacted several local plumbers who haven't got back to me or haven't turned up. So i was thinking of getting a maintenance plan just to have a reliable option.

Had the boiler approx 10 years , its been well serviced every year. Had a couple of problems with it, nothing major though. Just concerned its getting to that age where things are starting to go wrong. Its a Worcester Greenstar boiler. I was hoping to get another 5 years out of it at least. Is it a costly fix the expansion vessel thingy?

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A new expansion vessel for your boiler will cost in the region of £100, plus cost of heating engineer/plumbers labour. If the flue on your boiler is vertical, it should only take an hr at the most to replace it. If the flue is horizontal and crosses over the expansion vessel then that will take longer, as the flue will have to be removed and replaced (and tested again)
You could pump up the pressure in the existing vessel with a bycycle pump to buy some time, but ultimately you will have to replace the vessel or the boiler if you choose to.
Beware if you try to get cover on a boiler that already has a problem like yours, as some companies will give you cover, fix existing problem but will want you tied into a long term contract.

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Originally Posted by ninianclark

get some toilet paper and tie some around every rad inlet / outlet in the house - to check for leaks, some leaks the water will evaporate - so you will not see them. When the system is running how high does the pressure go ?

If it goes really high ie above 3bar then the expansion may have a problem, on some boilers you can just pump some air back in - but it depends on the boiler.


I would just get it serviced , they need servicing once every couple of years.

I have a number if you are Cardiff based, he's semi retired now - but very straight up with his advice.

PM me if you want it

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Quote:

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Originally Posted by William Treseder

A new expansion vessel for your boiler will cost in the region of £100, plus cost of heating engineer/plumbers labour. If the flue on your boiler is vertical, it should only take an hr at the most to replace it. If the flue is horizontal and crosses over the expansion vessel then that will take longer, as the flue will have to be removed and replaced (and tested again)
You could pump up the pressure in the existing vessel with a bycycle pump to buy some time, but ultimately you will have to replace the vessel or the boiler if you choose to.
Beware if you try to get cover on a boiler that already has a problem like yours, as some companies will give you cover, fix existing problem but will want you tied into a long term contract.

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Great. Thanks for the help. Think I will try get it fixed and squeeze a few more years out of it.