Boiler Losing Pressure - Expansion Vessel

triplebb

Hi,

I've had a gas engineer tell me last time on a routine check that my expansion vessel needs "work" because I'm losing pressure daily. I told him that I repressurise the system daily - let's say I top it up to 1.5 bar and turn on the central heating - it will go to over 3 bar then back to 0 bar after a couple of hours. I said I cannot afford right now to get this fixed, I asked if it's in any risk if I just leave it in this state and he said it's fine, I can just keep topping it up every time I need to use it.

However I would still like to get some second opinion here, perhaps some people here would be knowledgeable to help.

Is it okay to leave it as it is, just top it up every time I need to turn on the heading system or does this need to be looked at as something bad can happen? Do I use more gas this way too or does that have nothing to do with it?

Thank you.

Shaun_of_the_Dead

triplebb wrote: »

Hi,

I've had a gas engineer tell me last time on a routine check that my expansion vessel needs "work" because I'm losing pressure daily. I told him that I repressurise the system daily - let's say I top it up to 1.5 bar and turn on the central heating - it will go to over 3 bar then back to 0 bar after a couple of hours. I said I cannot afford right now to get this fixed, I asked if it's in any risk if I just leave it in this state and he said it's fine, I can just keep topping it up every time I need to use it.

However I would still like to get some second opinion here, perhaps some people here would be knowledgeable to help.

Is it okay to leave it as it is, just top it up every time I need to turn on the heading system or does this need to be looked at as something bad can happen? Do I use more gas this way too or does that have nothing to do with it?

Thank you.

So you trust some random on the Internet rather than your gas engineer?

triplebb

Haha sorry I didn't mean to make it sound like that. Was more like if there happened to be a member who is a gas engineer themselves willing to give me second opinion that'd be great. Like my own gas engineer didn't really open up the boiler or anything, he just turned it on looked what it did, instantly said expansion vessel but said it's fine if I leave it like that. However I always like to get more opinions if possible

cajef

Every time you top it up you are diluting the corrosion inhibitor, eventually it will soon need fresh inhibitor in the system.

triplebb

What does that mean exactly? Can you elaborate? How soon, what happens if I just leave it like this for a year or so?

Undervalued

It depends on how much you are putting in, the size of the system and how strong the inhibitor was to start with! So no easy answer.

An average system might hold 20 gallons / 90 litres of water. A quick pressure top up may only be a coffee mug full, say 0.2 litres.

When your system goes over 3 bar, because the expansion vessel is faulty, it will be venting water out of the overflow. Then when it cools down the pressure will drop and the boiler will cut out. So you top it up, each time replacing what it lost with fresh water. That encourages scale and corrosion.

So, whilst it is not dangerous and a few times won't do significant harm it is not a good idea medium to long term.

jefaz07

It may not need changed, it might need re pressurised, it might need changed or the connecting hose/pipe may be choked giving the indication of a broken vessel!
You won’t use more gas but as stated you are putting oxygenated water back into the system.
Also, is it a nuisance? Does the boiler go to lock out with the low pressure?
Either way it needs looked at.

triplebb

It doesn't lock down or anything, it works as usual, just that I have to top the pressure up daily. i would love to get it looked at but it will cost quite a bit I assume and money is tight at the moment. The only thing I worry is that if I leave it as it is, if some more problems won't raise in the future.

Undervalued

triplebb wrote: »

It doesn't lock down or anything, it works as usual, just that I have to top the pressure up daily. i would love to get it looked at but it will cost quite a bit I assume and money is tight at the moment. The only thing I worry is that if I leave it as it is, if some more problems won't raise in the future.

As I said, a few times won't do much (or any) harm. Doing it daily for weeks on end isn't a good idea as it will encourage scale and corrosion. Also the radiators, or at the very least, the highest one on the system will need venting as air released from the fresh water will collect.

If it was me I would get it seen to within a few weeks, not months or years.

The expansion vessel is a rubber balloon inside a small metal tank of water. The air pressure in the balloon needs to be correct. It may just need pumping up, like a car tyre, very occasionally which is OK if it generally lasts between annual services. Or it may have a more significant leak and need replacing. As has been said, there can be other more unusual problems that can give similar symptoms.

JimmyChanga

When your boiler repairer says it needs work did he actually try re-pressurising it first?

vw100

Your boiler may eventually breakdown, as more air goes in the system and also via the water being topped up. This eventually creates more sludge in the sealed system and eventually cause things like the pump failing, prv valve failing and maybe the more expensive things like the heat exchanger. Best to get a proper fix done.