How urgent is this boiler issue?

[Wingedharpy]

Gas combi boiler heating radiators beautifully but pressure in boiler rises into red zone when boiler running ie. starts at 1 and rises to approx 3.5.
I've turned it off now and pressure has dropped to low side of normal ie. lower than it was before I put heating on.
Anything I can do/check myself to rectify?

Will ask my boiler chap to come and look at it if not, meanwhile would it be OK to use it to prevent hypothermia?

Hot water not affected by any of this.

Grateful for all thoughts.

So in ours there is a balloon that expands to take the expansion in the system from heated water, I suspect that may be a problem. If it needs replacing I think ours was north of £100 before labour. Don’t know if you could do long term damage.

Ours has a problem with the expansion vessel but it’s so old it can’t be replaced. Plumber says that the boiler dumps water out the pipe at the back when it gets too high. We are going to have to bite the bullet and replace it soon.

It does sound a lot like an issue with the expansion vessel. Very often it can be pumped up like you would a tire on a bike. It’s worth noting that this would normally be done at a boiler service. (Especially if you stand behind the engineer and ask if they have done it).

sometimes the issue will reoccur in the same way a pumped up tire will go flat again within a couple of days but it may be a chance to kill two birds with one stone.

Thank you for your comments.
@Volterra : do you still use your boiler despite this issue?

@Droven : boiler was serviced earlier in the year but had no problems then. No bike pumps were used, to my knowledge.

Currently yes we do, he said it was ok to and said it would limp on for now. I wouldn’t rely on this though just in case yours is different but hope it gives you a bit of hope you may not have an immediate big bill.

Thanks @Volterra .
Phoned boiler man to check it out but he can't come for 2 weeks.
Will avoid using it as much as possible for now.
Using electric heater to prevent hypothermia.
Can see £5 notes burning in my minds eye!

Hi OP, had this with mine and turned out to be a pipe that hadn't been replaced properly and a leak was making pressure rise. Man who did the boiler services told me it was safe to use but as it was under warranty boiler co would have to fix it (and thanks to lockdown couldn't get the boiler co out for months).