Worcester Bosch boiler pressure dropped to zero

[nell15]

Any ideas? It's only 3 years old and is annually serviced.
It was fine then we realised the heating hadn't come on last night. I re- pressurised it - although half an hour after I'd done this the gauge shot up to high and I had to take some water out by bleeding a radiator
This morning it's back to zero

It's booked for a service early November
Should we get someone out sooner or can we fix it ourselves?

[tribpot]

I'd get someone out. To my untrained eye I'd wonder if there was something wrong with the gauge given it went from low to high to low.

I looked on the Worcester Bosch home page and they had a few suggestions, maybe give them a call?

[nell15]

.Thanks Tribcot I think we'll have to get our usual plumber out. We just don't want to drag them out on a Sunday if it's something we can fix ourselves

[nell15]

Sorry I spelt your name wrong Tribpot

[Saucery]

We had this problem and I think it was a diaphragm affecting the pressure. Quite cheap to fix but did need our boiler company to come out and look at it, so maybe move the service forward to this week if possible?

[SuburbanRhonda]

Ours has been doing this ever since the annual service last week

[Auriga]

There's a video on the he website that shows you how to top up the pressure. The system has to be cold. I only top up to 1.5 because it will go higher when it's warm. Ours drops all the time, because there's a leak somewhere we can't locate.

[Meadows76]

The OP already knows how to top up the pressure. She did it. It fell again.

OP our old boiler did this and we got the man out, turned out there was a leak of minuscule proportion in the pipe under the boiler. We never even had a wet bit underneath it but he found a hole there!

[enolagayits0815]

Have you got a slow leak somewhere? We had the same problem and that's what it was.

[GlowWine]

Our pressure drops have always been due to leaks in the pipes somewhere. Have a close look at your ceilings, pipes, connections etc. I topped up and ended up with water cascading through the ceiling because a joint had given way. Several years after installation.

[PigletJohn]

In this case, pressure going unusually high when hot, then dropping away when cold, indicates the expansion vessel is either faulty, or needs pumping up.

It is not indicative of a leak.

[Monkeyinshoes]

Had our Worcester Bosch for 7 years and it's done the exact same thing twice now.

Both times it was a blocked pipe to the expansion vessel, this sends the pressure too high, it vents out of the pressure release valve (or you let some out of the radiators) and then it's too low when cold.

You can't fix this yourself, you need a plumber to check the expansion vessel and the pipes leading to it.

[johnd2]

Yes what piglet John said, it's a problem with the expansion vessel. If you're not complement to do it yourself, while you're waiting for a plumber you can drain a radiator you don't need as much and then don't bleed it when you top up, and only open one valve on it. Then it will act like a temporary expansion vessel until you get it fixed.

[nell15]

Thanks everyone the power of mumsnet!! The pressure is still dropping to zero despite topping it up 3-4 times. We've rang the man who's coming to service the boiler in November. He can't come sooner and suggested we ring Worcester Bosch and they're sending someone out today