Worcester 15/19 heatslave pressure

[northernerchris]

I have a worcester 15/19 oil combi boiler which keeps losing pressure.

I've had an engineer to look at it a few times who simply tops the pressure up to around 1 bar and says there'll be a tiny hole somewhere in the system where pressure is escaping. Anyway after he's topped the pressure up, for a few weeks after the boiler will run around 3 bar and sometimes when the hot water tap is used or if the heating goes off there is a huge noise like a sudden release of pressure which causes all the pipes in the house to vibrate for a second or so. Eventually after a month or so the pressure falls to 0 (when the heating hasn't been on) which when the heating is on will reach 1 bar.

I am convinced there is something else wrong with the boiler and after looking on this forum I wonder if it is the expansion tank which is causing the problem. I've pressed the valve on the top of the big orange tank and water comes out, does that mean the expansion tank needs replacing? If so is it a big job best left to the professionals or can a diy'er do it? If its a job for the diy'er where do I start as I've read posts in the past saying don't drain a system from somewhere as that screws up a valve somewhere else and so on!

Also where is the best place to buy an expansion vessel and is there anything else I need to take into consideration before attempting this job?

Many thanks,
Chris

 

[kevplumb]

if your getting water out of the valve yes

looking at the mi's it don't look to difficult


mind ive never done one

 

[oilman]

Does he "simply top the pressure up", or does he first check the expansion vessel air pressure? If he doesn't, get someone else in future.

To check the expansion vessel for water, lift it clear of the boiler and turn it upside down. depress the valve (or remove it) and a bit of water might come out, but should then stop. Put some pressure in the system and no more water should come out. If it does, new vessel, if it doesn't, release the water pressure using the PRV and pump up old vessel.

 

[kevplumb]

if its coming out of the valve at the top when its in pos

why turn it upside down

not a dig just curious

 

[wilhelm]

blimey kev, youre risking it, just as well you said ,not a dig

as you know , we can turn into rabid dogs, instantly.

I think he means to make sure even the slightest bit of water will be found , if its tipped upside down.?

I just prod the scrader, with ev in position and low and behold i need one of these

 

[oilman]

You really need to take the valve out and put a new one in. They're pretty poor for use in expansion vessels and cause problems. I turn them upside down so all the water comes out, including the bit that would otherwise stuck in the valve stem. Can't justify it, it's just what I do.

 

[kevplumb]

fair enough if you don't ask you never learn