Hello. I have a Worcester Greenstar 24i Junior Boiler, supplying 5 Radiators and the hot water - 7 years old. A few weeks ago I replaced some of the cold water supply pipe by breaking into the copper pipe just a few feet after the stop cock - inserting several feet of John Guest Speedfit pipe - then connecting back into to the copper again about 6 feet before the copper reaches the boiler supply. Since doing this the boiler has made a clunking sound every time I switch the taps on and off (it happens with both hot and cold taps - bathroom and kitchen) it never did this before the section of copper pipe was replaced. I have bled the radiators and everything is heating up fine. I then checked the mini expansion vessel (A small blue one - Worcester's own I believe) and this had no air in it, pumped some in and could see it was leaking around the join that circles the middle of the vessel - so I need to replace this. My question is do I need to switch it for an identical one - a blue Worcester (about £34) and of the same capacity (about 160 ml) or could I go for another type maybe with a bigger capacity would there be any benefit in doing this ? And my other question is - if after replacing the expansion vessel and if the clunking caused by the taps going on and off continues any suggestions what I should then start looking at? Many Thanks in advance. Geoff.
The device you are refering to sounds like a shock arrestor and not a mini expansion vessel. Firstly do you have a watermeter fitted? And where is the shock arrestor fitted in relation to the boiler, if it has been fitted on the cold water inlet then it definatly is a shock arrestor and can be swapped like for like. If it worked before your intervention into the cold main but is showing physical signs of failure then there is no reason why the same make and size device will not work again.
Thank you for your reply. No I don't have a water meter fitted. The vessel/arrestor is fitted on the cold water supply about 2 feet from where the cold water pipe disappears into the boiler casing. There was NO clunking before replacing the copper pipe - but it started immediately after - as soon as the water supply was turned back on. I have checked all the run of pipe I've had floors boards up in the bathroom and airing cupboard where the boiler is situated - they are all secured to joists and wall with plastic clips I can see no movement and no pipes are knocking against each other. The clunking does seem to be coming from inside the boiler, I assumed it was a mini expansion vessel as that is how it is listed on the various plumbing supply sites I have been looking at. It is exactly like this one: http://www.plumbcenter.co.uk/en/hea...ster-bosch-87161425030-mini-expansion-vessel/
Yes that is a shock arrestor used as specified my most combi manufacturers, they were designed to counter the bounce effect water has when it suddenly stops when the tap is turned off and cannot bounce back beyong the mains stopcock in the street as meters have a non return valve fitted so the water has nowhere to go and bangs about in the pipes. The Mini expansion vessels absorb that shock in the same way an expansion vessel allows expansion to occur without over pressurisation. You should find if installed correctly you have a non-return valve fitted below the shock arrestor, if you dont have a water meter (yet), Im not sure why the installer fitted one but from what you say its failed. I would recommend that you simply either remove the arrastor and non return valve or better still just replace like for like.
Thanks for the reply. The arrestor was NOT fitted with a non return valve - just attached to a small length of copper coming off a T-joint in the water supply. I have attached a closed iso valve as a temporary measure as the arrestor is leaking slightly. But, it looks as though the arrestor is of no use to me, as long as I don't have a water meter. And I could save myself £30+ by leaving the iso valve on as fitting a new arrestor would have no benefit. Thanks again.
You might not have a water meter, but may well have a non return valve within the stop tap in the road. Your installer did the correct thing by installing the shock arrester. Just replace the shock arrester, try your local plumbing suppliers, I pay less than £20 for mine.
Re: clunking noise.go back to basics and fully open stop valve.im guessing you have an old style stopcock with loose jumper and if not fully open, these will clunk when water suddenly stops
Thanks for the reply re stopcock. It is the old style type which I did not touch when I replaced the run of coper pipe. It was seized open and I didn't want to force it. So, I shut the water supply off at the road side. I then inserted a new "full-bore Lever valve" a bit further along from the stopcock before replacing the copper run and use this to shut off the water from inside the house. So, the old stopcock has not been touched at all - is it possible that the road-side main shutting off could have caused the problem you suggest with the stopcock ? Thanks.
Well, I fitted a new stop cock over the weekend and the boiler is still making a clunk/thud sound when hot and cold taps go on and off. So, I can now rule that out along with the pipe run being secure /clipped. I have ordered a new replacement mini expansion vessel/shock arrestor and will give that ago when it arrives..
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