I have just had my year old Worcester, condensed combi boiler, Greenstar i Erp serviced by the installer. He seemed surprised when I said I have a water meter. He then told me that I should really have a shock arrester fitted as I have high pressure. He claimed, he only found out about this issue a few months back and didn’t know at the Time he fitted the boiler. Does anyone know if this is correct?
Shock arrester
- Thread starter 32tybeams
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Not sure about a shock arrestor, I'd probably look more towards a pressure reducing valve.
All depends on high the mains pressure is I guess.
All depends on high the mains pressure is I guess.
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I would think that my installer would know all about the benefits and pitfalls of both the shock arrester and pressure reducing valve and has come to his conclusion by bearing in mind the height of the water pressure. Many articles and posts on this subject mention about noisy, clanging and banging pipes. I haven’t got that problem. My ch system is quiet. And another thing! Wouldn’t the old boiler I had before this one have had the same high pressure problem? After all, the water meter was installed years ago.
Sorry but not sure if you are being adversarial with your reply or not?? If you are, then not sure why you're on asking in a public DIY forum. If you trust your installer then fair enough, I'm just giving you my professional opinion.
Shock arresters are fitted to stop water hammer and absorb hydroshock, pipes banging/vibration through hydraulic action. This can affect seals etc throughout the cold mains supply and HW systems and outlets including the boiler. Shouldn't be an issue though unless it is already prevalent within the house and is already causing issues.
Some boilers do need to be protected against high water pressure, as should the whole hot and cold system within a house and then a PRV is used, that would then protect everything. I have seen that WB and Baxi are starting to recommend them, Viessmann now come with them fitted internally I believe, where a meter is fitted due to the NRV. Personally I see that as a cop out to explain when their parts might fail and another reason to invalidate the warranty, especially if water hammer isn't even an issue. If you're happy to have one fitted then of course knock yourself out, never seen the need.
Shock Arresters are a last resort IMO, water hammer is usually caused by a valve closing too quickly and/or loose/badly installed pipework and is fixed by correcting the valve and/or pipework and by controlling the mains pressure.
Sorry, I wasn’t being adversarial. Please don’t take it that way. You’ve explained everything very clearly. Where you say about the warranty becoming invalid, he did mention that too. Thank you very much. You have been very helpful!
Yes, if your mains water supply or water meter has a non-return valve fitted then you should fit a mini expansion vessel (also called a shock arrestor) between the non-return valve and the combi to absorb any expanding water from the combi that would have been taken up by the water main before the nrv being fitted.
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Makes sense!, I did wonder what the actual problem would be. Good explanation.
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