joe90 Posted June 27, 2023 Share Posted June 27, 2023 To be more specific, the boiler fires up briefly when I turn the sink cold water tap off. I do have high water pressure, reduced to the kitchen tap and outside tap but nearly 8 bar everywhere else (brilliant shower 🤔). Do I need to reduce the pressure elsewhere? Link to comment Share on other sites More sharing options...
Temp Posted June 27, 2023 Share Posted June 27, 2023 Perhaps when you turn off the kitchen sink cold tap a shock wave travels back through the cold main to the boiler and through the flow sensor. Does it do it if you turn off the tap really slowly? If that's OK perhaps fit an anti thump device on pipe to the tap? Link to comment Share on other sites More sharing options...
joe90 Posted June 27, 2023 Author Share Posted June 27, 2023 (edited) 4 minutes ago, Temp said: Perhaps when you turn off the kitchen sink cold tap a shock wave travels back through the cold main to the boiler and through the flow sensor. That makes sense, tried fast and slow but it does not happen all the time so difficult to see. Yes when I turn it off fast there is an audible click from the boiler. Never heard of an “anti thump” device, I suppose it’s similar to water hammer 🤷♂️ Edited June 27, 2023 by joe90 Link to comment Share on other sites More sharing options...
JohnMo Posted June 27, 2023 Share Posted June 27, 2023 Mine clicks on, then off when I was filling the central heating, the fill valve is in the cold water line into the combi. Think the flow switch in the boiler must see a slight reverse flow. Maybe we should have a check valve in the line? 1 Link to comment Share on other sites More sharing options...
Temp Posted June 28, 2023 Share Posted June 28, 2023 6 hours ago, joe90 said: Never heard of an “anti thump” device, I suppose it’s similar to water hammer 🤷♂️ Yes that exactly what I mean. 1 Link to comment Share on other sites More sharing options...
PeterW Posted June 28, 2023 Share Posted June 28, 2023 At 8 bar I would fit an inline PRV and then a small potable expansion vessel somewhere to reduce the pressure to 3-5-4 bar max in the house. It won’t reduce the flow that much, and you’ll not have the pressure bounce on the flow switch in the combi that you’re getting today. 2 1 Link to comment Share on other sites More sharing options...
Conor Posted June 28, 2023 Share Posted June 28, 2023 Is your pipework mostly copper or plastic? By shutting off a high flow under high pressure, you create a pressure wave (surge) the propogates back downstream. In the water industry we use either surge vessels (bit like a large expansion vessel) or a surge relief valve. These deal with the shock wave by allowing it to push the water in to an empty space. In a closed system like yours, there's nowhere for the water to go so the energy is transferred in to the pipework and attached applicances. Not normally needed in a domestic setting tho, either turn your tap off slowly or reduce your pressure down to 3bar. I'd be doing the latter as you're also reducing the risk of a leak by a factor of several (there's a graph somewhere with failure rates and pressure.) 2 Link to comment Share on other sites More sharing options...
joe90 Posted June 28, 2023 Author Share Posted June 28, 2023 I think I will move the PRV that I fitted to the kitchen tap and outside tap only to the incoming supply and find a balance of pressure that gives a good shower but controllable elsewhere, I have noticed when the loo finishes filling there is a real thump within the pipe work. 4 minutes ago, Conor said: you're also reducing the risk of a leak. Yes I agree 👍. Link to comment Share on other sites More sharing options...
joe90 Posted June 28, 2023 Author Share Posted June 28, 2023 16 minutes ago, Conor said: Is your pipework mostly copper or plastic? Sorry didn’t see this, copper. Link to comment Share on other sites More sharing options...
joe90 Posted July 10, 2023 Author Share Posted July 10, 2023 Not got around to this but putting this before my boiler was suggested by a plumber friend. https://www.screwfix.com/p/sioux-chief-dw660-2j-water-hammer-arrestor-1-2-bsp/1492r Opinions! Link to comment Share on other sites More sharing options...
SteamyTea Posted July 10, 2023 Share Posted July 10, 2023 41 minutes ago, joe90 said: Opinions Looks similar to the medicine the French Doctor gave me. Is it just a tube with some air in it that acts as a spring? Link to comment Share on other sites More sharing options...
joe90 Posted July 10, 2023 Author Share Posted July 10, 2023 1 hour ago, SteamyTea said: Looks similar to the medicine the French Doctor gave me. Is it just a tube with some air in it that acts as a spring? Yes the French love suppositories. https://southendplumbingllc.com/what-you-need-to-know-about-water-hammer-arrestors/ Link to comment Share on other sites More sharing options...
PeterW Posted July 10, 2023 Share Posted July 10, 2023 2 hours ago, joe90 said: Not got around to this but putting this before my boiler was suggested by a plumber friend. https://www.screwfix.com/p/sioux-chief-dw660-2j-water-hammer-arrestor-1-2-bsp/1492r Opinions! not that good if you have very high pressure even though it says good to 250psi. Better to put a 4 litre potable expansion vessel in and it will do the whole system. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 10, 2023 Share Posted July 10, 2023 4 minutes ago, PeterW said: not that good if you have very high pressure even though it says good to 250psi. Better to put a 4 litre potable expansion vessel in and it will do the whole system. +1, and will soften the hammer off the WC's and any 1/4 turn taps which 'slam' shut. At 8bar, you defo need a PRedV on the main as that will be causing all kinds of havoc 'behind the scenes'!! Set it at 4bar and the flow will still be stonking. A 3bar PRedV actually strangles the flow quite a bit, so make sure you can define the set pressure. Remember that you need to have water flowing through the PRedV to set it accurately, so leave a tap on somewhere just running a couple of l/p/m whilst you set it. 2 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 10, 2023 Share Posted July 10, 2023 And then......... "Peckham Spring". 1 Link to comment Share on other sites More sharing options...
joe90 Posted July 11, 2023 Author Share Posted July 11, 2023 7 hours ago, PeterW said: not that good if you have very high pressure even though it says good to 250psi. Better to put a 4 litre potable expansion vessel in and it will do the whole system. 7 hours ago, Nickfromwales said: +1, and will soften the hammer off the WC's and any 1/4 turn taps which 'slam' shut. At 8bar, you defo need a PRedV on the main as that will be causing all kinds of havoc 'behind the scenes'!! Set it at 4bar and the flow will still be stonking. A 3bar PRedV actually strangles the flow quite a bit, so make sure you can define the set pressure. Remember that you need to have water flowing through the PRedV to set it accurately, so leave a tap on somewhere just running a couple of l/p/m whilst you set it. 7 hours ago, Nickfromwales said: And then......... "Peckham Spring". Ok guys, will do, I just wanted to consider all my options. As I often say “every day is a school day” (even at my age 😳). Link to comment Share on other sites More sharing options...
joe90 Posted July 24, 2023 Author Share Posted July 24, 2023 Right chaps, finally got around to moving the PRV to the incoming supply (it was wet on Saturday so indoor jobs a must) even at 2 bar (which I set it too fir the outside tap) shower flow is still very good and no more boiler hiccups and toilet filling quieter. Thanks guys 👍 1 Link to comment Share on other sites More sharing options...
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