Water hammer in cold supply

Hi,

Have a really annoying problem with a noise in the cold supply. It is just a loud single bang which occurs when either the downstairs toilet is flushed, or when the washing machine or dishwasher are being used.

I can get rid of the problem when I restrict the flow of water through the cold supply stop cock, but this then reduces the water pressure in our shower as we have a combination boiler - so no cold water tanks in the loft or anything like that - just everything fed from the mains.

The toilet, the washing machine and dishwasher all have isolater valves and I have tried to restrict the flow of water by closing those of partially. However this then has the effect of making a loud rushing noise for the water for the pipes which lasts for the whole time that the toilet etc is filling up.

Having searched the forums it seems to be suggested that a pressure reducing valve or a shock arrester could cure this problem. If so do I need to place one on the supply to every item which causes the loud bang.

Thanks for any input.

srj321

suggested that a pressure reducing valve or a shock arrester could cure this problem. If so do I need to place one on the supply to every item which causes the loud bang.

Click to expand...

Just one of either or both should suffice.

ie. 1 pressure reducing valve AND / OR 1 shock arrester

I used a shock arrester from Toolstation does the trick brilliantly..I think it needs to be within 2m of an/the appliance(s)

Thanks for the replies - bit confused now though.

2 things spring to mind. 1st thing, don't know if this is a dumb question, but out of interest what exactly does a pressure reducing valve do which just closing the stop cock slightly doesn't do.

2nd thing if the shock arrestor has to be within 2m of the appliance then this suggests I need 3 of them for each of the things which causes the loud bang.

Thanks.


srj321

Hi a shock arrester stops the shockwaves which travel back along the pipe when the supply is turned off, if you were to install one seeing as you seem to have the same water hammer from different sources i would suggest you install one just after your main stopcock, it would be an idea to investigate the main stopcock for a loose jumper.
If you can turn off your water supply outside your house so that you can remove the head of your main stopcock, the jumper is the round part inside which has the washer on held in place with a small nut and a spindle which goes up inside the part of the stopcock that screws done,if it is a fairly loose fit this can cause your type of water hammer, you could possibly check this out by standing by the stopcock and get someone to turn on your cold kitchen sink tap and then turning off fast.