Water knock / shock

[Loofah]

I have some water shock in the system somewhere which is mainly set off by the dishwasher; sometimes the washing machine and 1/4 turn taps although not as much.
I have an unvented system with this fitted which has the PRV integrated-

I'm a bit (but not completely) clueless on this set up so wondered what info you need from me to help in removing the water shock? Is it as simple as reducing the PRV? I haven't seen anything fitted to the integrated dishwasher that resembles a sock arrester

 

[Loofah]

I can always just lob one of these on the dishwasher supply and hope for the best?

Sioux Chief DW660-H Water Hammer Arrestor 3/4" BSP Connection - Screwfix

Order online at Screwfix.com. Professional water hammer arrestor that quietens noisy and banging pipes and reduces stress on pipework. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

 

[RandomGrinch]

I can always just lob one of these on the dishwasher supply and hope for the best?

Sioux Chief DW660-H Water Hammer Arrestor 3/4" BSP Connection - Screwfix

Order online at Screwfix.com. Professional water hammer arrestor that quietens noisy and banging pipes and reduces stress on pipework. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

I've fitted one to my washer dryer.
It worked well, but needed an extra washer to fit on the back of the machine, without leaking.
However, after a while, the hammer came back.
I found, reducing the flow by semi-closing the isolator (In combination with the arrestor), gave the best result.
Playing with the isolator is something free to try first!

 

[Loofah]

Why didn't I think of that?! Good call I'll give it a shot

 

[Madrab]

Find the loose/close pipework and secure it, could also be a freebie

 

[Loofah]

Find the loose/close pipework and secure it, could also be a freebie

Annoyingly the pipework is pretty solid. I've secured where I can get to but this is really just noise in the pipes rather than movement or if it is movement it's buried in the guts if the house!

 

[Madrab]

Annoyingly the pipework is pretty solid. I've secured where I can get to but this is really just noise in the pipes rather than movement or if it is movement it's buried in the guts if the house!

The pipes don't make a noise on their own, if you see what I mean. Water hammer, usually where water pressure is quite high and fast closing valve are used, is a compression pulse that's sent down the pipework when the valve closes quickly and the water stops suddenly. That pulse doesn't actually make the sound, that's usually when it finds an area where the pipes are loose or close together, then the pipes move and 'knock'

If you can't get to it all then fair enough and an arrestor is the alternative. Don't touch the unvented combination valve as that's not a DIY'able job

 

[Loofah]

Yes, I did a quick read about unvented systems and stopped there!
Can you fit a system wide arrestor or are they per appliance?

 

[Madrab]

You can fit system wide arrestors but that may not cure it, it will only cure it if the arrester can intercept the shockwave before it gets to the section that is knocking. Localised is better as it intercepts the shockwave before it can get anywhere.

 

[Loofah]

Makes sense, thanks