Noisy PRV with washing machine and dishwasher

[Darren Scott]

Morning all,
Wonder if someone can help me at all. Got a high pressure system with a PRV fitted in the loft just before the tank feed, also providing the balanced cold. Now when the washing machine is filling (typically early hours in the morning on a timer) or when the dishwasher is filling (yep you guessed it, just as we go to bed) there is a really loud banging noise (bit like water hammer but more of a single thud). The 'thud' happens when the fill is stopped, for instance the washing machine fills on and off early in the cycle, we hear the water fill, then 'thud' as the fill stops... fill stats again as per the cycle and then 'thud' when it stops. Same with the dishwasher. Been happening for ages and it wakes us up in the morning or keeps us awake at night. Was up in the loft today when the Mrs put a wash on, coincidentally I was standing right next to the PRV when it happened. Bingo, this is where the noise is coming from, but I have no idea why? Some pictures attached.
thanks for any advice you might be able to offer me.
Darren.

 

[Knappers]

Sounds like waterhammer.
Some appliances have shock arrestors built in but you can also buy them to fit in the pipe.
If it happens with particular appliances then one should be fitted near the offending article.

 

[Knappers]

Worth checking the precharge on pottable expansion vessel too

 

[green grant]

so at the time when the localised water pressure is going to be at it's highest, you get water hammer from increased pressure...mmmmm LOL. It is what it is. You can also test this bizarre theory of mine by switching the washing machine on at different times and see what happens.

 

[Knappers]

so at the time when the localised water pressure is going to be at it's highest, you get water hammer from increased pressure...mmmmm LOL. It is what it is. You can also test this bizarre theory of mine by switching the washing machine on at different times and see what happens.

Whats your point?

 

[green grant]

Whats your point?

I'm old school, O levels, A levels, University, undergrad, postgrad, MEng so please excuse my ignorance at not having an NVQ2. It rains, you get wet, its frosty, you get cold. Its what it is. Live with it. Its not 24/7 is it. Is my house going to explode because of this nose? NO, of course not. Is it going to damage equipment? NO. So my point is either live with the minor inconvenience or change the time you wash so you don't notice it. Its a very first world problem, so my point is also perspective

 

[Knappers]

OK, well at least you made a point that time!
I'm not even going to bother with a rebuttal but your clearly not very smart (especially considering how well educated you claim to be).
Anyway I'm off for a walk in the rain, I will be wearing my waterproof coat as I don't want to get sick, nor do I feel that I require perspective.
I hope the river under your bridge doesn't flood.

 

[green grant]

OK, well at least you made a point that time!
I'm not even going to bother with a rebuttal but your clearly not very smart (especially considering how well educated you claim to be).
Anyway I'm off for a walk in the rain, I will be wearing my waterproof coat as I don't want to get sick, nor do I feel that I require perspective.
I hope the river under your bridge doesn't flood.

see, you can resolve probelms..wear a coat...simple when you apply logic

 

[ShaunCorbs]

Try this op

https://www.NoLinkingToThis/p/sioux-chief-dw660-h-water-hammer-arrestor-bsp-connection/9813r

 

[Darren Scott]

Thanks to Knappers and ShaunCorbs that responded with sensible replies. I have fitted two of the Sioux Chief arrestors close to the dishwasher and washing machine and that has helped enormously. No need to change the time we put the washing machine on or the dishwasher now ;-)

There is still a tiny bit of noise in the loft but only tiny so will check later how to check the pre charge on the expansion vessel too. Thanks again both of you for your helpful advice.
Darren

 

[Knappers]

Your welcome Darren,
Assuming you have a pottable vessel, it's usually white, sometimes silver and plumbed in to cylinder cold feed after control valve.
•Connect a tyre pressure gauge to schrader (tyre) valve and check the pressure for reference.
•Isolate cold supply to cylinder and open hot tap
•with tyre pump, pump vessel back up to reference pressure (or very slightly below)
•remove pump and check valve not leaking air (spit on finger)
•turn off tap and turn on cold supply