Pipe Knocking During Dishwasher Cycle - Water Hammer

[jamieellis888]

Hello,

I have spent ages looking on the internet to try and find a solution to this issue, and I apologise in advance as I know similar questions have been asked about this topic on here several times, but I would like to explain my specific issue with the hope someone might be able to come up with a solution.

About 18 months ago, I bought a house and had a complete new heating system (combi boiler), and re-pipe done, I also had a dishwasher installed in the kitchen. However, an issue has developed in the last 6 months where during certain parts of the dishwasher cycle, a knocking noise can be heard somewhere in the house, usually one after the other for 10-12 seconds, but usually at least a couple of times during a cycle. Now despite running around the house like a tit trying to pinpoint the noise, as it only does it for a short period, I haven't been able to pinpoint exactly where it's coming from.

After putting up with it for a couple of months, I started looking for answers on the internet and came across "water hammer" which seemed to fit what was happening. I subsequently bought a water hammer arrestor and fitted it in between where the dishwasher water feed connects to the copper pipe under the sink, but it has made no difference.

I have looked for hours to try and find an answer, but depending where you look, the answers just seem to contradict themselves - some say air in the system, some say not etc..... My issue is pulling the floor up (and in some cases the pipes are channelled into the wall), isn't really an option, but I am concerned that if this is ignored it could become a bigger issue - not to mention that it is a pain in the backside!!

Any suggestions would be greatly appreciated.

Thanks in advance,
Jamie

 

[AWheating]

expansion noise from the waste being dumped?

 

[WHPES]

Sounds to me that there are inadequate pipe brackets on the pipework causing it to shake around.

A quick solution may be a Sioux water hammer arrestor

 

[jamieellis888]

Thanks for the couple of replies.

"Expansion noise from the waste being dumped" - Presumably this would mean the noise would be heard right by the dishwasher? If so, this is not the case as it's somewhere else in the house.

I am thinking you may be right about the inadequate pipe brackets, but given that the whole house was re-plastered and decorated and a complete new floor installed upstairs only 18 months ago, I don't really fancy making holes in my walls and/or ripping the floor up - not to mention the fact that I still haven't been able to pinpoint the noise 100% as it's difficult to replicate.

As I mentioned in my original post, I have tried a Sioux water hammer arrestor, but htis has made no difference whatsoever......

Any other suggestions?

Thanks,
Jamie.

 

[Frenchey]

It could be a loose jumper in the incoming stopcock

 

[jamieellis888]

Mmmmm, "loose jumper in the incoming stopcock" is interesting and not something I've read about before, sorry to ask a stupid question but is there anyway I could confirm that with replacing the main stopcock?

 

[Frenchey]

Mmmmm, "loose jumper in the incoming stopcock" is interesting and not something I've read about before, sorry to ask a stupid question but is there anyway I could confirm that with replacing the main stopcock?

When the solenoid in the dishwasher shuts down after the required amount of water is let in ,this can send a shockwave through the system that will cause the jumper to hammer .


If the hammer occurs at the same point in the dishwashers cycle, listen the stopcock.



Or or just replace it ,

 

[turnpin]

Agree with the loose jumper theory how high is your mains pressure at the kitchen sink ..may need a pressure reducing valve regards Turnpin