Bosch dishwasher water hammer - valve already replaced

[copea]

Good afternoon,

I have a Bosch SGS56E02GB/45 dishwasher which has recently started causing a hammering in the pipework when it fills.
The needle on the pressure gauge on the rising main jumps up and down in time with the noise.

I replaced the fill valve, but this has not solved the problem.
I then read that the impeller jug failing could also cause the same symptoms, so I bought one of those only to find my dishwasher doesn't have one, despite it being advertised as compatible (rookie error - should have opened it up first).

There haven't been any other changes in the plumbing in the house before/since the problem started, and there's a PRV on the supply limiting it to 3 bar.

Any ideas what I could try next please?

Thanks for any pointers.

 

[copea]

Not sure why this was moved from appliances into plumbing and central heating, as it's clearly an appliance issue...

Anyway, I've resolved it:

The float in the pressure chamber which registers the water level in the sump was not sinking to the bottom of the chamber when the machine emptied due to an accumulation of residue.
The motion of the water entering on the fill cycle was causing the float to rock/bounce, and as it was at the top of it's range, it kept triggering the 'over-fill' switch with every bounce.

What I was actually hearing was a combination of the fill valve shutting off and the drain pump kicking in for a split second as the machine believed it was over-filling.

I took the pressure chamber apart and cleaned it out, and the problem has gone.

If I'd have taken the left side panel off and watched what was happening when the noise was being made, I'd have diagnosed it a lot sooner!

Hopefully this helps someone in the future.

 

[jj4091]

Probably because "water hammer" is a plumbing term & issue, not "clearly" an appliance one.