Do I need a non-return valve between my cold water supply and my dishwasher?

ztkr

Cold water from my kitchen tap has started to taste unpleasant. I think my ageing dishwasher may be to blame, although I can't be certain. I'm about to replace the dishwasher anyway, with a new one (Bosch). My question is, do dishwashers generally have a non-return valve to prevent water from returning to the cold water supply, or should I add one between the cold water supply and the dishwasher?

grumbler

philc27 said:

My question is, do dishwashers generally have a non-return valve to prevent water from returning to the cold water supply, or should I add one between the cold water supply and the dishwasher?

Firstly, you need negative pressure in mains to suck dirty water from dishwasher into mains pipes. Even if this can happen, it can be an extreme situation, not on a regular basis.

Secondly, as the water is only at the very bottom of dishwasher, I think it's very easy to design it to prevent this happening without unreliable non-return valves.

I don't think that you should add a valve, but you can do this if you wish.

Alanp

Look for a wras approved dw, I think they all are ( but not sure with domestic ones) but I’m sure someone will know…

daveyjp

Our Bosch dishwasher is about 4 years old and has a none return valve fitted as standard.

grumbler

daveyjp said:

Our Bosch dishwasher is about 4 years old and has a none return valve fitted as standard.

Do you mean a built-in valve or fitted by the installers?

warwick2001

If its a similar set-up to our Bosch dishwasher, the non-return valve is part of the water inlet pipe i.e. not an additional part

grumbler

warwick2001 said:

If its a similar set-up to our Bosch dishwasher, the non-return valve is part of the water inlet pipe i.e. not an additional part

Are you sure it's a non-return valve, not an 'aquastop' device, protecting a house from water damage, not vice versa?

EssexExile

There is no way for dirty water in a dishwasher to get into the mains supply.

ztkr

I couldn't establish online if my new dishwasher has a non-return valve or not, so I contacted Bosch and they said that water cannot come back through the inlet hose. So, no need for me to fit a non-return valve. Thank you all for your responses.

GDB2222

Of course, this leaves the question of what is wrong with your water supply. 

grumbler

https://www.dwi.gov.uk/consumers/how-to-report-a-problem/