Dishwasher - New Cold Water Supply

[hedgehog144]

I'm hoping to fit a new dishwasher this week and looking underneath the sink (images attached) think I'll need to add a new connection to the cold water supply.

Can anyone advise the easiest way to do this? I've seen lots of posts about splitting supply where there is a washing machine already in but think this will need to be a totally new supply?

At the moment I am thinking of adding a tee off to the side between the current isolation valve / flex hose and main supply, then off that tee having a check valve then a dishwasher connection with isolator after that? I assume I need short runs of 15mm pipe to join those bits together?

Thanks.

 

[hedgehog144]

Apologies, image rotated 90 degrees

 

[endecotp]

(What do you mean by “check valve”? If you mean non-return valve, why do you think you need one?)

Simplest option:

https://www.screwfix.com/p/jg-speedfit-plastic-push-fit-adapting-appliance-tap-tee-15mm-x-15mm-x-3-4-/27471

Next simplest:

https://www.screwfix.com/p/pegler-compression-washing-machine-valve-tee-15mm-x-15mm-x-3-4-/76344

 

[hedgehog144]

Thanks for your reply.

I had read online, a "how to install a dishwasher" page and other forum posts, that a non-return valve (also seems to be called a double check valve e.g. Flomasta Double Check Valve) should be fitted to the cold water supply to prevent backflow of dirty water from the machine into the fresh water supply. Reading again it looks like that isn't clear-cut as the machine should have this protection built in but some advise installing the valve anyway in case an older machine or something else is installed on that pipe in the future.

Thanks for linking the tee valves. I'd rather use the brass fitting as I've seen some forum users feel the speedfit ones can leak over time. I assume one of those tees just needs to go between the main supply (horizontal pipe in my picture when orientated correctly).and the isolator which is currently attached to the flexi hose for the cold tap? With short lengths of copper pipe between the relevant bits for the compression fittings to go onto?

 

[endecotp]

I had read online, a "how to install a dishwasher" page and other forum posts, that a non-return valve (also seems to be called a double check valve e.g. Flomasta Double Check Valve) should be fitted to the cold water supply to prevent backflow of dirty water from the machine into the fresh water supply.

Let’s see if anyone else comments on that. I don’t believe it’s common to fit non-return valves in dishwasher or washing machine supplies.

Thanks for linking the tee valves. I'd rather use the brass fitting as I've seen some forum users feel the speedfit ones can leak over time. I assume one of those tees just needs to go between the main supply (horizontal pipe in my picture when orientated correctly).and the isolator which is currently attached to the flexi hose for the cold tap? With short lengths of copper pipe between the relevant bits for the compression fittings to go onto?

Yes; you can just chop a short bit out of the pipe and insert the tee.

 

[hedgehog144]

Ideal, thanks for confirming!

 

[CountryFan]

See here for water regulations advise. I'd say most come with an air gap which satisfies the regs, but obviously not all do and a lot is to do with the hoses being used. Good to know you take the regs seriously, I've seen a lot of illegal installations in domestic properties, which a lot don't seem to think the regs apply to them or in most cases are ignorant to them. What people don't know is they can be prosecuted from the water undertaker as well as the installer.

 

[hedgehog144]

Thanks for the additional info CountryFan. I'll put a double check valve in the pipework just before the dishwasher valve. Happy to spend a fiver for my own peace of mind that the protection will be there.

Assuming all goes well I'll have a 15mm equal tee with bottom connection to the supply, top to isolator / flex hose / cold tap, and side tee to double check valve / dishwasher valve.