Adding a dishwasher to washing machine plumbing

[DIY10291]

I would like to add a dishwasher to the kitchen for the first time.

I can't put it near the sink without removing cupboards, but there is space next to the washing machine. Are there any obvious problems with this choice of placement?

I am hoping it is an easy job to use the existing water supply and standpipe (pictured). Is this right?

Cold water feed
Can I simply turn off the water supply, remove the existing valve with a spanner, and fit https://www.screwfix.com/p/bsp-compression-appliance-tee-brass-x-x-15mm/24030 to the existing 15mm copper cold feed using a brass olive? Then would the washing machine and dishwasher inlet hoses simply screw on to the tee?

Waste
I am less clear on how the drain hoses should be plumbed.
Can I remove the washing machine drain hose from the standpipe, then fit one of https://www.screwfix.com/p/mcalpine-twin-hose-connector-40mm/206HR to the top of the standpipe? Is it possible my standpipe isn't 40mm, or are they all that size? How would this piece fit to the standpipe, since there is no connector at the top of the standpipe? Would the height of the standpipe need to be adjusted? How do the drain hoses of the two appliances fit onto the twin hose connector? Do you set a particular angle of the swivel nozzles on this connector, or is it just flexible? Will the existing standpipe and drain be able to handle the new appliance, if both are being used at once, without risk of overflow? Does the air beak eliminate the risk of backflow?

Thanks very much

[GALLERY=media, 107802]275418651_1714806512244510_3141920079559283990_n by SK10291 posted 13 Mar 2022 at 7:00 PM[/GALLERY][GALLERY=media, 107801]275629290_656993615521877_7193687054366474612_n by SK10291 posted 13 Mar 2022 at 7:00 PM[/GALLERY][GALLERY=media, 107800]275444582_337721284968025_1102306750984095083_n by SK10291 posted 13 Mar 2022 at 7:00 PM[/GALLERY]

 

[Burnerman]

Your proposal for the water feed is fine, but obviously if one machine requires repair or whatever then both will have the water supply interrupted.....not a real issue in real life.
Likewise the waste water proposal is ok, the stand pipe, which will almost certainly be 40mm can handle both machines pumping the waste water out at the same time.
Keep the stand pipe high, just below the top of the machines to prevent syphoning.
John

 

[DIY10291]

Your proposal for the water feed is fine, but obviously if one machine requires repair or whatever then both will have the water supply interrupted.....not a real issue in real life.
Likewise the waste water proposal is ok, the stand pipe, which will almost certainly be 40mm can handle both machines pumping the waste water out at the same time.
Keep the stand pipe high, just below the top of the machines to prevent syphoning.
John

Thanks! So if the standpipe is currently the correct height, will I need to shorten it by the height of the twin hose attachment, or will it be fine without? Would I just use scissors for that?

Does the twin hose connector connect to the standpipe via compression fitting? Do I need a jointing compound for either this seal or the cold feed one? Finally, how do the drain hoses fit to the twin hose connector? Thanks again

 

[denso13]

or will it be fine without

Fine without, if there is room for the connector. Use a junior hacksaw to shorten it if required.

Does the twin hose connector connect to the standpipe via compression fitting?

Yes

Do I need a jointing compound for either this seal or the cold feed one?

No

Finally, how do the drain hoses fit to the twin hose connector?

Just push fit. You could use a jubilee clip for peace of mind but not normally required.

 

[DIY10291]

More questions:

1) There is a vacant hot water connection next to the cold water one. What would happen if I used this instead of teeing off the cold? Do dishwashers finish their cycles with cold rinses to remove the soap, which would then waste a lot of hot water? And what if the hot water tank/pipes are dirty - might this be no good for a dishwasher?

2) Does the dishwasher need to be attached to the worktop?

3) The dishwasher will be replacing a freezer - for the electrical connection, can I just plug it into the extension lead the freezer was using? (Does it even come with a standard plug?)

Thanks!

 

[Burnerman]

Your dishwasher will be designed to use a high pressure, cold water fill and may object to a low pressure supply - either hot or cold.
There’s no need to connect it to the worktop underside.
It will come with a standard 3 pin plug.....use an extension that will deal with its requirements but don’t use a coiled one!
John