How best to rearrange kitchen sink plumbing

[Northman]

I am putting in a new kitchen, with the sink unit containing drawers rather than the usual cupboard. (I know... but SWMBO...). This is going to necessitate the pipework coming up inside the 42mm service void at the back. The current pipework is forward of this, so will need to move backward. It will be tight for the waste but less of an issue for the water pipes I hope.
The back of the drawer means that pipework coming into the space will need to be higher than approx 410mm. There will be a 1.5 sink wastes to deal with, and a dishwasher to the left of the current pipework. The existing standpipe is ready to take a dishwasher but will need to be in the service void, so will need to be in solvent weld? Or, can I create a standpipe inside the space, with a connection above 410mm?
The two spigots on the exisiting waste piping are not needed, so I hope to simplify the existing Christmas tree of piping a fair bit!
I'd appreciate any thought or comments on the best way of achieving/simplyfying this set up.

Lower left in copper is piping for an outside tap including stop tap and drain valve. and cold feed for dishwasher. That is piped in a combination of plastic and copper -with no clips for support!

 

[blup]

Get a drawer with a cut out for the waste, and space for pipes, otherwise its difficult to see how it will all fit as the waste has to have a route to the back.

 

[Koolpc]

Tell your wife 'NO'.

 

[dilalio]

Usually with this kind of arrangement, it will be a purpose designed sink and carcass with drawers and usually a trap system that is meant to go with it.

As said above, the top drawer has a service space for the waste to fit and wraps round with a horse shoe shape cut out.

Never seen it done any other way and you'll regret not having access when the trap gets blocked.

 

[Northman]

Thanks all. Yes, it is a purpose designed unit with a cut out. Its the dishwasher waste that has me scratching my head a bit, particularly how high up it can connect into the sink waste? Would it be ok to direct that straight to the waste separately to the sink, rather than bringing it into the unit?

 

[dilalio]

Thanks all. Yes, it is a purpose designed unit with a cut out. Its the dishwasher waste that has me scratching my head a bit, particularly how high up it can connect into the sink waste? Would it be ok to direct that straight to the waste separately to the sink, rather than bringing it into the unit?

View attachment 365724

If you can, it's best for dishwasher to have it's own connection to the waste pipe - or even it's own waste pipe to gully or soil stack.

When connected via an appliance spigot, to the sink waste, you'll always hear gurgling from the sink as dishwasher discharges.

However, it can go on to a spigot and just go from the centre back of the unit... Just swing spigot round to point that way.

 

[dilalio]

If you can, it's best for dishwasher to have it's own connection to the waste pipe - or even it's own waste pipe to gully or soil stack.

When connected via an appliance spigot, to the sink waste, you'll always hear gurgling from the sink as dishwasher discharges.

However, it can go on to a spigot and just go from the centre back of the unit... Just swing spigot round to point that way.

Any appliance connected direct to waste will need it's own upstand kit though... To provide a water trap to prevent smells from sewer backing up through machine.

 

[Northman]

Thank you! I've been over complicating this in my head, and you've helped immensely. I just move the waste back a bit (solvent weld) and bring it up the service void then through the back of the unit at a suitable height to clear the drawer and be able to take the sink connections and dishwasher onto a spigot. The copper/plastic I'll re-route to the void, probably T off lower for the outside tap pipe and have the drain/stop tap accessed under the units from the plinth. (Probably do it all in copper and clip it properly!).
I could make a separate connection (with trap) for the dishwasher, but its right next to the sink, so I think the above is the optimum path.

 

[dilalio]

probably T off lower for the outside tap

Don't forget this needs a NRV and isolator for turning off internally, during winter!

have the drain/stop tap accessed under the units from the plinth.

As long as there's enough access to change it if it fails!

Worth considering now, rather than having to dismantle/smash kitchen units in an emergency, as I often have to!