Drains from new kitchen island

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As you can see from the diagram there is a foul drain running underneath a side extension to our home. The man hole on the left is in the garage, the one on the right is outside the back of the house.

The challenge is: How do we connect the drains for the dishwasher and sink on the new island to the drain.

Kitchen Drainage.jpg


I don't want to cut into the main clay drain pipe, especially as it is old, brittle and has been sleeved.

The gully that's internal now, was formally external, has been concreted over, so I am loathed to cut into it.

An obvious candidate for me would be the clay pipe leading from the gully to the main drain. Would that be the place to tee into, take that across to the island, up to the surface and then reduce down to a 40mm pipe (incl. a tee with a cap for drain unblocking) that would have a trap and an inlet for the dishwasher?

ae235


Any advice would be much appreciated here!
 
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Unfortunately with that setup you need to dig.
If the floor is solid you'll need a good grinder.
I would dig out the pipe from old gulley which is concrete over, connect sink and dishwasher and replace it with plastic.
You will need to make sure you overlap the dpm before closing the hole you dig.
On a new installation use mcalpine traps so you won't have leaks any time soon.
 
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Unfortunately with that setup you need to dig.
If the floor is solid you'll need a good grinder.
I would dig out the pipe from old gulley which is concrete over, connect sink and dishwasher and replace it with plastic.
You will need to make sure you overlap the dpm before closing the hole you dig.
On a new installation use mcalpine traps so you won't have leaks any time soon.


Understood. Let's see if there is even any dpm :)
 
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In a recent drain survey the company confirmed the drain is approx. 800mm below the surface and I know it's exact location. So that helps.
 
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Hopefully there is.
How old is the extension?
And was it built under building control?
(Not that it matters much...)

1970's ... so no idea

If there is, would I overlay the existing membrane over the new one I'm placing over the channel/hole I'm digging?
 
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1970's ... so no idea

If there is, would I overlay the existing membrane over the new one I'm placing over the channel/hole I'm digging?
You'll have to overlap it by 4 inches ideally by digging an horizontal line and exposing the original one.
1970s... i suppose you won't find one.
 

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