Underground drainage bottle gully back inlet question

[BathDIY]

Forgive my ignorance...

The old drainage servicing my kitchen (kitchen sink / washing machine / dish washer) is split and needs to be replaced.

As you can see I need to get it out from a concrete path so need to have everything I need to hand as I cannot visit shops at present and I think it will fall apart when I remove it. I have considered digging under the path but again the crack goes down into the existing clay so I think it could all come apart.

Not sure if I need a back inlet gully or not see the drainpipe in the bottom right of the next pic.

Is the gully by the kitchen likely to be part of the existing drainage run from the downpipe in the bottom right of pic?

OR

Is the downpipe likely to go into a system that goes underneath the house in some way?

 

[Hugh Jaleak]

Downpipe is likely to go into its own independent drain, highly unlikely it's connected to the gully, and/or go under the house. Treat the 2 as separate, the gully will connect to the foul drainage, downpipe is likely to go to the Surface water system.

 

[Ian H]

You don’t need a back inlet, a normal gully will sit closer to the wall so be better on that path.

You will likely also need a short length of pipe and an AC4000 type bandseal.

 

[BathDIY]

Thanks for the insight, have ordered what you suggest.

Having done some more research we have a combined system, the house was build 1969.