68mm / 40mm waste pipe ?

[dal5band]

My son's house has an open kitchen drain outside - the type with a grating and a trap. Feeding into it (back inlet) is a 68mm down pipe with various smaller pipes feeding into it - the bath, the wash basin, the kitchen sink and the washing machine. All the connections are just 40mm pipe sitting inside a 68mm pipe on various angled T branches.

What's the best way to tidy this lot ? can you get a 40mm to 68 fitting? or do we need to change the down pipe to something else?

 

[JPC]

68mm is for rain water and should not have all the waste water pipes connected to it. your basin/bath etc water should be connected to 110mm soil pipe (where hopefully your toilet is connected to).

in some old properties the drains are shared and rain water goes to the sewers but still.

is the 110mm pipe nearby ? any pics we could have a look at

 

[dal5band]

It's not related to the rainwater drain which is separate.
It is an old property where the kitchen drain had a back-inlet with a "hopper" for the ist floor drains. The cast iron hopper and down pipe have long gone but someone has installed a rainwater down pipe in the past.
(Connecting to the 110mm is not an option - it is in fact a 3.5" cast iron and to replace that with plastic is not a small job).