Guidance required for completing my laundry room waste

[Vhans]

It seems as though I've been fixing up my builders mistakes all summer, but am finally onto the last room (laundry room). Need some guidance on the drainage please.

I have 2 50mm black waste pipes sticking out of the ground in the corner. Both apparently feed into a 100mm black pipe which goes out to the sewer. My intention is to ideally cap one off and then have the other linked up to the sink waste, approx 1metre away, into which the washing machine would also drain into.

So I popped to B&Q hoping to find some fixings that would allow me to reduce the 50mm black pipe down to 40mm, then connect to standard white drainage pipe. This would then be fed from the sink, into which the boiler condensate, washing machine, and sink waste would drain.

Can I just check that reducing the 50mm to 40mmis correct? Also, is this all push type fit, or do I need to use some sort of adhesive? Also, am assuming because the black pipe is coming straight up from a 100mm pipe that is servicing the sewer, I need to put some form of u bend to mask odours?

Sorry, I'm sure this must seem to be a really basic and obvious question to a pro or an reasonable amateur. Appreciate any help and advice. Thanks.

 

[PrenticeBoyofDerry]

You will require traps to prevent unwanted odours, you can purchase sink waste traps that also have a position(s) for other appliances to be connected.
If the transition joint between 50mm-40mm is easily accessible, then push fit can be used. If not I would suggest solvent welded joint, this would require solvent weld adhesive and waste pipes and fitting that cab be used for this technique, as they are not the same as the push fit waste pipe/fittings.