Hello. I have a sink in a 1st floor bedroom  and want to add a toilet. We have bought a sanitop unit. The sink currently has 32mm waste pipes. Is it possible to alter this to a 22mm pipe for the first 5m, then revert it back to the original 32mm pipe for the rest of the drainage away. It will now be draining the new toilets macerated waste and the old sink waste.
It currently goes down into the drain which then connects to the sewer.

The current drainage has gradients and drops which comply with the saniflo instructions and should be ok.
We don't know whether its OK to put the macerated waste in these pipes and whether going via the  drain into the sewer is acceptable.
Thank you