Shower needs a 40mm waste, a 32mm may not handle the flow, especially as it bungs up with soap, hair, etc. I would also personally run the entire waste from the macerator in new, solvent welded pipework, to avoid any risk of problems further down the line. However, that is your choice.
I would not though connect any gravity discharge to the pumped discharge pipework from the macerator, even with a NRV I think you are asking for trouble. If the pipework blocks, then it's going to look for an alternative way out, and the result may not be pretty. If you must have a macerator, go for one with the additional connections for wastes, and pump the lot.
I would not though connect any gravity discharge to the pumped discharge pipework from the macerator, even with a NRV I think you are asking for trouble. If the pipework blocks, then it's going to look for an alternative way out, and the result may not be pretty. If you must have a macerator, go for one with the additional connections for wastes, and pump the lot.