Office block coffee station dilemma

[Rybo_1]

First fixed a coffee station at an office recently. All to drawings all happy days. Just a Cold feed under a raised floor and a pumped waste feed which went under the floor below the units, due to integrated dishwasher and a fridge and then up the wall to a 1000mm high and then through wall and across to nearest soil.

Turned up today to second fix and planned and then they've added a new hand basin in the corner. No one's told me. Obviously not happy. Anyway. It's a client request can I sort it. The cold feed no problem under raised floor and up but the waste, a whole nother issue. They said can't you just tee into the pumped waste and place a check valve to stop it pumping back up basin waste. I really don't think this would be a sign of good workmanship. Almost relying on the fact that the pump will be used often to push excess water away. Could/would this work. They're almost insisting on it.

Also, could I install a second pump (sanivite) and join in to the existing pumped run or is that asking to much from a 1 1/4 pipe which at this stage can't be altered and I can't install a new run direct to soil.

Another thing.is that I can't run gravity to other sani due to appliances