Guys, thanks for all your contributions so far. I will go back round to the flat next week to see if I can work out why the pipes weren't taken outside in the first place.
Bearing in mind that all this is going on under the kitchen sink, would the following arrangement be 'legal'? PRV to be connected to 40mm waste pipework via a tundish; condensate pipe tees into this same 40mm pipe lower down (below tundish); then a trap before this pipe joins up with the 40mm pipework from the sink (i.e. this last tee would be after the kitchen sink trap.
Would that be acceptable?
Bearing in mind that all this is going on under the kitchen sink, would the following arrangement be 'legal'? PRV to be connected to 40mm waste pipework via a tundish; condensate pipe tees into this same 40mm pipe lower down (below tundish); then a trap before this pipe joins up with the 40mm pipework from the sink (i.e. this last tee would be after the kitchen sink trap.
Would that be acceptable?