My washing machine waste is currently connected to the sink waste & trap via an extended pipe which seems a bit daft as the main waste pipe runs behind the w/machine, can I put the sink on a normal P trap & add a U bend or P trap & T connection halfway along the run (behind the w/machine) with a short length of pipe coming out of the top of the T connection to form a stand pipe? The proposed set up effectively means the sink will have to drain through 2 P traps, I'll keep the same gradient on the waste pipe but will this work/be ok?