Maximum vertical drop to/from trap?

[rick1632]

So in my bathroom I'm fitting a new sink - the waste pipe runs along the base of the wall, so I'm trying to connect the sink to a T directly below. The gap is roughly 50cm, less when a waste is fitted to the base of the sink.

I know if I place the trap at the usual distance with a drop after, it could siphon the trap. I thought about using two traps, one under the sink, then the fall, then another at the bottom, but I hear that that's not recommended.

So if instead I just have a steep drop from the sink into the trap - probably around 30cm, would this work?

 

[Madrab]

Nope, overthinking it a bit methinks. A vertical drop from the basin's trap height to the floor is quite a normal height for basin waste runs. You may get gurgling @ the trap when emptying a whole basin full but that could be dealt with by an anti vac trap. What else is on the run?