Is it a violation of code to install a sink drain that passes through a heater plenum? I'm moving my kitchen sink as part of a renovation, and there is a HVAC return plenum made from sheet metal nailed between floor joists where I want to install the drain. I will turn the drainpipe and exit the plenum immediately after penetrating the floor. My alternative is to move the drain about 4 inches forward from the wall, so instead of installing the vertical drain in the wall as normal it will turn vertical in the cabinet under the sink. I have no problem installing the vent line, there is no plenum in that direction.