The trap should be before the vent. The trap is used to maintain a watter barrier to prevent waste water and sewer gasses from entering the home. The vent is use after the trap to allow the water to flow freely in the pipe with out drawing the water from the trap.
The condensate drain on the a-coil should have a trap and the trap should be vented for proper operation . The vent should rise above the top edge of the drain pan in the unit. Their should be a capped clean out before the vent.
An S trap would go through the floor. A P trap goes through the wall. As long as the drain is below the bottom of the sink, it should drain. Distance between the bottom of the sink, the trap and the drain does not matter, it just changes how much water stay in the drain. Normally it is just in the trap, but it can be above the trap if circumstances cause the trap to be lower than usual.
To prevent clogs in your heat pump condensation drain, regularly clean the drain line with a mixture of vinegar and water, install a drain line trap to catch debris, and schedule annual maintenance checks with a professional HVAC technician.
2 in.
They can also require to have a self primming trap
Two inches
The difference between a gully trap drain and a floor drain is placement. A floor drain is in a floor, a gully trap drain goes on an external wall.
An S trap is not allowed in a plumbing system. Only a P-Trap
If you have a floor drain, there is a trap on the bottom of that. The main line shouldn't have a trap in it. There does not need to be one on the main because each fixture should have one and that's just another place for a clog to form.
It may be sitting in the trap which should be located directly below the drain.
......before, but I would not recommend direct drain. The washing machine hose must extend up above the flood rim of the washing machine before entering the drain. If not, there is a possibility of sewage backing up into your washing machine.
A frost proof toilet the trap is located below the frost line