The sink location is about 5 to 6 feet from a 2" drain/waste/vent pipe that runs directly into the concrete floor and the other end to the roof. Where my father-in-law would like to tie in is about 6 inches off the ground (the pipe comes out of the ground and at about 6 inches runs horizontal away from the sink for about 10 feet before heading up to the roof). So he would like to run it directly from the sink to the d/w/v 5 to 6 feet away without any vents.
pipe and 3 and a half feet for a 1 1/2" pipe. I've also read that the real kicker is that the distance between a vent and a trap should be calculated by the amount of slope in the line. For example a 2" pipe should not be able to drop more than 2" (with a 1/4" slope per foot) before being vented (so a 2" pipe's max distance between trap and vent at 1/4" slope per foot would be 8 foot).
Our slope will be considerably more than 1/4" per foot since we have about 6 feet between the sink and the d/w/v and will be dropping about 2 feet. So our slope is going to be more like 4" per foot. Does this matter? Do I need to look at a different solution, or will this be fine? I don't know if I am just too paranoid about this. I've also seen the check valve as another option, but don't know that I really want to do that? What do you all think?
Thanks in advance, Matt