Trying to install basement sink
Hey, guys. I'm trying to install a basement sink, but the waste pipe is about four feet off of the ground. Looking at the article here
I can solve the problem by hooking up the sink as normal, but have it drain to a sump box/pump combo. I'm a little confused, however. There are two drains out of the box, one for the actual water and one going to the "vent stack", as the article mentions. Why do I need the second pipe coming out of the box? Shouldn't all of the exhaust gases leave the box through the drain coming out of the box on the left? Is it because there's a check valve on the left to make sure water doesn't flow back into the box?
If my assumptions are right, is the waste stack and waste pipe the same thing? If so, I would cut into my pvc waste pipe and have the pipe on the right (coming out of the sump box) go to it. I was then planning on having the pipe on the left drain into the existing drain for the washing machine.
Does this sound correct? Any help would be greatly appreciated.