Drain and vent revisited

[Arky217]

I have revised my drain/vent sketch as shown. Again, although I'm in an area not subject to code, I would appreciate a plumber's
evaluation to make sure that I'm not making any major mistakes.

Sink #1 is the kitchen sink; #2 is the bath sink.
Of course, the bath sink, commode and tub are in the same room;
they're shown like they are on the sketch just for clarity in how the piping is run.

One thing I'm not sure of is the drain for the kitchen sink. I've read that 42" is the max horz. run before going down and the distance
that I need it to run 66". The dark 2" line down from the kitchen sink is another way that I could run the drain, but I'm
not sure if that is too much drop and might empty the trap when a sinkful of water is drained.

Thanks in advance for your comments,
Arky

[Rob_O]

The 42" you are referring to has to do with venting, the magic number varies with the size of the pipe. Again, I don't have the book handy so I can't tell you what the proper number is for you

Your dark line drain will work fine, but you need to put the top of the trap line below the the bottom of the vent line. Here's a link with some useful pictures... vent goes up and drain goes down and everything works like it should

http://www.familyhandyman.com/DIY-Projects/Plumbing/Kitchen-Plumbing/how-to-plumb-an-island-sink/View-All

[Arky217]

The 42" you are referring to has to do with venting, the magic number varies with the size of the pipe. Again, I don't have the book handy so I can't tell you what the proper number is for you

Your dark line drain will work fine, but you need to put the top of the trap line below the the bottom of the vent line. Here's a link with some useful pictures... vent goes up and drain goes down and everything works like it should

http://www.familyhandyman.com/DIY-Projects/Plumbing/Kitchen-Plumbing/how-to-plumb-an-island-sink/View-All

Thanks Rob_O for your reply, but I'm not understanding exactly what you mean.
Should I forget going the 66" as shown and go with the dark 2" line ?
And if I go with the dark line, should I do it like the island sink link shows and tie the vent into the 3" line downstream of the dark line drain ?

Also, doesn't the island sink arrangement go against the rule of not going horizonal with the vent while below the sink top ?

In other words, if I go straight down with the drain (like the dark line), could I not use a tee instead of an elbow where the dark line starts down, and go horz. from the tee over to the wall vent (the pipe would be hidden within the cabinet) and eliminate the vent going down the wall to the 3" line ?

I guess I'm not seeing the difference in the way the island arrangement vent does and just going horizonal from the trap.

By the way, just why is it not a good idea to go horz. with a vent line until above the sink rim ? Never did understand that rule.

Thanks,
Arky

[Rob_O]

The outlet of the trap needs to be below your horizontal vent line. Elbow down then tee in the trap on the vertical pipe and as long as the drain is flowing properly no water will make its way into the vent line.

Study the picture of the island sink closely and pay attention to the labeling of the vent line. The vent line is above the drain line and the loop is tied to the drain at both ends. This allows any liquid that gets into the vent to go down the drain. Keep the water out of the air and horizontal vents work fine

You can use the dark line to the main, or run two parallel pipes to the wall stack and tee them both in, it will work the same either way. You could even run both the vent and the drain both down to the main, just build a loop so the vent goes up over the outlet of the trap as shown in the island sink picture. The important thing is that the vent line is above the trap outlet and the drain is below the trap outlet so everything flows in the proper direction - vent up, drain down.

That help?

Edit: another option I thought of, run both pipes through the floor from the loop, drain goes straight down into the main and elbow the vent over and tee into the pipe coming down the wall under the floor. Probably the option I would choose