Drain and vent re-route

[khedrei]

I am looking to do this properly. I don't have any pictures so I will try to explain it the best way I can.

I removed an old vanity in the powder room. The old drain line goes into the side wall. I am replacing the sink with a pedastel sink so I can't have the drain going to the side because it will not be hidden. I need to reroute to the back wall.

Would it be a good idea to try and route it through the wall towards the side and just reconnect it where it is now? Basically the drain would be doing a 180.

I was thinking to just run the drain into the back wall, down to the basement underneath and tie back in to the same pipe, just at a different spot. Nothing else is attached to this drain pipe. Would it be vented properly if I did it this way? Or does the vent have to start where the pipe goes virtical? The run isn't very long, the current drain is right underneath where the sink will be.

The current vent/drain pipe that the drain runs into is in the side wall, runs down into the basement, does a 90 (runs right underneath the sink) then a few feet later runs into a 3" drain with a Y fitting.

Any info would be appreciated.

[leejosepho]

I was thinking to just run the drain into the back wall, down to the basement underneath and tie back in to the same pipe, just at a different spot. Nothing else is attached to this drain pipe. Would it be vented properly if I did it this way? Or does the vent have to start where the pipe goes vertical? The run isn't very long, the current drain is right underneath where the sink will be.

The problem there is that the current drain does not have a vertical drop before going to the pipe in the wall and your proposed change with a long vertical drop could result in the trap being siphoned (since the vent would begin at the new connection point in the basement). As a DIYer who did not have to deal with an inspector, I might work around that siphon possibility by using 2" pipe to do what you are considering ...

... but the pros would likely blast me if I actually suggested that since it would likely never get past an inspector.

[jimbo]

An S trap is not good, neither is a horizontal vent. If you can open the walls, there is probably a way to reroute the drain.

MY commen: beauty is in the eye of the beholder: having the drain "visible" out the side of the pedestal would be OK with me. I do realize that in your sitution, you have to deal with what is OK for your wife!

[khedrei]

To tell you the truth, I don't really like the idea either, but the wife would not stand for it so I don't mind spending the extra bit of money.

I will open the walls and see if I can reroute it.

The current pipe is actually 2" pipe in the wall. I am not sure if the vent is 2" going up to the roof or not. I will find out when I open it. The drain and the trap is 1.5" and the drain into the basement is 2".

Could I use a cheater vent in the back wall? It is a shared wall with the garage. Will there be an issue with the insulation and the air flow?. I don't really like using them, especially when there is a proper vent in place.