Fixing My Incorrectly Plumbed Bathroom: Isometric

**CapstanRec** · 09-28-2010, 12:39 PM

hi,

I first want to say that this forum is a great resource. I've been reading the LA plumbing code and this forum off and on for several months.

I'm planning to fix my incorrectly plumbed half bathroom. The existing vent is upstream from the toilet and I have a sanitary T on its back. I know this cannot be done so I'm going to replace it all.

Please take at a look at my attached isometric to see if I have my head wrapped around this conceptually. This plumbing is in the crawlspace under my house. I think I'm going to have to relocate a 1/2" water line to keep the 2" vent as a vertical vent (45 degrees).

Also... one caveat... New Orleans (where I live) has a supplemental code that requires a full size vent. So by code I'm required to have a 3" vent on this toilet. The only way to accomplish this is to run a 3" piece of PVC up the side of my house, which I don't want to do. Louisiana only requires a 2" vent, and this 2" vent is in a 2x6" wall.

Thanks in advance... if this looks ok I'll get some fittings and pipes and get things roughed in.

**CapstanRec** · 09-28-2010, 03:16 PM

Sorry to post again so soon but I went under my girlfriend's house today that was just built in 2009. In the picture attached, it looks like the 3" vent is "horizontal." I thought this was not acceptacle. I know she had a plumbing inspection. But at the same time she had an electrical inspection that passed and some things were missed. The only reason I know is I'm an electrical engineer and am familiar with the NEC.

Thanks again.

**dlarrivee** · 09-28-2010, 07:22 PM

Hope you didn't pay a fortune for that spray foam job.

**CapstanRec** · 09-29-2010, 04:53 AM

I didn't pay for that spray foam job... it's my girlfriend's house. It's open cell and I sure hope it doesn't trap any moisture and ruin her wood floors.

I don't have any insulation under my floors. I did get two quotes and I felt the prices were very high... not to mention neither company would give me a floor replacement if it ruined my floors. My house is 75+ years old with the original heart pine flooring. I couldn't risk it.

Any comment on the plumbing in the picture?

I already realize my first diagram won't work... I'm going to try and get under my house this weekend and get something roughed in. Post back with an actual picture instead of a diagram.

hj · 09-29-2010, 05:46 AM

The only question about the original drawing, other than why you used a black background with red lettering, is what is the purpose of that "dry vent" other than to waste some materials?

**CapstanRec** · 09-29-2010, 06:22 AM

Good point on the coloring... it's just the way my AutoCAD defaults are set up. I adjusted and reattached the same 1st image.

As for the dry vent, the lav drain is only 1-1/2" and wyes into the 3" ... From my understanding, that is a wet vent (which is ok) but it is too small to meet my toilet venting requirements. That why I added the 2" vent. But I'm now thinking I should tie the lav in downstream of the toilet.

hj · 09-29-2010, 06:10 PM

And WHAT is wrong with using 2" for the lavatory drain, regardless of where you connect it? I NEVER use 1 1/2" for any drains. And the 2" dry vent is still just cosmetic and serves absolutely NO purpose.

**CapstanRec** · 09-29-2010, 07:47 PM

Thanks hj, but the 1-1/2" lav drain and 2" vent are all I have to work with. That's just the way it was plumbed. They stick through my floor. The lav vent ties into the 2" vent somewhere in the wall above the lav flood rim and then the 2" extends through the roof. The bathroom itself is already complete and I'm just trying to make the plumbing under the house correct... if that's even possible.

So I guess I'm just really stuck on how to properly vent the toilet. I don't think it's ok to vent it from main stack that services my upstairs bathroom. According to LA code it seemed that the lav drain was ok. Maybe not ideal but ok. I'll stew on a new layout but I am a bit stumped.

On another note, do you have any comments on the photographed I posted? Just curious. How is that horizontal vent ok? If the main sewer starts to back up it seems the 3" vent will fill up because it below the flood rim of the toilet. Thanks again.

**Wally Hays** · 09-30-2010, 03:35 AM

Toilets don't need to be vented. Tear out the 1 1/2 that goes to the lav, increase it to 2" and get rid of the 2" dry vent.

hj · 09-30-2010, 05:59 AM

quote; Toilets don't need to be vented.

That is true, FUNCTIONALLY, but not code wise in most areas. The only time a horizontal vent is appropriate is when it has something, such as a lavatory, connected to it to keep it washed clean, OR which would not drain if the vent were to get obstructed.

**CapstanRec** · 10-01-2010, 08:09 AM

I think I really do understand what you've been telling me for two days now.

I went back and re-read section 911 (Wet Venting) in the LA PLumbing Code:

911.1 Single Bathroom Groups
A single bathroom group of fixtures may be installed with the drain from a back vented lavatory, kitchen sink or combination fixture serving as a wet vent for a bathtub or - shower stall and for the water closet, provided that the wet vent is one pipe size larger than the upper fixture drain but in no case smaller than the lower fixture drain, whichever is the larger, and that both drains conform to Table 908.1.

The idea being if my "wet vent" clogs I'll know it because my lav will back up.

So I need a new 3" drain and from upstream to downstream have a cleanout, 3"x2" combination wye and 1/8" bend to pick up 2" lav drain, then a 3" wye for the toilet tie in and finally a 3" sanitary tee to tie into my main vertical stack. Very simple and straight forward. I also need two 45 degree fittings to offset my lav drain around my 6"x6" sill.

The concept is shown in the picture below... Not exactly my situation, but similar. I think I'll sketch up my actual situation before I put it together.