D-W-V Pipe sizing

We are installing a new bathroom on the first floor of our house, and want to confirm that we are sizing the drain and vent pipes correctly. We are regulated under UPC 2006.

Starting at the far end, I want to place a toilet on 3" line with 2" vent. About 1' past the toilet a 2" line (5' horizontal run) from a double vanity will join the 3" line. About 6" past that connection a 2" (2' horizontal run) line from a spa tub will join the 3". Finally, about 4' later, a 2" (vented) line from the kitchen (sink with disposer and dishwasher) will join the 3" line. This line eventually increases to 4" when the waste line from the upstairs bathroom joins it.

By my calcs, I'm within the allowable DFU's for the 3" waste line and 2" vent line, and allowable lengths for the fixture arms, but I'd like an expert to confirm for me.

Thanks for a great forum.

Dwv

The numbers are okay, BUT that does not tell us anything about HOW you are going to run the pipes. THAT is almost more important than sizes and distances.

D-W-V Pipe drawing

Thanks hj

Attached is a drawing. All the new DW will be in the crawlspace under the bathroom, with a minimum drop of 1/4" per foot, and installed using proper fittings. Once it joins the existing kitchen drain, I will be replacing the existing 2" with 3" until it meets the main line. This will also give me an opportunity to correct the drain from the kitchen, which was installed with less than 1/4" slope.

Thanks for any advise you can provide.

You need the vent to come up off of the tee for the lavatories. The vent at the end of the run does nothing as far as most codes are concerned. The base of the vent would need to be "washed" by a fixture.

Also, the tub downstream of the toilet off of the main line may be (recently) code compliant but it's usually better to have it come off the lateral to the lavatory.

Dwv

The tub is NOT vented and since you have a "major" fixture, the toilet, flowing past its connection it MUST have its own vent. I assume the lavatories will have a vent going up from the "back to back fixture fitting" you use to connect the two sinks, and a cleanout in the wall below the fitting. The toilet vent is problematical, depending on how you actually do the piping for it.

hj said:

The tub is NOT vented and since you have a "major" fixture, the toilet, flowing past its connection it MUST have its own vent.

Click to expand...

Unfortunately, it is code accepted now in FL and I am assuming IPC since FL is based on IPC. I would agree that there would/should be a better way to do it though. That is if the lavatory is actually vented.

Ipc

My comment was based on the requirements of a "real plumbing code", not the IPC.

I agree with hj I am under the ipc here in Georgia and it is a joke and this is one of the reasons. You are allowed to run a major by a minor, but I hear stories of that not working properly. Stick to the old code it is definitely better in this situation.

OK. I think I understand what you are telling me, I shouldn't run a major by a minor. That's why I came to the experts. Although Nevada is regulated by UPC 2006, I'm less concerned about code and more concerned about it working properly. What was in here before was not vented at all, and never worked well.

I was hoping to avoid a separate vent for the tub, because that drain is in the middle of the room, and is a short distance to the waste line. If necessary, I can route it another direction so that it will pass under a wall and I can install a vent. Based upon what FloridaOrange said, can I install per the revised drawing and connect it to the line from the vanities? Would it be better to run it all the way to that wall and connect it to the vertical line coming down from the vanities/vent (about 85" from the tub drain)?

hj - The drawing on the left shows how I intended to connect the toilet to its vent.

Thanks for all the help.

ddrain

The way you have it drawn, the tub will flow OVER the toilet drain, before connecting to the lavatory drain. That works ONLY if the lavatory drain is raised up so the tub flows into the side of it, and does not drop down to connect to the sink drain.

HJ-I don't understand why the tub drain must join from the side. Can you please explain ? Not contradicting, just trying to learn Thanks

If you run a drop then it becomes unvented.

hj - That is what I meant in the revised drawing. My other thought on that was to take the tub drain all the way to the wall where the lav drain comes down, and connect it to the vertical, below the lavs but above the cleanout and horizontal line. That's about 85", which I believe is still within the allowable limits for a 2" fixture waste arm. It would be closer to take it to the drop from the toilet, which raises a new thought. What if I took each of the waste arms (lavs and tub) to the back wall where the vertical from the toilet drops down. The toilet would be the top, the tub in the middle, and the lavs at the bottom. Then I just have a single vent with all three waste arms connecting to it in the vertical plane before it makes the turn to horizontal. Will that work, or have I recreated the "major past a minor" problem?

Thanks