remodel vent size issue

I am remodeling a powder room on first floor of two story 1925 house. Used to have a pedestal and a toilet on one side and a shower opposite. shower sucked and was not needed, sink and toilet were crowded. Took out all three, and am putting in a large vanity/Lav where the sink and toilet used to be; and putting a new toilet where the shower was. The D and W part of the DWV are pretty easy. Venting, though . . . There is a 2" vent line (easy to use) for the new Lav. There is a nice, straight vertical 1.5" vent that goes up through the roof and down to the crawl space, not 2 horizontal feet from where the new closet flange/toilet will be. I REALLY don't want to change that to 2" -- Very easy to hook up as is, totally a bear, maybe not even possible to change it. So -- can i put in one single toilet with a 3 inch drain and a 1.5 inch vent ?! Is it code and, more importantly, will it work? Thanks in advance.

yes, 1.5" will work. How you connect it is important so you aren't homefree yet.

Whether it meets today's Code depends on where you are; where I am it meets code too, and that is what I have. Compared to the code i have to work under, Code is often stricter in other places.

david

Thank you! But . . . umm, if that is a picture of your house, i think the code there is much more lenient. I am in a fairly large city -- and have seen a few quotes around the net that say "2 inch min. for a toilet vent."
I think connecting it won't be too bad - have lots of room under the floor; probably won't have to do more than 90 degrees total to get over to the vertical vent line.

which code; do you know?

The code i am under is strict about a lot of things; it didn't adopt the latest "large size" venting requirements, so 1.5" vents are acceptable. I'm in a big city too. There are a very small set of differences between my code and the very strictest codes, all having to do with the same question of 1.5"-or-2" diameters, so that is why I felt comfortable responding to your initial post.

Which code are you under; what city are you in?

David

Thanks david - I was referencing your igloo. I am in tacoma, washington -- not sure of the plumbing code.
I was thinking of running a 2 inch line under the floor over to the exisitng two inch vent wall, running up and y-ing in to that existing vertical vent line somewhere above the sink (how far up must it be?) Horiz run would be about 10 feet, then mostly straight up (except for the Y).
seems to me a straight vertical 1.5 inch pipe would let more air in than that circuitous route.
also, what do you think of putting a 2 inch line from the 3 inch line below the floor, up the wall, then reducing to the 1.5 inch line at the ceiling of the first floor -- then i would not have to redo the upper part of the 1.5, but there would be "more air" in the vent than if it was 1.5 the whole way.
p.s. i am not actually getting permits etc., more worried about function than strict code compliance. Thanks for your time and thoughts. JT

A vent, like a drain, should only slope one way. Running it under a floor before you can go up, and certainly if it needs to go down first to get it there, will negate it from qualifying to become a vent. If you can run it up and over...it can join an existing vent if 6" above the flood plane of the highest fixture serviced by that vent - a nominal 42" is sometimes dictated as the "norm" (for a kitchen counter height + 6", though not all counters are at that height).

Draw a diagram, including fittings and shape of fittings. Too many words now, like

rankamateur said:

...running a 2 inch line under the floor over to..., running up and y-ing in to that existing vertical vent line.... also, what do you think of putting a 2 inch line from the 3 inch line below the floor, up the wall, then ...

Click to expand...

JT, what Jim said; only slope one way. And use the right fittings.

Other people will comment after that. I can't comment on the above. Draw a picture, and wait for the experts. There are a few, and they know enough to tell you what you may be missing. The big things to draw are the fittings, the slopes and the distances. Reread that.

Find out what code applies to Tacoma. Some neighbor will know, whether it is IPC or UPC based.

That is all I can do, to help you.

david

Yeah sorry about the description; hard to picture from words. Unfortunately I do not know how to attach a drawing.
We are a UPC jurisdiction = 2 inch vent for toilet. I know the vent must always be going "up", and I can do that. I have a lot of room in the crawl space under the floor of the bathroom to make connections, slope things up etc.

But here is what I think i will do instead:
The existing 1.5 vent is in the wall behind the new toilet location, so is quite close to closet flange. That 1.5 vent extends down into the crawl space, where it is cut off. It also extends straight up, thru the ceiling of the bathroom, into a difficult-to-access attic area, then up through the roof.
I am going to replace the portion of the 1.5 that I can see and access (crawl space to ceiling) with a 2 inch vent. At the ceiling I will reduce the new 2 to the existing 1.5, and not have to mess with the upper portion of the existing vent. It will only be 1.5 at the roof, and for 4 or so feet below the roof. Then it will be 2 inches for about 9 feet going down below the floor, where it will properly Y into the 3 inch toilet drain line. This will give the drain "more air" than it would get if the vent was 1.5 the whole distance. Code? Nope. Will the toilet flush? I think so - there is nothing else on the vent. Please advise if this raises red flags.
Thanks for your time and advice! JT