The UPC mentions the aggregate cross sectional area of all vent must be equal to or greater than the main drain. With a one story house that has a washer 11/2 vent and a kichen sink 1 1/2 vent and a bathroom group that would be wet vented with a 2 " vent for the lav. my addition gives me a toal of 6.66 " were a 3' vent is 7.06. So would I need to increase the size of one of the vents. Also when the vents are combined in the attic wouldn't the main vent have to be 3' going through the roof.

Guess you can't edit the spelling for the header question. Sorry "VENT"

Thanks

We have several UPC plumbers on tap that can answer your question. In my area, (SPC) we are mandated to install one three inch vent on a single family home. We usually place this on the kitchen where we continue on with three inch to the main.
We do it this way because so many washers are tied to the same line and with garbage and grease from the disposal added to the lint and fiber from the washer a two inch drain is just too small. Good luck, Tom

UPC doesn't not allow wet venting. Your conflict in totals arises from wet venting your bathroom group. Each fixture has to have its own vent. Once you install all vents as required by the Code, your numbers will add up.

SIZE RULE:

If you are under the IRC (International Residential Code) all structures are required to have one "Main Vent" which must run undiminished in size from the "Main Drain" through the roof. After that is achieved any additional auxiliary vents may be reduced to 1/2 the diameter of the line they serve but not less than 1-1/4".

I.E. If you are under the IRC and you are installing an auxiliary vent on a 3" line, the vent line may be 1-1/2".

However, under the UPC (Uniform Plumbing Code) to size a vent line you must first determine the total DFU (Drainage Fixture Units) load of all the fixtures served by that vent line, then consult UPC Table T7-5 to determine the size of line required for the vent.

Under the UPC ALL VENTS must terminate through the roof.

UPC Table T-7-5 Vent Sizing Table

Maximum number of DFU's / Minimum vent size
Max.1 dfu/1-1/4"
Max.8 dfu's/1-1/2"..(no water closets)
Max.24 dfu's/ 2"
Max. 48dfu's / 2-1/2"
Max. 84 dfu's / 3"
Max. 256 dfu's /4"

Under the UPC you are not required to have a Main vent, however the combined aggregate cross sectional area of all vents must be equal to or greater than the cross sectional area of the house main drain.

UPC doesn't not allow wet venting. Your conflict in totals arises from wet venting your bathroom group. Each fixture has to have its own vent. Once you install all vents as required by the Code, your numbers will add up. In point of fact Milo. UPC does,indeed, allow wet vents.

UPC 97 edition
908.1 Wet venting is limited to vertical drainage piping receiving the discharge from the trap arm of one (1) and two (2) fixture unit fixtures that also serves as a vent for not to exceed four (4) fixtures. All wet vented fixtures shall be within the same story; provided, further, that fixtures with a continuous vent discharging into a wet vent shall be within the same story as the wet vented fixtures. No wet vent shall exceed six (6) feet in developed length.

908.2 The vertical piping between any two (2) consecutive inlet levels shall be considered a wet vented section Each wet vented section shall be a minimum waste pipe size of the upper fixture or shall be one (1) pipe size larger than the required minimum pipe size for the sum of the fixture units served by such wet vented section, whichever is larger, but in no case less than two (2) inches.

So there are cases where wet vents are allowed in UPC land. What's next? High loops .on a dishwasher? ( gasp! ). Cheers, Tom

Thank you Tom for pointing it out to us.. .

I believe this provision is made to accommodate remodels with such installations so Cities don't force Homeowners to rework their entire plumbing system during remodelings. When we work on such remodels, we are allowed to repair, or replace - but no to add. If you happen to add new fixture to the existing system, we have to go through the roof. In new construction, including additions, we would not pass our inspections with wet venting present.

Thank you and Have a productive day ! Milo

And thanks for clearing that up Milo. However, I'm looking for the amendment in the UPC that limits wet vents to remodels and bars them from new construcrion. Since you have the Code Book could you provide me with a explanation? I'm just curious about UPC. Are they beginning to loosen up out there in UPC land? And to find out I'm asking the Master. Regards, Tom

Tom, thank you for your compliment. But I am not "the Master".

Call Los Angeles Building Department, inspector Robert Minassians at 818/756-8901 bet. 07:30- 8:15 AM and 02:30 - 03:15 PM to answer your question regarding wet venting under UPC.

Best Regards
Milo

Maine has a appendix L which is a special section that does alllow a single bathroom group to be wet vented if the lav vent / drain is 2 inches and the trap arms are all correct etc. I should have mentioned that because not many states do. Trust me on that. If that's the case I was still wondering about my original sizing question and any help appreciated.

Thanks

Hi Pbr3232


2" wet vent for entire bathroom. Connect the 1.5" vents from the washing machine and the kitchen sink into a 2" vent and then connect that 2" vent into the 2" wet vent from the bathroom group and connect that into 3" pipe just prior to penetrating the roof full size 3"

In Maine, the 3" vent should be a minimum of 18" and a maximum of 24" out the roof... ;)

Good luck!

MARK

In point of fact Milo. UPC does,indeed, allow wet vents.
908.0 wet venting
UPC code 96 edition
908.1 Wet venting is limited to drainage piping receiving the discharge from the trap arm of one (1) and two (2) fixture unit fixtures that also serves as a vent for not to exceed four (4) fixtures. All wet vented fixtures shall be within the same story; provided, further, that fixtures with a continuous vent discharging into a wet vent shall be within the same story as the wet vented fixtures.

908.2 The piping between any two (2) consecutive inlet levels shall be considered a wet vented section Each wet vented section shall be a minimum waste pipe size of the upper fixture or shall be one (1) pipe size larger than the required minimum pipe size for the sum of the fixture units served by such wet vented section, whichever is larger, but in no case less than two (2) inches.

So there are cases where wet vents are allowed in UPC land. What's next? High loops .on a dishwasher? ( gasp!!). Cheers, Tom




Tom, just wait till you see the 09 addition. No longer limited to VERTICAL wet venting. It will allow horizontal wet venting(actually, our state already allows this) So I think we are making progress,, still no luck on the high loop, but our local inspector allows it, so I'm happy. Reread you post and see what I elliminated,, this is how our code is going to be written,, notice the lack of the word VERTICAL. I will state, I don't yet have a 2009 code book, but this is what I was told by the instructor of my continuing education credits class. Hope he's right(he is definitely correct about it being law in our state).


Ohhhhhhhhhhhh yeahhhhhhhhhhhhh,, upc is back in the game,, lol., or at least giving up and following the other codes,, hmmmm. What the hells it matter, we know what we are doing, what works and doesn't work, but we let a bunch of suits tell us how to plumb,, I think we should get them all out on a real job, and see how they fair., Im betting they would be able to tell us how to do it, but wouldn't be able to do it themselves,. Sorry, long week, have a good one all. Lee.

People use a combination vent to save time and material. Especially now days.

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