how many fixtures on a 3" vent stack?

Ballvalve

Ballvalve

General Engineering Contractor
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northfork, california
1 washer
2 sinks
1 tub
1 toilet

Every plumber joe has a different idea. Can't reach the building inspector, he's always out to coffee.

Seems to me they could all go on the 3" stack....

Its a tough metal roof and I do not want a hundred holes in it.

What do you real plumbers use as a figure?
 
In California, You can plumb a three bath home with one 3" vent.

Most of the time, we would use

2-2" vents, two or three bathroom sets and the laundry thrown in.
1-1-1/2" vent Kitchen

I have only used 3" vents on the West Coast on Condo and Commercial projects.
On homes, I use the smaller vents.

Most of the time, the kitchen is isolated so there isn't much else that can be added.

A 2" line will vent three bathrooms, as long as there are other vents in the system to equal the "area" of one three inch vent.
 
The number of vents through the roof, has LITTLE to do with the number of fixtures, and a LOT to do with where they are placed relative to each other, and whether the vents can be combined into a single penetration. The number of fixtures IS one determinant as to the SIZE of the penetration, however.
 
Most codes are looking for one vent that is 1/2 the diameter of the building drain which in most cases would make that a 2" vent given a 4" drain. However, if you want to know how many fixtures can be served by a 3" stack you will need a copy of your state codebook because they are not all the same. I can tell you with certainty though that you will not exceed that on a residence.
 
quote; Most codes are looking for one vent that is 1/2 the diameter of the building drain which in most cases would make that a 2" vent given a 4" drain

Make that SOME codes. Others require the AREA of the vent to equal the incoming sewer which means FOUR 2" vents for a 4" sewer. Still others require a FULL SIZED pipe from the incoming sewer to the roof. And finally, in some cases after you determine the final size of the vent, it has to be INCREASED in size, (with the minimum size being 4" in many cases), as it passes through the roof to minimize rime frost closure.
 
IPC and UPC which are the two most used codes are both one vent 1/2 the size, but HJ is correct, you need to know what your local code says. BV is in California which I believe is an IPC state for the most part. Obviously frost closure won't be an issue.
 
Looking at the mountains up a bit higher and there is still about 60" of snow to melt....

OK, so 5 fixtures, with only one, the kitchen sink, 18 feet away, can tie into the 3" stack and go out the roof with just one pipe - right?
 
If the kitchen sink is 18' away you are going to have to vent it individually and any other fixtures that are not within trap to vent distance
 
UPC Code, California, Washington, Oregon

Trap arm length.
The distance from the p-trap to the vent.

Table 10-1

1.25" 30"
1.5" 42"
2.0" 60"
3.0" 72"
4.0" 120" unless it's a toilet vent, and then 72"
 
The vent at the sink is very close, but the vent line run to the 3" stack is the 18'

Seems like we should be using automatic vents like a mobile home anyway.
 
Most all "auto" vents only work on negative pressure, not on positive pressure.
They also fail and need replacement.

If you have the walls open, I always prefer a vent through the roof, allowing both positive and negative pressure, that doesn't need repairs and they never overflow.

I will use an AAV in a pinch. But they do have their limitations.
 
quote; OK, so 5 fixtures, with only one, the kitchen sink, 18 feet away, can tie into the 3" stack and go out the roof with just one pipe

Maybe, and maybe NOT. You are NOT telling us HOW the individual vents are getting into the attic so they can be tied together. HOW you do the piping is the important thing, NOT that the "sink is 18' away". That could mean MANY things, some of them legal and others not. It is like you saying, "My car can go 150 mph, is it okay if I drive it", without specifying if you mean on the road or at the track.
 
Well, the bright building inspector did not know the answer - he referred me to my mech. supplier. that guy says 18 +- fixtures on a 3" stack.

Then he says the 18 feet to the stack is ok from the kitchen sink if its 2".

Amazingly, this same inspector allowed the second story toilet to dump into the 3" vent from the downstairs toilet. [not my house, another copy]Never heard of wet vents I guess.

I had to make the "plumber" cut out the run on mine. For my 5 or 6 future fixtures, he was going to put about 4 holes in my metal roof.

I dont know about you guys, but when I see a house where it looks like it snowed vents on the roof, I see stupidity and future leaks.
 
I'm a big fan of vertical.
I like as many of my pipes to go straight up and down as possible.

Popping vents through metal is a bit trickier though. Most of my vents are through comp shingles or cedar shakes.

So.......your inspector never passed his state test? That's kind of sad.
 
quote; Then he says the 18 feet to the stack is ok from the kitchen sink if its 2".

If it does NOT have an individual vent, then 18' is 12' too far. If it DOES have a vent within 6' of the trap, then you can go as far as you have to to reach the sewer connection. That is why we would have to know HOW you are routing the piping, before we can give an answer. Your plumbing inspector is completely useless and must be the brother of the mayor, because if he does NOT know what is permitted, how can he possibly tell if ANY installation is proper?
 
Terry said:
I'm a big fan of vertical.
I like as many of my pipes to go straight up and down as possible.

Popping vents through metal is a bit trickier though. Most of my vents are through comp shingles or cedar shakes.

So.......your inspector never passed his state test? That's kind of sad.
Click to expand...

The inspector is I believe just a failed builder - for a good reason. And the state test I never heard of. Most state test are made for idiots for pass.

I know better than most because I was chosen with 6 others to Re-write on salary and paid vacation a contractors old test that my 5 year wold would have passed.

BUT I would vent a kitchen sink on 40 ' of 2 " pipe and I'll send HJ 10,000$ the day it stops working....
 
quote; BUT I would vent a kitchen sink on 40 ' of 2 " pipe and I'll send HJ 10,000$ the day it stops working....

If you are saying you would put a trap under the sink and then run a 2" line 40', WITHOUT a vent, then it will NOT stop working, but it WILL malfunction, which is a different problem, immediately. And if you did do that, then you might be a "general engineering contractor", (whatever that is), but you are NOT a "mechanical engineer" and should NEVER be allowed to do ANY piping installation.
 
Last edited:
California uses the UPC Plumbing code.
That is not the same as a contractors test.
The State keeps track of time on the job before a test can be taken.
The minimum is 6,000 before the test can be taken.
If you had half that time working with a "real" plumber, then you would be getting closer to understanding what we have been saying.
Right now, it's like discussing plumbing with the hack that stocks the Home Depot plumbing department.
They think that because the stand in front of plumbing parts, that it qualifies them as a plumber.
I sat in front of the teacher in school, but was considered a "student".
The teacher had teaching credentials. Help me out here. Who is a teacher on the site that can tell us what has to be done before you get your own classroom.
 
36 years in the field as a licensed master is pretty helpful

Just for clarity though, the 40' run on a 2" line is not a problem if the pipe is properly pitched but there needs to be a vent on that line within the UPC trap to vent distance. Will the drain function without a vent? Sure it will, but there is a high probablility that with that distance and volume, of the trap being siphoned so either fun a vent up or put a Studor on it if local code allows.
 
Last edited:
hj said:
quote; BUT I would vent a kitchen sink on 40 ' of 2 " pipe and I'll send HJ 10,000$ the day it stops working....

If you are saying you would put a trap under the sink and then run a 2" line 40', WITHOUT a vent, then it will NOT stop working, but it WILL malfunction, which is a different problem, immediately. And if you did do that, then you might be a "general engineering contractor", (whatever that is), but you are NOT a "mechanical engineer" and should NEVER be allowed to do ANY piping installation.
Click to expand...

Dont get your shorts in a wad. Why not wait a bit for the explanation before the insults. Maybe we missed something here. I was talking about the VENT line from the sink, within about 20" of the drain running mostly upwards in order to connect to the single stack out the roof.

The original plumber thought a 3" first floor toilet vent stack could take 2 or three fixtures at most [for venting], and thought it fine to dump a upfloor toilet in that too.

I thought you were saying a 20' 2" pure vent run would malfunction, and I upped it to 40'.

Anyway, I'm not trying to engineer the plumbing, just want it to pass code with a single 3" vent.
 
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