Venting - What's code?

ChrisJ

This appears to be a difficult thing to answer, because codes vary from area to area.

But, I noticed my dad's house in PA doesn't have the main stack vented full size through the roof. It has a 4" line to the septic and that goes to two 3" in the basement. Those, then go to the roof via a single 2" and a single 1 1/2" from what I recall. It may be two 2" vents, but that's all, no full size stack going out.

That was built in 06 and passed all inspections.

What's the code where you are? Can you have multiple vents that add up to big enough, or does your area also require a full size vent regardless?

PC7060

In Virginia the pipe can be combined to a single 2" line going through the roof. I think the code requirements by state established size of the pipe through roof to mitigate blockage due to frost buildup, snowfall and "just because".

mattmia2

If i recall there is a clause in the model code that requires it be at least 4" or maybe 3" through the roof in areas where it snows. Just because it passed doesn't mean it meets the code.

ChrisJ

mattmia2 said:

If i recall there is a clause in the model code that requires it be at least 4" or maybe 3" through the roof in areas where it snows. Just because it passed doesn't mean it meets the code.

After posting I kept digging, and it appears my dad's area follows IPC code which, best I can tell his house does meet.

And they get plenty of snow. Basically from December - April they have a good foot on the ground.

psb75

Cold weather + prevailing wind conditions can cause frosting inside the pipe at the pipe terminus. It can frost completely esp if the pipe diameter is too small.

Intplm.

Since I started decades ago in the trade, this particular code requirement has changed numerous times.

It was once 18" above and 18" below, with no less then 3" inch pipe through the roof.
Then it was 16" above and below and changed to 12" above and below always no less than a 3" pipe.

The "above" idea is to stay above the snow accumulation on the roof. The "below" is to keep the vent in the conditioned heated space to help prevent frost build up clogging the vent.

If you are in the IPC code area you can find the requirement in that book.
If memory serves, its 12"???

Alan (California Radiant) Forbes

In SF, you need at least one full bore vent stack, usually 4” for residential. Elsewhere (per UPC), you only need to add up all the vents to equal the area of the building drain. Those were tough lessons to learn when you did it wrong, but you always did it right afterwards. 

ChrisJ

Alan (California Radiant) Forbes said:

In SF, you need at least one full bore vent stack, usually 4” for residential. Elsewhere (per UPC), you only need to add up all the vents to equal the area of the building drain. Those were tough lessons to learn when you did it wrong, but you always did it right afterwards. 

They require a 4" in residential in SF?

pedmec

in Massachusetts your required to have one full size stack running undiminished in size from the base of the stack thru the roof. Not more than 24" above the roof line and not less than 18". Size of the stack is determined by fixture units but you can't have more than 3 toilets on a 3" stack. From there, if you have more stacks, the minimum size thru the roof cannot be less than 2".

Mad Dog_2

Bad Practice in any case. Generally all Sanitary codes I have studied, require atleast one pipe, full size from the building house drain, unfinished through the roof. 3 inch minimum.  Anything less than 3 inch could result on Hoare frost sealing off the vent in freezing weather.  Mad Dog 🐕 

ethicalpaul

It seems like the word "could" carries a LOT of weight in the creation of these codes

ChrisJ

My dad just called, he was mistaken the larger one is a 3".

But @Mad Dog_2for clarification are you saying 1 1/2 vents clog all the time with frost?

ChrisJ

ethicalpaul said:

It seems like the word "could" carries a LOT of weight in the creation of these codes

I tend to think a lot of it is "has" rather than could.

Mad Dog_2

No, but when the temperature is right, relative humidity just so, and the occupants are taking hot showers, it CAN happen. I have seen it...pretty cool. A super thin sheet of ice across the opening.  I saw it my friends house in Ozone Park, And. House was built in 1910.  Nothing was draining in the whole house.  Thought is was a stack stoppage.  Went through the booby hathvh to the flat roof to snake 🐍 down.  The 2" C.I. vent terminal has hoar frost.  

Took 10 seconds to absorb what I was seeing. Mind you, I'm a first year Apprentice doing a favor.  I had never even heard the term hoare frost. I smashed it with my Channellocks and felt the Vacuum & rush of the water slogging down the stack...cool.  mad Dog 🐕 

mattmia2

It doesn't happen often but every 5-10 years or so we get just the right air temp and consistency of snow that it sticks to everything, I can see that easily plugging up a smaller vent.

Mustangman

Lots of good knowledge flying around on this one. Most off of it is or was true too...at one time in history. I am an older Master plumber from PA. Venting is probably the greyest area in plumbing. When I started, we had to have one 1 3" minum vent that was the first tee to come off of your building drain. It could pick up fixtures on all the floors but it had to go through the roof, undiminished in size. Then the vent penetration rule was 4" pipe thru the roof. When we went to 1.6 flush toilets, which changed what goes on inside that pipe which use to carry 5 gallons a flush to 1.6. Eventually, venting changed. Currently, and for quite sometime, all fixtures were assigned a fixture unit value. Each pipe size will support so many FUs. A toilet is 4 FU, a sink 1, and a tub, a bidet another toilet. Thats 13FUs so we need 3" pipe as it supports 20 FU. The vent size will seem very small to you. A 2" vent will support up to 24 FU. Vent size is based on fixture units, same as drains. Size vent thru the roof. If its a 2" vent, jump to 3". 3" will go to 4". Small house vents freeze here all the time. Its no joke. I have had people call who's toilets would not flush, strange noises when they flush, Nasty sewer smell, and gurgling drains. All signs blocked vents.
Good luck

realliveplumber

The national standard plumbing code requires the aggregate vent area to equal the required building drain size. (Not the actual size that was installed.)

So if the house requires a 3" sewer leaving the building, your aggregate vent area must be the same in square inches. It does not need to be a 3" pipe, it needs to equal the 3" in square inches, which is two 2" , and one 1-1/2" pipe. Or a 3" pipe of course.

Even if the building drain leaving the building is 4", but the calculations say it needs a 3", that is all you are required to provide in Venting. Most all residential only requires a 3" building drain. (The building drain is the main drain inside of the building, to 3' outside of the building, where it becomes the building sewer. )

The hoar frost portion of the code is not adopted in the NJ edition.

ChrisJ

realliveplumber said:

The national standard plumbing code requires the aggregate vent area to equal the required building drain size. (Not the actual size that was installed.)

So if the house requires a 3" sewer leaving the building, your aggregate vent area must be the same in square inches. It does not need to be a 3" pipe, it needs to equal the 3" in square inches, which is two 2" , and one 1-1/2" pipe. Or a 3" pipe of course.

Even if the building drain leaving the building is 4", but the calculations say it needs a 3", that is all you are required to provide in Venting. Most all residential only requires a 3" building drain. (The building drain is the main drain inside of the building, to 3' outside of the building, where it becomes the building sewer. )

The hoar frost portion of the code is not adopted in the NJ edition.

This is how I interpreted NJ's code, but it's got me confused....

This sounds like you can use multiple vents to achieve the required venting.





But, this sounds like you need a full size regardless? I.E. if you've got a 3" running up to the 2nd floor of a house serving a toilet, it needs to be 3" to the roof regardless of the other code? So a slab ranch the first applies to and you don't need a full size, but a 2 story house does? Did I interpret that correctly?

mattmia2

note that a toilet that holds 5 gallons of water in the tank does not completely empty the tank in a flush so it is more like 3 gallons per flush.

ChrisJ

mattmia2 said:

note that a toilet that holds 5 gallons of water in the tank does not completely empty the tank in a flush so it is more like 3 gallons per flush.

A toilet that holds 5 gallons and dumps 3 would be called a 3 gallon flush not a 5.

There were 5 gallon flush toilets, so I'm told.

Alan (California Radiant) Forbes

So if the house requires a 3" sewer leaving the building ...

Here, the minimum size sewer is 4".

I once installed a drain from a sink in the garage and used 2" cast iron pipe to run twenty feet to the sewer. The inspector made me change it to 4".

realliveplumber

You can use multiple smaller vents to comply.

There are different methods to vent the system. Individual vent, common vent, stack vent.

We size the building drain based on the DFU load.

Larry Weingarten

Hi @Alan (California Radiant) Forbes , It really seems to depend on the AHJ. I built my house with two bathrooms and kitchen, yet my sewer is three inches, as is the main vent stack. There was a lot of talk at the time of oversized drains not working well with low flow fixtures....

Yours, Larry

Mad Dog_2

The less roof penetrative the better. Mad Dog 🐕 

ChrisJ

Mad Dog_2 said:

The less roof penetrative the better. Mad Dog 🐕 

So. Use all Studors?

  

DJD775

Mad Dog_2 said:

The less roof penetrative the better. Mad Dog 🐕 

I agree on minimizing the amount of roof penetrations. Does code allow the vent to come out the side of the house close to the roof line and extend up beyond the roof?

ChrisJ

DJD775 said:

The less roof penetrative the better. Mad Dog 🐕 

I agree on minimizing the amount of roof penetrations. Does code allow the vent to come out the side of the house close to the roof line and extend up beyond the roof?

In NJ yes.

mattmia2

@chrisj according to some quick math my 1930's toilet holds about 5 gallons in the tank and according to the water meter uses about 3 gallons per flush.

This is what the 2015 michigan residential code says about protecting vent terminations from snow and freezing(it seems for some reason we are still using the 2015 code?):

Mad Dog_2

Anything goes in Joisey...."you from Joisey?  I'm from Joisey..."   Mad Dog 

ChrisJ

Mad Dog_2 said:

Anything goes in Joisey...."you from Joisey?  I'm from Joisey..."   Mad Dog 

Is sidewall venting permitted in NYC?

hot_rod

In snow country we always tried to connect all the vents in the attic and have one penetration near the peak. The cross sectional area in vent to match the sewer line, typically 4”

Two 2” does not equal a 4”🤔

ChrisJ

hot_rod said:

In snow country we always tried to connect all the vents in the attic and have one penetration near the peak. The cross sectional area in vent to match the sewer line, typically 4” Two 2” does not equal a 4”🤔

No..
But roughly four 2's does 

Alan (California Radiant) Forbes

12.57 = 12.57

DJD775

ChrisJ said:

DJD775 said:

Mad Dog_2 said:

The less roof penetrative the better. Mad Dog 🐕 

I agree on minimizing the amount of roof penetrations. Does code allow the vent to come out the side of the house close to the roof line and extend up beyond the roof?

In NJ yes.



This would be my preference if building a house and it fit the design. I've had to replace the vent pipe flashing on every house I've owned due to leaks. In the current house I added a 2nd rubber boot over the permanent boot to protect it from UV damage. Still going strong after 10 years.

Panheadsforever

Read the I&O book dor proper venting of appliance

Mad Dog_2

Last I checked absolutely not. NYS neither.  That being said, I'm just about to lay out $1000 bucks for all new $2024 Code books.  Mad Dog 🐕 

ChrisJ

Panheadsforever said:

Read the I&O book dor proper venting of appliance

You do realize this is in the plumbing section and has nothing to do with an appliance, correct?

ChrisJ

Mad Dog_2 said:

Last I checked absolutely not. NYS neither.  That being said, I'm just about to lay out $1000 bucks for all new $2024 Code books.  Mad Dog 🐕 

$1k?  Ouch.


By the way, I did come across this, so not everything goes in Jersey.

realliveplumber

ChrisJ said:

DJD775 said:

Mad Dog_2 said:

The less roof penetrative the better. Mad Dog 🐕 

I agree on minimizing the amount of roof penetrations. Does code allow the vent to come out the side of the house close to the roof line and extend up beyond the roof?

In NJ yes.



There are several requirements that must be met,though

rick in Alaska

When I was in Alaska, you could have multiple penetrations coming out the roof as long as the aggregate area equaled the required building sewer line, usually 3", and they had to be a minimum of 2" because of frost. I always tried to tie all my lines in in the attic so I only had one penetration through the roof, which I made as close to the peak as I could.
Rick

ChrisJ

rick in Alaska said:

When I was in Alaska, you could have multiple penetrations coming out the roof as long as the aggregate area equaled the required building sewer line, usually 3", and they had to be a minimum of 2" because of frost. I always tried to tie all my lines in in the attic so I only had one penetration through the roof, which I made as close to the peak as I could. Rick

What about if you have a 2nd story or higher vertical drop?  That seems to be what most want full size venting on.