Vent sizing

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cobalt

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see diagram below

My building is a 3 story building.

The main drain is a 4" in the basement.

I have one 2 soil stack and one 3" soil stack that is reduced to 2" above last branch at the third floor. Both stacks are then enlarged to 3" in the attic and exit the roof as 3".

I also have a 3" roof drain that is connected to the 4" main drain.

Questions.

1. Is this installation to code or would there need to be one continuous 3" soil vent/stack vent?

2. Was this type of installation permit in the past?

3. Can the roof drain meet the requirement for one continuous soil vent/stack vent or does the fact that it is flush with the roof surface exclude that possibility?

Thanks for your input?

4E50CF97-ACCC-4FD9-847C-68C79FE7C475.jpeg
 

John Gayewski

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The roof drain cannot be connected to the DWV system. In my area even in an existing structure if the city were to find out they force you to separate the storm drainage from the sanitary.

If you have a 4" drain you need a half of the area of a 4" pipe to vent your plumbing. R²x3.14
 

cobalt

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The roof drain cannot be connected to the DWV system. In my area even in an existing structure if the city were to find out they force you to separate the storm drainage from the sanitary.

If you have a 4" drain you need a half of the area of a 4" pipe to vent your plumbing. R²x3.14
in my jurisdiction roof drains are connected to DWV as there is no separate storm sewage system from housing.

according to formula 2 x 2" vents would work but are there any other specific requirements. if you have time would you be able to address my 3 questions?

thanks
 

John Gayewski

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You have enough venting it's common to upsize as it leaves the structure to inhibit snow outr frost closure.

There could be an interpretation that you actually need two 3" vents or those two two inch sections would need to connect a common 3 inch vent through the roof since each one connects all the way to the main line, but I do not think that would be a common interpretation. Your cross sectional area has been met which would generally be the requirement.
 

John Gayewski

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More of a violation would be the vertical wet venting from floor to floor. That's a no no. If your simplified drawing is accurate then I'd be more worried about that than your vent sizing.
 

cobalt

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thanks for your comments. the drawing is not detailed enough. have updated see below
update.jpg


never though of that.

stack 3: the bathrooms are connected through a vent stack and the number of units are OK for 2". i have 27 fixture units and according to code i am allowed up to 60 units for the length of pipe.

stack 2: there is one kitchen sink on each floor. because the renos of each floor were not done at the same time a vent stack was not installed
the island sink on 1st floor already has "cheater vent" (air admittance valve)
the island sink on 2nd floor i was planning to wet vent. i guess that is a no-no and should use a cheater vent???
the sink on 3 rd floor is dry vented.

what specifically would be the problem in your view?

i want to try and correct any serious flaws as i have the opportunity of doing some demolition.
much appreciated.
 

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John Gayewski

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thanks for your comments. the drawing is not detailed enough. have updated see belowView attachment 82278

never though of that.

stack 3: the bathrooms are connected through a vent stack and the number of units are OK for 2". i have 27 fixture units and according to code i am allowed up to 60 units for the length of pipe.

stack 2: there is one kitchen sink on each floor.
the sink on 1st floor is wet vented
the sink on 2nd floor is wet vented
the sink on 3 rd floor is dry vented.

what specifically would be the problem in your view?

i want to try and correct any serious flaws as i have the opportunity of doing some demolition.
much appreciated.
Specifically the problem is your draining into the vents which isn't kosher. So in your drawing the sink has a vent, but the sink from the floor above is draining into it,same with the drain on the second floor sink. That's not allowed. The stack on the right is more correct.
 

cobalt

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ok i think i get it.

it is virtually impossible that water draining down a 2" pipe from a draining kitchen sink would siphon a lower trap. but anyhow the code is the code.

i guess the proper solution is to run a 1 1/2 ABS parallel as a vent stack which would be so much work. i would have to demolish walls and tiling.

any other solutions? would "cheater vent" (air admittance valve) on 1st and 2nd floor island sinks be a get around?
 

John Gayewski

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ok i think i get it.

it is virtually impossible that water draining down a 2" pipe from a draining kitchen sink would siphon a lower trap. but anyhow the code is the code.

i guess the proper solution is to run a 1 1/2 ABS parallel as a vent stack which would be so much work. i would have to demolish walls and tiling.

any other solutions? would "cheater vent" (air admittance valve) on 1st and 2nd floor island sinks be a get around?
No the trap would siphon itself due to not being vented while another sink runs.
 

Jeff H Young

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Im from UPC Ipc I think allows a 3 inch waste stack to rise and pick up a lav on up to 6 floors from drawings ive seen with out venting and the stack continues straight out roof effectively "wet venting" between floors. As for connecting roof drains and fixture drains probebly places allow it but not in my world. Canada I wouldnt know or any other countrys. maybe there some people from canada
Anybody know what code we are talking about specificaly?
 

cobalt

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Just referenced the National Plumbing Code (Canada). Multi-story wet venting is allowed provided (in the case of 2"):

h) where a wet vent extends through more than one storey, the total discharge
from any one storey above the first storey does not exceed 4 fixture units,


so I should be good with one kitchen sink per floor which is 1 1/2 fixture units.
 

cobalt

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I think I just found the answer to my question 1).

5) At least one soil-or-waste stack or vertical soil-or-waste pipe must extend into a
stack vent or into a vent pipe that is terminated in open air. That soil-or-waste stack or
vertical soil-or-waste pipe must be as far as possible from the building sewer and have a
minimum size of 3 inches up to the outlet on the roof.


This was added in the latest version of the code.
 
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