How Many Vents?

ddawg16

Starting to have fun with the plumbing on my addition....

All of the 'action' in my house is in one main area....in other words, all 3 toilets are actually within 10' of each other...2 downstairs and one upstairs. I also have 2 sinks, one bathtub and one shower to run vents for.

At this point....I'm thinking I will have 2 3" vents sticking out my roof....

I 'plan' to tie the existing bathroom 3" vent into the upstairs toilet vent and run that out the roof....

The other toilet (1st floor) along with sink and shower, I was going to run another 3" vent.

Both of these vents will be within about 12" of each other when they go out the roof.

I recall my inspector making a comment "You can never have enough vents".

But looking at the county's plumbing example....they show that a single 1 1/2" vent is fine for everything.

So...do I do the 2 vents? Or do I tie the 2 3" vents togther in the wall and have just one penetration?

On a related note...I also have 2 bathroom vents in the same area....as in within 12"....is there an issue with some much stuff being so close to each other?

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tylernt

My personal preference is to share vents to reduce roof penetrations. As a general rule, code allows you to share vents BUT the lower floor vents must tie in to the vent stack at least 6 inches above the highest drain in the system (probably the upper floor vanity).

It's also a good idea to increase the vent stack size at the place where multiple vents join, but if you're already at 3" you're probably big enough as it is. I certainly would not use 1.5" to vent multiple fixtures!

Note: I'm not a plumber or inspector, so I make no promises that my advice is compliant with code!

TheEplumber

These are kind of blanket answers

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Alan

The actual rule on the number of vents is that the cross sectional area of the vents must be equal to the cross sectional area of the minimum required drain for the building.

That said, if it's inconvenient to tie them together, more airflow is always better.

Otherwise, minimal roof penetrations = win.

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