Do Kitchen sinks really need to be vented?

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Birkoff

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I'm not a plumber. I heard a builder say in an exasperated way, "Even though there is no reason for a kitchen sink to be vented, code says it has to be vented, and the code enforcer will agree with you, but it still has to be vented, even though you have to run a pipe up 20' to the roof." It was a comment made as an example, related to the over reaching of government in our day to day lives. Being a curious person I was wondering if the statement was valid, so I thought I would ask the forum. I don't have an ax to grind.
 
I agree a kitchen sink must be vented. it stops the water in the p-trap from being sucked out.
there are approved way of doing his if venting is virtually impossible.
Installing a 2 inch deep seal trap with auto vent is what i would suggest.
 
Over the years in plumbing contractor journals I've seen plumbing engineers demonstrate with math and physics that the size of vents is a bit on the side of caution, like maybe if I recall, a 1" vent would work for many applications...but who's really going to bother testing at this point?
 
The trend in plumbing is “ cheaper “ not “ better “
 
I'd think a kitchen sink MORESO than others needs to be vented. Garbage disposals, and dishwashers would blow s-traps out rather easily.

Maybe the plumber was lamenting on having to atmosphericly vent it instead of using an AAV?

The trend in plumbing is “ cheaper “ not “ better “

I hear ya here. There's rumors of big changes coming to WI plumbing code in the next year, and one of the proposals is changing the minimum on building sewers from 4" to 3". The city and excavators tend to be the ones to put those lines in, and you KNOW they're gonna wanna save the money.

That'll prevent plumbers from ever using (what we call) combination drain and vent in houses (venting floor drains, and the like through stacks), which requires upsizing the whole line. Damned shame, since it saves the plumbers a lotta work.
 
We can do two toilets on a 3” building drain. All sewers must be 4” to the septic or to the city connection.

Commercial building drains must be minimum 4”. Commercial sewers are of course minimum 4”.

Under parking lots must be solid core sch 40 pvc. No foam or thin wall.
 
Thanks all for the responses. I read up a little on vents and can see they are important.
 

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