[shumakerscott]

I will be installing my kitchen sink drain pipe soon. Some people have told me I don't need an outside vent because it is not on a toilet drain. It is stand alone. Half way down the chiminey drain ties in so that is a vent in a way. So, does a sink need a roof vent? Thanks, Dorf dude...

 

[faucetman886]

Vent pipes or waste stacks are needed for 2 reasons. the first is to pipe sewer gases up and out of the system to prevent the associated problems with trapped methane, not normally a problem with just a sink but very necessary with toilets. Secondly a vent allows for the equalization of pressure in the drain lines so that water flows out and down through to your sewer system. Without proper ventilation air bubbles can get trapped and water will not flow easily from a sink. The most common symptom is a sink that gurgles when draining or will not drain rapidly. With this thought in mind all plumbing fixtures should be connected to a vent stack and you should have adequate venting for the entire house. The addition of a new fixture to a vent system can cause problems to existing plumbing if the vent system is overloaded.

 

[TazinCR]

You can install an AAV (Air Admittance Valve) in most areas. Check the code.
http://www.ipscorp.com/studor/maxivent

 

[shumakerscott]

Thanks

After posting I did some research. I should have done that first. Yep, need a vent for sure. Thanks, Dorf dude...