Do I Need A Vent?

[austinmid]

Here's my situation.

There is an existing horizontal 3 inch drain pipe running underneath my basement. I am running another three inch pipe off the side of it that will run directly to a toilet about 7 feet away. It will have a drop of about two inches per foot. The toilet will not be vented as I hear that toilets operate by siphoning.

There will, however, be a two inch pipe that runs to the p trap under the shower. The total length of pipe will be about two or three feet from the shower drain to the main three inch pipe in the basement (which I imagine is already sufficiently vented).

My question: the unvented shower pipe (though only three feet long) will merge with the unvented (three inch) toilet pipe for about six inches.

Because the toilet operates by siphoning, will it clear the p trap under the shower, thus allowing sewage gas to come up? Do I need to vent the shower prior to the main line? It is only about 2 feet off of the main line, and only the last six inches merges with the toilet drain pipe.

Thanks for your help guys!

 

[johnjh2o]

Both need to be vented.

 

[Matt30]

Every fixture must have a way to vent

 

[austinmid]

Every fixture must have a way to vent

Within how many feet does the start of the vent pipe need to be from the fixture.

 

[austinmid]

I can wet vent into the same main stack higher up, or I can dry vent into the wall. Does it matter? Is one better?

 

[Matt30]

Within how many feet does the start of the vent pipe need to be from the fixture.

6' for 1 1/2" ptrap, 8' for 2" ptrap