Plumbing question

[kd2777]

Does anyone here know what the correct way to vent a main drain line is?

I bought an older house and have noticed when you send some water down the drain the other sinks, toilets....etc will "bubble". This only happed after I installed the second of two toilets. I was noticing that I didn't have a main vent, which my old house had, so I was thinking this may be my problem.

So my question is, if there are any novice plumbers on here... how would I install one of these. Do I put it in the middle of the main drain line or at the end (this would be my guess). Also how big does it need to be, may main drain is 4" and I have two toilets, 2 vanities, kitchen sink, dishwasher, and washing machine on it.

Thanks for any help.

Kevin

 

[DrPizza]

How's the picture here:
http://home.howstuffworks.com/sewer2.htm

Now, when you have 2 things draining on the same line heading to the stack, then you need additional venting to the vent part of the stack (or simply vented to the outside, creating another pipe sticking out of your roof.