Adding a bathroom and a few floor drains in the basement.

[Like_A_Boss]

Soo. . . I recently took on this major reno job. I am adding a full bathroom into a basement. I have already knocked out the trenches and started to install the plumbing. My questions are. . .
#1. If i am tying into the future garage plumbing, am i able to use that 4" pipe as my air vent ? (Picture of incoming garage utilities included)
#2. Do the floor drains i am installing need to be vented ? They will never see heavy water flow. More precautionary measures than anything.
#3. Are cheater vents acceptable to use behind a shower and bathroom sink ?

 

[hj]

Those questions are better answered by your building department and inspector. You MIGHT be able to avoid venting the floor drains if you use a 2" floor drain and a 3" p trap and branch line. This creates a "combination waste and vent system" but it has other requirements also such as a "real vent" before they connect to the rest of the plumbing.