Ok, I need to confirm the following:
Instead of venting every fixture, do applicable codes allow the venting of the main drainage pipe for each bathroom?

Regards,

Paul

Hi Paul,
You won't have to vent each fixture. You'll just need one vent for your bathroom group. Read on. Most bathroom groups are roughed in like this.
Toilet connects to sewer main. The toilet wet vents through the lavatory vent. Lavatory connects to toilet drain and runs a vent off the top the stubout tee out the roof or revents back into a dry vent in the attic. The shower connects to the lavatory drain and is wet vented by it. This is a normal rough in and is acceptable both by local and state codes but also The Standard Plumbing Code Book. Good luck , Tom

This is a normal rough in and is acceptable both by local and state codes but also The Standard Plumbing Code Book. Good luck , Tom

Not if you're living in the 9% of the US that has adopted the Uniform Plumbing Code.:D

The UPC disallows wet venting altogether and calls for separate vents for each fixture.

It sure would be a lot easier to answer these questions if the posters would state the location from which they are posting from.

Well, to clear things up.
I am reviewing a design done by a contractor.
What the contractor did was vent the main drain pipe for each bathroom.
I do know that the main reasons for venting are:

1- Preventing siphonage.
This is not a risk in my case, since the entire project - although having a large area (TV Broadcasting Studios) - does not have more than two floors at any given point.

2- Relieving the bad gases from the drainage system, thus preventing the forming of nasty bacteria.

So is this accomplished by venting only the main drain pipe for each bathroom?