On Monday, December 14, 2020 at 8:41:48 PM UTC-5, wrote:
On Mon, 14 Dec 2020 15:46:46 -0800 (PST), Deguza
wrote:
Hello all,

I am planning to add a bathroom to a bedroom. The new one will be about 20 ft or so away from the existing one.

I am in San Jose CA.

Would I need a vent pipe for this new bathroom?

Thanks!

Deguza
Short answer, Yes.
Venting can get pretty complicated but a general rule is if the fall
of the drain pipe is more than the diameter of the pipe you need a
vent. Basically you need a way to break the vacuum created when water
flows through the drain pipe. They do make a studor vent, essentially
a check valve that breaks the vacuum but some building departments
hate them. I don't think you can use them on a toilet at all.
The real answer comes from the building department but I bet they will
want to see a vent typically on the stack from the sink.

+1

If the new bath is on the top story or if it's single story, an additional vent is no big deal.
If not, I think there are other alternatives, like a widget that acts as a one way air admittance
valve. Whether you can use one of those for a whole bathroom though, IDK.