commercial plumbing vent

So I was at my local bank today and noticed the roof had no roof penetrations. Hip style roof just like a house and clay Spanish tiles. I was curious how a building like that would have plumbing vents? I do not do commercial and tried to google this so I walked around the building twice to see if I missed something and not a single vent or stack. So just curious and looking to learn, thanks in advance.

Did the bank have indoor plumbing?

Yeah they have two bathrooms, men’s and women.

Was there a drop panel ceiling near the restrooms to see the plumbing?

I always look above the restroom ceilings if they’re accessible just for this reason, and other reasons too.

Generally a small water heater, exhaust fans, and waste vents are accessible either from a hatch in the sheetrock, or by removing a drop panel.

The company I work for has buildings like that. From what I’ve seen they push the tile up to the stack and then use a lead sheet to cover the gap.

Looked for a picture but apparently I never had a need to take one.

Not needed on a clay roof as the only reason a vent is put above most roofs is the plywood and felt can hold the gas inside the attic.In clay roofs this can’t happen as they have plenty of air movement from the soffit and up. Some older styles rely on the Gable vents also.