Pipe Size for more than 3 toilets

[Rizwan]

One side of our building has 3 bathrooms and the piping from toilets to main pipe is 3". The main pipe is connected to city pipe of 6". We need to add three more toilets on the other side of the building. Can we use the same pipe sizing as the other side? (3" to 4"). Its all one floor. One of the plumber said we need to replace 4" pipe to 6" pipe since we are adding three more toilets.

 

[Terry]

3" takes up to three toilets. When the 4th is added, it's upsized to 4".
Your plumber should know local codes though. Sometimes you have local differences with the inspectors.

 

[Sponsor]

 

[hj]

A 4" pipe can handle a LOT MORE than 6 toilets so either your plumber is mistaken, or he is NOT a plumber.

 

[Terry]

A 4" pipe can handle a LOT MORE than 6 toilets so either your plumber is mistaken, or he is NOT a plumber.

6" would be for a very large condo project perhaps. Very large. I'm trying to remember when I've gone bigger than 4".

Okay, here's a job I did that was larger than 4".
The rain drains for the roof and decks was done in 8" cast.
The parking garage had some 12".

 

[Rizwan]

3" takes up to three toilets. When the 4th is added, it's upsized to 4".
Your plumber should know local codes though. Sometimes you have local differences with the inspectors.

Thank you so much!