Hi - I have a multi family building that I have to put in all new DWV pipe. The configuration is that I have several vertical 4" pipes feeding into a single horizontal pipe. My question is about sizing of the horizontal pipe I'm required to have at different points...

At point A, I have a 3 Kitchens/Bathrooms feeding into the horizontal

At point B, I have (3+1=4) Kitchens/Bathrooms feeding into the horizontal

At point C, I have (3+1+3=7) Kitchens/Bathrooms feeding into the horizontal

At point D, I have (3+1+3+3=10) Kitchens/Bathrooms feeding into the horizontal

At point E, I have (3+1+3+3+4=14) Kitchens/Bathrooms feeding into the horizontal

At point F, I have 14 Kitchens/Bathrooms plus a laundry room with 3 commercial washers feeding into the horizontal - this is just before the city sewer line.

Each Kitchen/Bathroom is fairly standard - 1 bathroom sink, 1 shower, 1 toilet and 1 kitchen sink.

Does anyone know what size horizontal pipe I need at each of these points ? Of if not, could you point me to a book/web page that might help me figure this out ?

Thanks, in advance.

If I'm reading your question right you have have 14 units with a total of 84 bathroom Fixture Units. Add a laundry room with three commercial washers, a floor drain, 14 kitchen sinks with disposals and you get 73 more Fixture Units for a total 0f 157 Fxture Units.
Chapter 13, Table 1305.2 of the Standard Plumbing Code tells me that you can discharge 216 Fixture Units into a 4" line at 1/4" to the foot slope.
If a 4" main gives you concerns you can increase to 5 or 6 nches for a total of 480 and 840 Fixture Units respectively. Good luck, Tom