Sanitary line size 2

[antony09]

I need to design a sanitary line, I am using the building drains and sewers to select the maximum number of drainage fixture units connected to any portion of the building on the building sewer. In this moment i am design a office building with 2400 drainage fixture units to 1/16 inch slope per foot, so i need to use 10" diameter of pipe. But other designer said that i need to apply a diversity factor of 0.6 according the ASPE to the hunter curve. After apply this factor the quantity decrease to 1440 dfu. Therefor the pipe size will be 8" Any body could help me to resolve this doubt.

 

[bimr]

The fixure unit values represent the probable flow that fixture will discharge into a drainage system, compared to other fixtures.

The fixture unit values have been revised over the years since the development of the Hunter method using long term data and modern statistical methods and analyses.

If you are using modern fixture unit values, you do not use the diversity factor

 

[antony09]

Thank you bimr, I am using the Figure 7.2 "Drainage Fixture Units for Fixtures and Groups and Figure 7.6 Building Drains and Sewers. Both Figures from Plumbing Codes Handbook 2000.
By the way the sanitary civil engineer that design the utility sewer line, What kind of concept do they use to design this line. Because i think that they use other tables to size these lines. the values show in the Plumbing Codes indicate higher values.
Could you clarify it??

 

[Maury]

Civil engineers use a different system for sizing lines than is found in the plumbing code. We use something called a Population Equivalent (abbreviated PE). One PE is 100 gallons/capita/day. Single family homes typically have a PE of 3.5, condos and apartments have smaller assumed values based on the number of bedrooms. Basically, PE is the actual population. Since buildings such as offices, schools, restaurants, businesses, etc., don't have a resident population, studies have been done to develop PE numbers for design use. Consult your City, Sanitary District, or state EPA for recommended values.

Where I'm at, here are some of numbers we usefor daily flow:

Office & Business PE = 0.15/worker/shift
Factories PE = 0.35/person/shift (not incl indust. wast)
Hospitals PE = 2.5/bed
School PE = 0.15/person (w/o gyms, cafetertia)
School PE =0.25/prtdon (w/ gyms and cafeterias)

 

[bimr]

There are two accepted methods to estimate the flows.

Maury described the first method, the per capita flow method.

If your flows deviate from the per capita estimate, you can use the second method as an alternative to the per capita flow method. The second method is to prepare a detailed study and estimate using fixture flow rates. You will also have to prepare a brief decription of the procedures used in your evaluation.

 

[mytu]

I have been used the Hunter methodology for several years and I know that the Hunter curve for discharges is higher than that used for water supply. Hunter is generally accepted for internal plumbing to the connection at the general drainage systems, not using any reduction factor its recommended due to safety factor. For exterior or utilities drainages you must use the PE methodology in witch you can't use the fixture numbers.