Wastewater Design Flow for Trailer Court 2

[TimmyH76]

Hello everyone,

We are designing a onsite wastewater system for a trailer court having 31 units. I have found various sources that show the average flow per unit as ~140 gal/day/unit. What kind of safecty factor (peaking factor) would you all use for this situation. Any references you could point me to would be appreciated. Thank you.

 

[Maury]

Ten States Standards includes a graph for the ratio of peak hourly flow to design average flow, based on population. The graph was reprinted from a 1954 book by Fair and Geyer ("Water Supply and Wastewater Disposal").
For the small popoulation you are designing for, the peak flow would be 4.2 times the average flow.

 

[TimmyH76]

Thank you

 

[zabrab]

Maury, a star for you.

I don't have a copy of the actual Ten States Standards, but I have seen references and tabulations to the graph of the ratio of peak hourly flow to design average flow.

In Pa, the design manual is the DEP's version of the Ten States Standards, so I know it is the same or very close to the actual Ten States Standards, but I never obtained Ten States to do an actual check.

I do have a reference that has a graph with Fair and Geyer as the source. It matches the tabulations I've seen for the Ten States graph so I just use it for peaking factors. Thanks to you I now know it is exactly the same as in the Ten States Standards.

FWIW my source indicates the equation of Q peak hourly/Q design average is (18+sqrt(p))/(4+sqrt(p)), where p = population in thousands.