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Peaking Factor Formula?

Peaking Factor Formula?

Peaking Factor Formula?

I am doing a Sewer Study for a small city in Kern County and in doing so I have been applying the peak factor to obtain my peak flow using this formula:  

PF = 2.65 x Qavg^(-0.1)

However I cannot find anything to reference it to, nor have I found any other formulas that I could use.  Does anyone else use this formula, and if so where did you obtain it?  Thanks in advance.

RE: Peaking Factor Formula?

Seems only fair to ask; where did you get this formula ?

RE: Peaking Factor Formula?

It was obtained from the City of Bakersfield Sewer Design Standards, but it is a copy of a copy of a....well you know, and no one who works for the city knows where the formula was obtained.  The other city I want to use it in is asking if there is a better source or how it was derived.

RE: Peaking Factor Formula?

I ran into that a couple of days ago.
Water and sewer flow factors are somewhere on this website.  Don't remember exactly where, but you'll probably be interested in poking around anyway.  There are lots of design guides, specifications and std methods to be found  here,


BigInchworm-born in the trenches.

RE: Peaking Factor Formula?

Thank you, that site did have some useful information, but I couldn't find anything but a chart that showed peak factors.  

RE: Peaking Factor Formula?

There are many sources for peaking factors. Two I have used are:

Wastewater Systems Engineering by Homer W. Parker and,

ASCE Manual of Practice N0. 37

There are also the Ten State Standards but they may not be applicable in California.

For a small City you may want to use a higher peaking factor than you would for a larger system. See if you can find a City or Cities of similar size and demographics and ask them for flow records for at least the last 2 to 5 years.

Don't forget Infiltration & Inflow; especially if the system is old.

good luck

RE: Peaking Factor Formula?

Lindburg's Civil Eng Reference Manual, cites on page 28-2 the Ten States Eqn mentioned by RWF7437.  While CA is not a contributor to Ten States, I would be shocked if a reviewer refused to accept the validity of anything in it.

Qp/Qavg = [18+(sq rt of Pop in thousands)] / [4+(sq rt of Pop in thousands)].

At Pop=1, factor = 4.5.
At Pop=100M, factor = 1.0.  

That seems very common-sensical to me.

Engineering is the practice of the art of science - Steve

RE: Peaking Factor Formula?

Thank you very much you have all been most helpful.

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