depth of flow in pipes 2

[jake07]

hi can anyone help me I have to design a foul drainage network for a housing estate. Dont have a software program so its the old fashioned way! Have most details worked out but the proportional depth of flow is what I have difficulty with. If anyone has an example of a pipe design I would be grateful!!Thanks

 

[jartgo]

What exactly are you trying to do? Generally, proportional depth of flow wouldn't be an issue in design, that is you are either designing at full or half-full (for which the velocity is the same in both cases, hence the equation's simple). If you truly need depth of flow for any other flow, I usually use the nomograph for partial flow in circular pipes (assuming of course you have circular pipes). This tool can be found in several places including the CE reference manual by Lindbergh and the Concrete Pipe design manual by ACPA. There's also someone who posted a spreadsheet recently under the spreadsheets forum that supposedly will get you close. I haven't tried it yet. In summary, there's no simple formula for what you've asked about, but it's generally not necessary for standard designs. Let me know if you need the nomograph, I could probably find one as a pdf.

 

[cvg]

unless your prefer to do it all by hand, there are free software programs out there to help with the design. EPA SWMM is a full featured program that could design your project and can be easily downloaded from the internet.

 

[jake07]

Thanks for that but does that program only deal with stormwater design, as I require a design package for foul waste network

 

[jartgo]

generally waste is considered to have the same hydraulic characteristics as water.

 

[TBCEng07]

Typically here everyone runs a minimum of 6-inch for house laterals or 8-inch sewers for residential developments up to a point (i.e. collector sewers).

You can back calculate the needed sewer size using EPA's rule of 400 gpd / home X peak factor (see 10 states standard). Then use Mannings Equation solve for A using V = 2fps. You probably dont want the sewer to run more than 1/2 full worst case scenario.


10 States Peak Factor
Peak Factor = (18 + SQRT (P))/(4 + SQRT (P))
P = Population in Thousands