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Determining Length of Sewer Throttle Pipe

Determining Length of Sewer Throttle Pipe

Determining Length of Sewer Throttle Pipe

(OP)
How do I determine the length of a sewer throttle pipe?

I need to limit flows to 60 l/sec within a 200DN DI sewer (ks value of 1.5 used)

What is the formula/ way of doing this?

Thanks  

RE: Determining Length of Sewer Throttle Pipe

I am curious what exactly is this "sewer throttle pipe" you are talking about?  If the "ks" is intended to be e.g. roughness "k" (as in Colebrook "formula" etc., that you will find in a good web search), I suspect you might get only 14 or 15 m of head loss per thousand meters or so of that size at least modern, smooth-lined ductile iron (DI?) pipe (and with much lower typical k, at least if intended to be in units of mm) flowing full at that flow rate.   

RE: Determining Length of Sewer Throttle Pipe

Using a smaller bore pipe to restrict pass forward flows and cause the upstream to back up perhaps?

However, neither that or a hydrobrake is ideal.  By restricting the flow you can cause solids to settle out upstream which can cause problems.  Causing blockages. That said, I cannot think of any other ways to do it that dont carry the same risk.  

RE: Determining Length of Sewer Throttle Pipe

Change the slope on a few hundred feet of pipe to get your desired flow rate. Use Manning's find the slope you need. If the velocity goes below 2.5 fps, you will get solid settlement.

Richard A. Cornelius, P.E.
WWW.amlinereast.com

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