Critical Analysis and multiple backflow devices
By Tom Lang on Thursday, 12 November 2020
Posted in Irrigation
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I've got a project where the Civil has planned a 4" DCVA to the site, and after this, a 2" DCVA for the irrigation.  The CA only shows a 3psi loss for one back flow device.  Typically, I'd expect to see 6 - 8 psi loss for the 2" DCVA.  So it seems the system accounts for the first backflow from the meter, and disregards the second.  I removed the first one, and the CA showed a 6psi loss through the 2".  Obviously, I need to account for both.  Is this fixable?

 

Thanks!

Tom,

Correct, the system only accounts for one backflow. If you are putting multiple BF on the system, you will need to manually account for that additional pressure loss. Should be as easy as cross checking your residual pressure when running the CA and make sure that additional loss does not put your residual into the negative. We purposely leave that CA as editable mtext so you can modify to your needs past what the system is able to do.

Jake Lott
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4 years ago
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Right.  I'll just add it in...

 

Thanks!

Tom Lang
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4 years ago
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