how to calculate drainage for notch..

nanopodreefer · #1 12-04-2006, 07:43 PM

Can anyone tell me how to calculate the max volume of water that will flow through a notch in the top of my tank that is 1.5" ht x 8" lgth, and what is the formula. I looked at the calculators at reef central but they didn't seem to work, thanks.

Pescador · #2 12-04-2006, 08:03 PM

I was playing around with the RC calculator and got this

Gallons per Hour = 800
Recommended minimum drain pipe diameter = 1.17 inches
Recommended minimum linear overflow size = 12 inches

I don't know if that would apply to yours for sure.
Wouldn't it depend more on what size of pipe you have attached to the overflow for the drain?

mark · #3 12-04-2006, 10:36 PM

Bazins formula is what you are looking Q = 0.66 x cB x (2g)0.66 x H1.5
http://www.aquatext.com/calcs/weir%20flow.htm

And from sprdsht I got for flow/height for a slotted weir. Works out for 1.5" over a single 8" wide slot 3820gph

Funky_Fish14 · #4 12-05-2006, 12:03 AM

You must remember to leave some leeway, as that formula is designed for large applications, such as in rivers, etc... In a smaller system, the water will be much more compressed into the small slot while wrapping around the corners of the space, this causes more of a problem with 8" than 50ft. Also, I would definetly shorten B as suggested on the page.

Thanks for the link on that formula, Mark!

Chris

Pescador · #5 12-05-2006, 12:19 AM

Great reference, Thanks Mark