how to calculate drainage for notch..
 

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. :smile:

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?

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

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

Great reference, Thanks Mark