PDA

View Full Version : Overflow size question


john_blaze
02/15/2010, 05:11 PM
Hello RC, reefer newbie here that needs some help with my DIY.

I just bought a 125 acrylic and plan on using Bean's overflow system. I read through at least half of the 100+ pages, and still have a few questions:

I want to try and put my external overflow on the side of my tank so that the front and back will be visible. I am trying to figure out how much flow I would actually get from a ~15" weir. I tried to use the weir formula to figure it out, but I do not know how high the water will be over the draining edge. I am shooting for ~500gph through my sump (melev's recommendations). From the drain/overflow calc it says that an 8" linear flow with .92" drains will get me 500 gph.

1. How much flow will I get?
2. How big should my overflow box be? A certain depth? Obviously big enough to handle the piping, but is that all I should consider?

I figure that my 15" flat topped weir should allow for ample flow (it will be cut like coyote's if you have seen his build thread), but I want to be sure before I cut into my tank.

Any ideas/suggestions? Will I be ok? I posted this in Bean's overflow thread, but I figured that I would put it here too.

Thanks in advance for any help!!!

john_blaze
02/16/2010, 11:08 AM
Thoughts?..........Anyone?...................Bueller?

das75
02/16/2010, 12:23 PM
Remember the amount of flow is dependent on the return pump, not the length of the weir.

Found the RC calculator, from playing against the calculator on RDO (http://www.reefs.org/library/downloads/) (download is for notched, but use single) and playing with Bazins formula (http://www.aquatext.com/calcs/weir%20flow.htm), gives a height of water over the lip for less than 1/2 inch. Wider for same gph just gives a thinner layer.