I'm designing my own nano tank and I want to use an Eheim 1250 as my main recirculation pump. The pump is rated at ~317 gph (I don't know at what head - I'm assuming at 0ft) and has a shut off head of 79". I've estimated that the flow from the pump through the piping, etc will be around 250 gph.
* I need to design an overflow weir sized so that it can take ~ 250 gph
I did a search on the web for flow over a weir and got the following equation:
Q = Cw*L*(2g)^.5 (h)^1.5
Q = volumetric flow rate
L = length of weir
g = gravity ~32.2 ft/sec^2
h = height of water over weir
Cw = constant for type of weir, etc.
I used Cw~0.35 and calculated that I needed:
L = 3" for h=0.75" and Q = 20 in^3/sec (310 gph)
L = 2.5" for h=0.75" and Q = 16 in^3/sec (250 gph)
L = 2" for h = 1" and Q = 20 in^3/sec
L = 1.6" for h=1" and Q = 16 in^3/sec
Does this seem right. This seems pretty conservative - for instance I would need a weir 6" long with a 50% open slotted arrangement to handle 310 gph flow at h = .75"
Do you have any better calculation method or what do you recommend for the open length of a weir to handle my Eheim flow rate?
Please respond and thanks,
Dave
* I need to design an overflow weir sized so that it can take ~ 250 gph
I did a search on the web for flow over a weir and got the following equation:
Q = Cw*L*(2g)^.5 (h)^1.5
Q = volumetric flow rate
L = length of weir
g = gravity ~32.2 ft/sec^2
h = height of water over weir
Cw = constant for type of weir, etc.
I used Cw~0.35 and calculated that I needed:
L = 3" for h=0.75" and Q = 20 in^3/sec (310 gph)
L = 2.5" for h=0.75" and Q = 16 in^3/sec (250 gph)
L = 2" for h = 1" and Q = 20 in^3/sec
L = 1.6" for h=1" and Q = 16 in^3/sec
Does this seem right. This seems pretty conservative - for instance I would need a weir 6" long with a 50% open slotted arrangement to handle 310 gph flow at h = .75"
Do you have any better calculation method or what do you recommend for the open length of a weir to handle my Eheim flow rate?
Please respond and thanks,
Dave
