Overflow rates

[shubey]

I'm attempting to determine the flow rate of an overflow box for a new reef
tank which is in the design stage. I have a formula provided to me by a
civil engineer that I think is applicable, but would like to know how others
have gone about determining their overflow rates.

Sharp-crested weir:
Q=C(L-0.2H)H^1.5

where:
C=Weir Coefficient (3.33)
L = Weir Length (ft.) in this case the width of a single overflow slot
H = Headwater depth (ft.) measurement taken from the bottom of the overflow
slot to the tank water surface level

multiply Q by the number of slots in your overflow box for total flow.
(result will be cubic feet/sec)

I am told that this formula takes into account the flow loss for the edges
of the weir (which would be considerable since the slots of a typical reef
overflow box are acting as individual weirs).

For those who already know their overflow rate by actually testing it, it
would be interesting to apply this formula to see if it is in the ballpark.

Thanks.

[Jaime R-S]

lol
Just drain the overflow to a 5 gallon can and measure the time it took...

jrs
"shubey" > wrote in message
...
> I'm attempting to determine the flow rate of an overflow box for a new
> reef tank which is in the design stage. I have a formula provided to me by
> a civil engineer that I think is applicable, but would like to know how
> others have gone about determining their overflow rates.
>
> Sharp-crested weir:
> Q=C(L-0.2H)H^1.5
>
> where:
> C=Weir Coefficient (3.33)
> L = Weir Length (ft.) in this case the width of a single overflow slot
> H = Headwater depth (ft.) measurement taken from the bottom of the
> overflow slot to the tank water surface level
>
> multiply Q by the number of slots in your overflow box for total flow.
> (result will be cubic feet/sec)
>
> I am told that this formula takes into account the flow loss for the edges
> of the weir (which would be considerable since the slots of a typical reef
> overflow box are acting as individual weirs).
>
> For those who already know their overflow rate by actually testing it, it
> would be interesting to apply this formula to see if it is in the
> ballpark.
>
> Thanks.
>

[shubey]

That's exactly what I plan to do once the overflow box is built. However, I
would like to be able to size the overflow correctly before it is installed
in the tank.

"Jaime R-S" > wrote in message
.. .
> lol
> Just drain the overflow to a 5 gallon can and measure the time it took...
>
> jrs
> "shubey" > wrote in message
> ...
>> I'm attempting to determine the flow rate of an overflow box for a new
>> reef tank which is in the design stage. I have a formula provided to me
>> by a civil engineer that I think is applicable, but would like to know
>> how others have gone about determining their overflow rates.
>>
>> Sharp-crested weir:
>> Q=C(L-0.2H)H^1.5
>>
>> where:
>> C=Weir Coefficient (3.33)
>> L = Weir Length (ft.) in this case the width of a single overflow slot
>> H = Headwater depth (ft.) measurement taken from the bottom of the
>> overflow slot to the tank water surface level
>>
>> multiply Q by the number of slots in your overflow box for total flow.
>> (result will be cubic feet/sec)
>>
>> I am told that this formula takes into account the flow loss for the
>> edges of the weir (which would be considerable since the slots of a
>> typical reef overflow box are acting as individual weirs).
>>
>> For those who already know their overflow rate by actually testing it, it
>> would be interesting to apply this formula to see if it is in the
>> ballpark.
>>
>> Thanks.
>>
>
>

[Jaime R-S]

It is trouble... too many variables...
everything from the glass' friction, water temperature, room temperature,
algae buildup, weir thickness and elevation, water rate, direction of flow,
area of tank, and so on will have to be taken into consideration. In some
dams they have a calculation on water flow but its so complicated they can
only get an approximation. I don't think that is what you want...

jrs
"shubey" > wrote in message
...
> That's exactly what I plan to do once the overflow box is built. However,
> I
> would like to be able to size the overflow correctly before it is
> installed
> in the tank.
>
> "Jaime R-S" > wrote in message
> .. .
>> lol
>> Just drain the overflow to a 5 gallon can and measure the time it took...
>>
>> jrs
>> "shubey" > wrote in message
>> ...
>>> I'm attempting to determine the flow rate of an overflow box for a new
>>> reef tank which is in the design stage. I have a formula provided to me
>>> by a civil engineer that I think is applicable, but would like to know
>>> how others have gone about determining their overflow rates.
>>>
>>> Sharp-crested weir:
>>> Q=C(L-0.2H)H^1.5
>>>
>>> where:
>>> C=Weir Coefficient (3.33)
>>> L = Weir Length (ft.) in this case the width of a single overflow slot
>>> H = Headwater depth (ft.) measurement taken from the bottom of the
>>> overflow slot to the tank water surface level
>>>
>>> multiply Q by the number of slots in your overflow box for total flow.
>>> (result will be cubic feet/sec)
>>>
>>> I am told that this formula takes into account the flow loss for the
>>> edges of the weir (which would be considerable since the slots of a
>>> typical reef overflow box are acting as individual weirs).
>>>
>>> For those who already know their overflow rate by actually testing it,
>>> it would be interesting to apply this formula to see if it is in the
>>> ballpark.
>>>
>>> Thanks.
>>>
>>
>>
>
>