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tonyv

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Just to say hello!
Also , I would like to ask if anyone knows if the following information is sufficient to calculate the flow rate over a weir?
(a) weir width
(b) Height of waterfall
(c) Distance out from base (where the water hits the base)
Thanks
 
Hello and Welcome Tony

I would rather think the return pump size will give the flow rate over the weir.

You can only "overflow" the same amount as what you "return"

Only option that will have an impact you listed is the width.
 
hey there tony, welcome to MASA, great to have you here.

thats a rather tough question first up, but do you want to know the rate of water flowing over a weir and how to calculate it (and if so why??? :))?

i would actually look at asking an hydrolics engineer as they will have calculations of river flows over water weirs, but its a technical quetion which falls well outside my knowledge base:)
 
Actually the answer is really simple.

Look at dams
The width or damwall got nothing to do with the water flow rate. It is more the amount of water entering the system. During low rainfall the HEIGHT of the water over the overflow is low (if any). During heavy rainfall periods, the height of the water over the wall increases and the dam is overfull. That is why a dam can be 105% full.
Doubling the width of the damwall, will halve the height of the overflow.

The same with your tank. It depends on the volume entering the display tank, so it is fully dependant on the return pump size.

Now the real question should be: for a return pump that delivers 2000L/h at my tank top, and you want the height/thickness of the water above the weir to be 5mm, what must the width be?

Somewhere I saw this calculation, but where I do not know.
 
Hello and welcome
 
A VERY WARM WELCOME to MASA, TonyV. Great to have you on-board!

You should get a few more decent answers as well. My opinion is the same as what RiaanP said: what you put in, is what you will get out.
So - your return pump will determine the amount of water flowing down your downpipe/overflow.....
 
Welcome to MASA Tonyv, hope you enjoy your stay with us. Do you have a tank? If yes, would you mind sharing more with us? How long it's been running, how long you're in the hobby etc etc. Better still - some pics???

:wave2:
 
RiaanP said:
Actually the answer is really simple.

Look at dams
The width or damwall got nothing to do with the water flow rate. It is more the amount of water entering the system. During low rainfall the HEIGHT of the water over the overflow is low (if any). During heavy rainfall periods, the height of the water over the wall increases and the dam is overfull. That is why a dam can be 105% full.
Doubling the width of the damwall, will halve the height of the overflow.

The same with your tank. It depends on the volume entering the display tank, so it is fully dependant on the return pump size.

Now the real question should be: for a return pump that delivers 2000L/h at my tank top, and you want the height/thickness of the water above the weir to be 5mm, what must the width be?

Somewhere I saw this calculation, but where I do not know.
Click to expand...
a weir and a spillway are ummmmm different things:) weirs are used in rivers, dam walls hold water and have a spill way, or sluice gates to take the excess water.
 
Yes, agreed Crispin.
Just trying to show the concept. Take a dam wall (where water goes over) or river weir or overflow box. The amount or volume of water is dependant on the flow entering the system.
Less in-flow, less and lower overflow
More in-flow, more and higher overflow.
 
Welcome to MASA!!
 
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