Maximum flow a weir can take

[xanthometopon]

Been thinking about trying to run a number of my pieces of equipment off of the weir, e.g. skimmer, UV etc.

What is the maximum sort of flow you can get over a weir before it starts to to be uncontrolable??

Reason I ask is a mate of mine put in a ocenrunner 6500 and the weir could not handle it so had to cut it out, I dont really want to gett inot this situation.

Planning new tank at present

thanks

 

[xanthometopon]

anyone????

 

[BeanAnimal]

I am not sure what you mean by "uncontrollable". When you say his weir could not "handle it", what does that mean?

As flow over a weir increases, so does the crest height of the weir and the friction at the weir surface. That means as flow increases, so does the "roundness" of the wave of water flowing over the weir. At some point surface tension of the water can not keep the shape and turbulance greatly increases, as does the outflow distance. This causes bubbles in the downstream impact zone.

We can make no other assumptions without knowing the length of the weir, the flow volume and the drop on the back side of the weir.

Furthermore, as crest height increases, surface skimming efficiency decreases.

 

[xanthometopon]

I think it was due to the combs at the top of the weir.

They didnt let enough water through

 

[BeanAnimal]

If the overflow has teeth, then increased flow increases the depth of the water at the teeth. At some point you will overflow the teeth. That point is a function of the flow volume vs the area of the teeth.