Skimmer height? why does it matter.

JamesThomas · Jul 30, 2019

I might have thread jacked so Im doing a separate post. Im still not sure why the water level on the outside of the skimmer would matter?? 8"-9.5" etc, when the input is still underwater at only 3"? Im puzzled
does it have to do with water level in chamber just trying to even out disrupting inputs flow?

mtfish · Jul 30, 2019

I am not sure I am answering your question, but I assume you are talking in sump skimmer. The higher the water level in the chamber the skimmer sits, the higher the level of water in the skimmer rises. The trick is when you are tuning the skimmer to skim either on the wet side or dry side, the outside water level plays a role. If the water is too high, the skimmer will overflow and not work correctly. If the water level is too low, the skimmer will not be able to push the skim into the cup, not removing waste as wanted. If the water level is too high, you can set a platform of some sorts under the skimmer to get it to a more optimal working level. Did I get close to the question?

JamesThomas · Jul 30, 2019

You did! and yes this is an in sump skimmer. I believe I have everything tuned properly then. I might try a 1" platform just to experiment. thanks for the reply!

W1ngz · Jul 30, 2019

If the outside water level is too low, in order to raise the inner level the skimmer adjustment restricts the outflow. This creates a back pressure on the pump which reduces overall flow through the skimmer. I really don't know by how much, but restriction = less flow.

That's not necessarily a bad thing, as less flow means more time. The water is in the skimmer body longer meaning there's more chance the impurities get caught in the bubbles before the water leaves the skimmer.

All things being considered, if your skimmer is rated for the volume of the tank you have, and you keep it at the recommended depth, you just have to trust that the manufacturer had the whole thing designed by an engineer with experience in fluid dynamics, and not by an industrial designer who made it look pretty.

JamesThomas · Jul 30, 2019

W1ngz said:
If the outside water level is too low, in order to raise the inner level the skimmer adjustment restricts the outflow. This creates a back pressure on the pump which reduces overall flow through the skimmer. I really don't know by how much, but restriction = less flow.

That's not necessarily a bad thing, as less flow means more time. The water is in the skimmer body longer meaning there's more chance the impurities get caught in the bubbles before the water leaves the skimmer.

All things being considered, if your skimmer is rated for the volume of the tank you have, and you keep it at the recommended depth, you just have to trust that the manufacturer had the whole thing designed by an engineer with experience in fluid dynamics, and not by an industrial designer who made it look pretty.

Lol!! well said and a great point!! I dont need to be an engineer of "all things sump", just know its working correctly and now I can move on stress free. If I didnt overanalyze Id probably realize this whole thing is fun.

DCR · Jul 30, 2019

I think the more significant effect is the air draw through the venturi on the suction of the pump. The deeper the water, the more head pressure the venturi has to overcome and the less air flow. Less air makes the pump push more water and te nds to flood the skimmer. That is why needle wheel skimmers are sometimes very touchy.