Skimmer question?

Im thinking of using a 20g 30"Long x 12.5"Tall x 12"Deep as my sump for my 90g, my question is..how many inches of water do i need in the sump for the skimmer to properly function?

Most likely going with...Reef Octopus NWB150 6” Pinwheel
In Sump Protein Skimmer...Dimensions: 12" x 8.5" x 22.13"

Will this set up work?

Thanks in advance for answering my noob question.

 

You'll need to look at what the manufacturer says.

 

Water level in sump should be 6”-10” as long as​

it is not covering the water outlet pipe.

Heres the manual.

http://coralvue.com/wp-content/uploads/downloads/2010/05/NW150B-Instructions.pdf

 

Ill tell you I have used two different RO skimmers and they recommended 6.5 inches of water depth but they both did fine in 9 inches.

 

i have the exact one your looking at, works awesome in 9" of water for me.

 

12.5" is pretty shallow for a sump. You can find a skimmer that works, but you bigger concern is having the reserve volume in the sump to handle the drain back when you kill the return pump. I'm not saying the 20 gal will not work... but you need to do the math and figure out how much water you have draining back. And you will need to do everything you can to limit that amout. A 20 gal cuts it close... and no, check valves are not the solution. Everything mechanical fails at some point. You can use them, but do not rely on them to prevent a flood.