20g Sump Design

[rocket]

Hello All,
I've read through many of the sump threads on this site and I've come up with a sump design that I think will work for me (at least it will fit in my cabinet). From the last thread I posted I decided to abandon the Rubber Maid sump idea and go with a glass tank.
The main question i have is what is the minimum operating depth of a Mag 9.5 before it starts sucking air?
I have a HOB refugium so I don't need a big one in the sump. I have the return/refugium area separated by some "eggcrate" light panel grid.
I have to put my skimmer in the tank so there is enough room to get the collection cup out.
The only other question is how many gallons I need to allow for with siphoning back into the tank when power is off.
Any advice would be great!
Thanks, Nate

 

[esears]

Well, I have a Mag24 as a return pump and it routinely will only have about 4 inches above it and it doesn't suck any air. Down to about 2" and it will start blowing a few microbubbles. Doesn't get really bad until about 1" or so.

 

[rocket]

Good to know, Thanks esears

Well, I have a Mag24 as a return pump and it routinely will only have about 4 inches above it and it doesn't suck any air. Down to about 2" and it will start blowing a few microbubbles. Doesn't get really bad until about 1" or so.

 

[rocket]

Id like to bump that depth from 8.5" to 7.5", that would help with the overflow problem.

 

[esears]

Well, I have a Mag24 as a return pump and it routinely will only have about 4 inches above it and it doesn't suck any air. Down to about 2" and it will start blowing a few microbubbles. Doesn't get really bad until about 1" or so.

 

[rocket]

Anyone else have a Mag 9.5 or larger that operates in 4" of water without a vortex?

 

[class clown]

Well, I have a Mag24 as a return pump and it routinely will only have about 4 inches above it and it doesn't suck any air. Down to about 2" and it will start blowing a few microbubbles. Doesn't get really bad until about 1" or so.

I have a mag 7 and it can operate in about 1-1.5 w/ out sucking the bubbles in, but anything less than that and your flirting with danger. I'd say stick with 2 inch minimum.

 

[burning2nd]

2" is safe, for sure.... you should also think of top off.. when that gets low..


i would lower you glass deviders if you make it so that your sump is runing full all the time.. thats more water that could over flow...

even if my overflow on top falls and my mag pump continues to pump my sump up to the top... ill only over flow about a gallon and a half.

if you make this deep return section thats more that you have to worrie about..

IMO

 

[esears]

Another thing that I did (accidentally of course) is to have the pump angled downwards at perhaps a 30 degree angle. Gives the pump a bit more clearance room, its accomplished by having the pump sit on a few industrial size sponges that were additive free and brand new. Cuts down on vibrations quite a bit since the Mag24 was a LOT louder than I thought it would be.

 

[Meche]

The main question i have is what is the minimum operating depth of a Mag 9.5 before it starts sucking air?

Generally speaking, you do not want to restrict the inlet side of a pump. However, in this case, you can put a elbow on the inlet if you are worried about the pump sucking air. Also, you may want to install a liquid level controller (LLC) to prevent the pump from running dry.

The only other question is how many gallons I need to allow for with siphoning back into the tank when power is off.

This is a simple math problem. Measure the top of your tank (length and width) and measure how far down the siphon break is. Make sure all of your units are in inches and multiply them all together. Here is an example... a 55gal is 48" long and 13" wide, if the siphon break is 2" down then you will need to account for 48*13*2= 1248 cubic inches of water. It sounds like a lot but it is just less than 5.5gal. Also, you will need to account for the volume of water in the hoses. This can be estimated with some common sense.

Now, I had to redraw your picture because it was black&white only? I need colors.

The cubic inches of the 2 "overflow" volumes must match (or be bigger than) the number we just calculated.

 

[rocket]

Thanks for the math Meche, I think I need to experiment with baffle design. I dont think my design will work like I have drawn. but as its drawn I have about 2.9 gallons for overflow. Not enough...

 

[Meche]

I dont think my design will work like I have drawn.

Your right. But it will still work. It may be a bit better if you swap your baffles as I did in my picture. The water level in the skimmer section won't get as high as you drew.