Baffles for a 15 gallon sump... How high?

[20 20]

I know, I know, 'test it to see if it overflows'. But, how can I test it until I build it? So, I'm thinking 8 inch high baffles. The tank is 24 long, 12 wide, 12 high. That leaves 4 inches for overflow, which equates roughly to 4 gallons for overflow when power is cut off. I'll have a simple 1 inch drain from the overflow, and a 3/4 inch return, both approximately 3 to 3 and a half feet in length. This is going to be the sump for a 29 gallon display tank. Is 8 inches a safe height for the baffles in the sump? Any opinions would be greatly appreciated!

[indy]

The baffles don't control whether or not the sump will overflow, they're just used to compartmentalize the sump. The overflow from the display to the sump is what controls the sumps water level.

[pelochas]

i thought the baffles were to control the bubbles from reaching the pump to the tank. it keeps the micro bubbles away

[20 20]

The baffles are used to set up different compartments in the sump, for the drain, the skimmer, fuge, return area, etc. One of the things done with the baffles is to control the bubbles. They don't control an overflow, that's correct. But, when the power cuts off, the water in the drain and return lines, until the siphon breaks, drains into the sump. If there isn't room in the sump for that drainage, the sump will overflow. The higher the baffles, the more water in the sump while it is running, thus there is less room for the 'drainage' when the power cuts off. I'd like the baffles to be as high as possible, while still allowing for adaquate room for the drainage when the power is cut off. I was just wondering if anyone had any basic, rule of thumb' for the baffle heights, before I actually get the glass for the baffles cut.

[indy]

Again, the baffles have nothing to do with either the amount of water in the sump when the tank is running, nor the amount it can take with the power off. Running 20 full height baffles, or no baffles at all, your water will level off the same based on the depth of your overflow. This is of course excluding the small water volume the baffles themselves, or any other object in the sump, displaces.

To tune the water level of your sump is easy, lower your overflow for a higher sump level, raise it for a lower level. Turn off the power to your pump and see where it settles. When you've reached a happy medium, set it and forget it.

[afilter]

A picture is worth a thousand words. Having just built one I know what you mean 20 20. You and indy are both right. Actually build them as tall as you want. Personally I woul leave about 1.5-2" clearance.

Then fill your sump and do a power outage test. When you fill your sump leave the compartment with the pump more than half empty. Measure how much backfill you get and mark it. Do this a couple of times and then fill the pump compartment to leave enough room for backflow.

The first 1,2,3 compartments will fill all the way and then overflow into the pump compartment. If you have you flow rate properly adjusted the water level in the pump compartment should always remain the same minus what evaporates.

Here is a pic:

[acronym:559e0bcf80="For your info"]FYI[/acronym:559e0bcf80], This is a 30g sump/fuge

[acronym:559e0bcf80="Hope this helps (or) Happy to help"]HTH[/acronym:559e0bcf80],

[20 20]

Indy, the height of the baffles DO have something to do with how much water is in the tank when it's running. If the baffles are 4 inches high, that's how much water will be in all compartments except for the return compartment. So, that would leave 8 inches for drainage when the power goes off, or around 9 gallons (8x12x24). If the baffles are 8 inches high, that leaves 4 inches for drainage, or around 4.5 gallons. All that assumes that the water level in the return compartment is lower than the baffle height, of course.

afilter, I like your idea of testing a power outage with different levels in the return compartment, that way I'd be sure to never have the water level to high in that compartment.