Max/Min Fill line for sump?

[Tetra84]

I'm just getting ready to build my sump and wanted to see if I could get some explanation on how to determine the max/min fill line in the sump. I used the calculator on the homepage to determine what the back flow would be if the power went out, and it said I should have about 4.5 gal free space in the sump. So how does the max and min fill line come into the equation?

[Jeremy Blaze]

Fill the display tank with water til it starts to run into the overlofw and into the sump. Once it stops flowing, fill the sump all the way up.
Now turn on your return pump.
Wait a couple minutes til it is all flowing and the water level in the sump is staying consistant.
The water level in the sump is now your max fill level.

[radone]

Mine is setup to when the tank is running I don't let my min get lower than 1" below the running level. The max is if power goes out or when the pump is off and the sump is full.
What really decides on the max is the amount of water that returns to the system once it's off.
It's always better to have more sump space than needed simply because if it can happen it will.

My ATO controls the water level in the sump which is no more than about a 2" increase or decrease either way

HTH

[Curl58]

The min line is pretty simple, what is the lowest amount of water you can have in the sump and not have the return pump pushing air. I keep my min line at least a couple inches above my return pump. The max line is critical as it will determine if your sump will overflow in the event power is lost. You need to turn off your return pump and let all the water drain into the sump. Then fill up the sump to the max level you want with the return pump off. I keep mine about two inches from the top. Then you turn the return pump back on and once the sump water has leveled out, that is your max. That may you know if the return pump ever stops it will not overflow.

[Jeremy Blaze]

The min line is pretty simple, what is the lowest amount of water you can have in the sump and not have the return pump pushing air. I keep my min line at least a couple inches above my return pump. The max line is critical as it will determine if your sump will overflow in the event power is lost. You need to turn off your return pump and let all the water drain into the sump. Then fill up the sump to the max level you want with the return pump off. I keep mine about two inches from the top. Then you turn the return pump back on and once the sump water has leveled out, that is your max. That may you know if the return pump ever stops it will not overflow.

Thats what I explained above.

[radone]

Tetra
One other thing to mention that if you have an nozzles or your return lines submerged this will also affect the "Max" level. Meaning the return lines "Need" to draw air to break the siphon so any line that is below the running water level of your tank has the ability to siphon water back to the sump.

Hope this makes sense

[Tetra84]

So when it comes to adjusting the water level in the return section for the minimum level, is that a factor of how much you have the return pump's ball valve closed, or how high the last baffle is? Also, do you want to do this max/min test with freshwater or saltwater?

[Tetra84]

Tetra
One other thing to mention that if you have an nozzles or your return lines submerged this will also affect the "Max" level. Meaning the return lines "Need" to draw air to break the siphon so any line that is below the running water level of your tank has the ability to siphon water back to the sump.

Hope this makes sense

So for this case, would you just make the return nozzle as close to the surface of the water you can?

[radone]

Yes keeping your return lines close to the top is good but there are ways to create a siphon break besides this.
If you follow Jeremy's method you'll be fine.
If it was the first time I would use freashwater just to be on the safe side but you'll need to drain it.

BTW what size aquarium and sump?
and yes your last baffle will determine the lowest level for your sump, provided you use the over under over method that would be three baffles. A single baffle yes that would be the lowest without starving the return pump.
A ball valve on the return will restrict the gph back to the display, I run a dart and mine is full throttle. I also have a 75g as sump so it is a matter of your situations.
FYI generally if you restrict the output of a pump it will lower the electrical usage also. But other stuff may require the flow

[Tetra84]

My display tank is 57 gallons, and my sump is 15. I figure I don't need to have anything in the display tank for the freshwater test, but the sump should have everything in it (rocks/sand/equipment) that will displace the water for this test I assume? My idea for my sump was the first section with the protein skimmer, then the over/under/over baffle followed by the fuge section, and lastly the return pump. I was planning on making the last baffle just above the return pump, and wall the rest of the area off with eggcrate.. will this work? Also what's the best way to break the siphon on the return pump?

[sleepydoc]

An easy way to estimate the amount of water rise in your sump without actually filling it with water is by comparing the ratio of the tank surface areas. If the DT is 2' x 3' = 6 sq ft and the sump is 1' x 2' = 2 sq ft, the ratio is 6/2=3, so for every inch of water that drains from your DT, you could expect the sump to rise 3". There will be a bit extra due to the volume of the pipes/tubing, but usually not too much.