Power Off DT water height

[Baldy]

Hello all,

Im crunching the numbers on a sump for my 75g. due to a short stand, i dont have much height to work with, so im trying to utilize all the space i have available.

My design thus far has room for 19g when its running, and 3" of space between the water level and the top edge of the acrylic. ive calculated that to stay 1" away from the top edge, i would have to have 4.29g flow from the display tank into the sump after the return pump is shut off, and i could have 6.43g flow before it starts overflowing.

this translates into 1-1/4" safe water height drop in the display tank, and my sump would overflow if it dropped more than 1-7/8".

I plan on running a 1200gph lifereef overflow (not willing to drill the tank at this time), and a mag12 return pump. so my question is this, how much can i expect the water to drop when the power to the return pump is shut off? has anyone ever measured their own DT?

[The Grizz]

Really it all depends on how much water is above the teeth on your OF? What type of OF you have, water in the OF lines & if your return will siphon any extra water out of the tank. I tried to figure it out on one of my tanks mathematically but ended up going with the fill tank, kill the power & see what happens method.

[Baldy]

so when you filled the tank and killed the power, how much did it drop?

i dont have everything here to be able to try it out, and i want to make sure that the water level i chose will leave enough room to be safe before i get all the acrylic cut

[The Grizz]

All my OF acrylic teeth are about 1 1/2" long so my water level drops about an inch but my tank is also 165 gals with a 65 gal sump so I would say close to 20 gals into my sump when the power goes off.

[Baldy]

Lol, yeah you will be flowing over wire a bit more than me. Like I said on my first post, I'm going to be using the lifereef overflow, and I don't think (read: I hope) the teeth aren't that long

[mark]

backflow; it's going to be the volume of your overflow chambers (or less if you have a standpipe in them), volume of your display until you reach the siphon break of your return outlet plus the volume in your lines.

Best to fill your tank until it overflows into the sump, then fill you sump to your max height your comfortable with. Turn on you pump and mark the level that your sump settles down to as something like "Max fill, pump on" and adjust you ATO to the level as well. If you never top up above this mark with the display running, you won't flood.

As said every display will be different amounts because each each tank will be a little different. My case I'll backflow ~26g but is easliy handled since I run my 75g sump little over 1/2 full.

[Baldy]

Originally Posted by TheNewGuy

i dont have everything here to be able to try it out, and i want to make sure that the water level i chose will leave enough room to be safe before i get all the acrylic cut

^^^

[mark]

and if you set your "max fill" level as described no matter how you cut your material and build you tank, you'll have enough room. Your return pump might be sucking air but you won't flood .