Overflow and Sump Question

[Baldy]

Im sorry if i post this in the wrong section, but it has to do with a sump im trying to design, and i figured it had to do with reef aquariums.

Im trying to stuff a sump into a very small aquarium stand. It is only 25" from the top of the stand to the floor, and with the bottom of the cabinet sitting 4" above the floor, and the door openings it doesnt leave much room. Ive got the size of the biggest tank i could fit in there, and i plan on building it myself out of acrylic (practice for a possible future aquarium =) ). I also plan on using a CPR overflow as my tank isnt drilled for an overflow.

Im wondering, with my 75g aquarium, how much spare room should i leave for if the power goes out? I know if the pump shuts off, the aquarium still flows until the water level is flush with the intake box on the overflow, but im wondering whats a safe volume to account for? 1 gal, 5 gal, 10???

any help would be appreciated

[Maverick00]

it all depends on quite a few factors

-how high you run your water level above the overflow inlet
-how much pvc you are running
-where your siphon stop hole is located on return nozzles

Id recommend running sump as low as you can and simulate a power outage, then you mark out how much higher the level has raised and adjust accordingly

for an example on my 33gal, ill lose only a few gallons back into the sump if the power goes out.

[e46er]

i have 5 gallons or so flow into sump when the return pump shuts off

[Leon71]

I read this somewhere on the net, just not sure where.

Fill your display tank until it starts to spill into the overflow and down into your sump. Fill sump until 1" from the top. Start the pump and wait for everything to level out. Mark this level on the sump with a marker or tape that won't come off easily. This is your absolute top level. Do not fill beyond that line. All is good.

Leon

[Maverick00]

Originally Posted by Leon71

I read this somewhere on the net, just not sure where.

Fill your display tank until it starts to spill into the overflow and down into your sump. Fill sump until 1" from the top. Start the pump and wait for everything to level out. Mark this level on the sump with a marker or tape that won't come off easily. This is your absolute top level. Do not fill beyond that line. All is good.

Leon

i was just thinking about this technique which is a great baseline. However IF you have your intake nozzle/s a few inches below the waterline or more make sure you have a "siphon stop hole" near the surface. When you first fill your display tank up to the overflow all is fine and dandy, until you turn on your return pump which will create a back siphon to your sump if the power should cut out. If your running a small sump with a large display tank combined with lower than waterline returns, a 1" safety net may not be enough. Just something to think about..

[Leon71]

Maverick,

Well spotted. I didn't allow for getting down to the siphon break. Thanks for adding that.

Leon