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

[Sunee]

Placement of the siphon break is crucial. I have also read somewhere that 2 siphon breaks are a must.
I am testing a new system - also with a small sump and have found I have to curve the loc line up so that the siphon break is just barely below the water line to prevent sump overflow.

[Baldy]

So i guess the amount that flows after the sump pump stops would depend on how much the water level is above the lowest point on the overflow intake. and that would probably depend on how much flow was going through it. anyone with cpr overflows (or others) can tell me how far above the bottom of the grooves of the intake box there water level sits when the pump is running?

[Maverick00]

my cpr doesnt have the grooves your talking about but i try to keep the water level just above the intake so the surface of the water gets skimmed but at the same time doesnt create turbulence and produce air bubbles/pockets. It takes some adjusting to find what works the best. I found I have to keep the prefilter sponge at the back of the cpr as clean as possible (wash it every few days). If i dont the water level in the tank will slowly creep up as it starts to clog with debris and create more resistance for the water flow.

Added: Im using two pvc ball valves, one to limit the return pump, and one to limit the cpr outlet. That will give you full control of the intake and outtake. It was recommended to me in a previous post and has worked great.

[Baldy]

Would a filter sock in the sump be ok to use instead of the prefilter?