Backflow Prevention Input Needed
 

I am in the process of designing my next tank and would like some input on the design.

I want to run as few pumps as possible so I would like to avoid a closed loop system if possible. I would rather use a powerful return pump.

My plan is to use a coast to coast overflow with 8 returns drilled in it.

My question is this...

If I were to use a 8-way manifold on my return line, mount it above the tank/water line and place a small siphon break on the top of it would my tank still drain down to the lowest return line in a power failure?

see pic

If your siphon break works properly, it should stop the siphon before the tank drains down to the level of the return pipes. Can your sump handle the water if they actually do drain down? I wouldn't want to be dependent on a siphon break to save me.

You may need to experiment a bit with how large a hole you'll need to create the siphon break. A large siphon needs a pretty large hole to stop it, otherwise it just behaves like a venturi!

Have you considered that you might not want that much flow through your sump?

The siphon break would be very large, it would actually be another take off from which I would take the line down and into the overflow chamber just above the water line.

I am building a pretty large sump, which I could expand to make room for all the water in my display thus stopping a flood. However I am more concerened about all my livestock sitting in a drained tank everytime the power goes out.

I didn't understand your last question about too much flow through my sump, what did you mean?

If I were you I wouldn't go this route, unless your sump is twice the volume of the display your going to end up with a mirco bubble problem. A CL would be a way better alternative or maybe some stream or vortex pumps. Just a thought.

My main tank will be 120 gallons and the sump will be 185 gallons.
Why would I have micro bubble problems?

You said that you were going to use a powerful pump...so I'm envisioning that you are flowing thousands of gph through the sump- through the OM 8way - through the overflows - back to the sump.

Generally, you don't want to turn the sump volume that fast. If there are any bubbles in the sump (from the returns or skimmer), they could get sucked up in the high flow and get shot into the display tank.

Someone else on the board here was talking about an idea whereby they were going to use 1 single pump to drive the return and a CL (sort of closed). The design was such that the pump would pull from the sump AND from the display tank at the same time. In theory, this seems like it would reduce the flow through the sump...but I couldn't get my head around the backflow potential of that kind of setup.

What kind of compartments are you planning to have in your sump?

It can be done but I think things are simpler having a dedicated CL pump and a dedicated return pump. I know that having one pump is your goal but in the end your going to have a lot less headaches.

Untamed: I couldn't wrap my head around that idea either.

Gotcha, I see what you mean now.

I am going to throttle down the pump for a flow of somewhere around 800-1200 gph, nothing too intense.

The sump plans change by the minute. LOL I may build it even bigger now, deeper. Probably 36" deep x 8' long x 17 wide. I will build a good sized bubble trap. The rest of the sump will be open. I have a 30 gal fuge that will drain into the sump as well. The bubble trap will be on the opposite side of the sump from the return pump, over 7' away.

Ok an 8ft sump is going to work well. I was thinking around 4 or 5 footer. You should be able to double or maybe even triple that number with the size of sump your thinking. Is there any reason why you couldnt make it wider too?

That's what I was thinking. No, the space I am building it in is only 17" wide. No biggy, it should be plenty.