Phuntoon;92710 said:I've never wanted a sump because all the horror stories I've read about when a power failure occurs like the main tank water being siphoned down to the sump and overflowing it all over the floor. I'm not extremely knowledgable on sumps but how do you avoid the power failure overflow nightmare when the return pump has no power?
Funny, I just revamped a system at a wholesaler because they were getting floods when they turned off their main return pump!
I think floods are actually easy to avoid, and any horror stories are most likely from people who didn't really understand the whys or hows of sumps in the first place. Its just one of those things I was talking about that once understood, seems obvious.
As sump is a volume of water external from the main tank. Usually it is under the tank. You put all your filtration, heaters, carbon, skimmers and whatnot into the sump so you don't have to look at them in the main tank, and you get a larger water volume in the system which give you a more stable system. For a ceph, you also get the added benefit of having less equipment going into the tank that needs to be octo proofed.
So, you have a line from the tank to the sump (either drilled into the side or back, drilled into the bottom with a stand pipe, drilled into the bottom but in an overflow, or in the form of an external hang on overflow), and a return pump in the sump (or external, depending on choice) that pumps water back up to the tank. Generally these are called a return, as in return to tank, and overflow because the water level needs to reach a certain height for the water to overflow into that line to the sump.
Placement of the return and 'overflow' are important. When the power goes out, water will siphon from the tank into the sump via both the return and the overflow, and will drain as much water as their placement allows. If they have been placed as to allow more water to siphon than the sump will allow - boom, wet floors.
Most often this problem is not from the overflow because the overflow needs water pumping into the tank to, well, overflow. The flooding is almost always from the return being plumbed low in the tank. If the return is 2 inches below the surface of the water in the tank, in a power outage, it will drain the tank to that level. If the return is 1/4 inch below the surface of the water in the tank, in a power outage it will drain the tank to that level. Obviously, the return that is two inches below the water line will drain more water than the return that is 1/4 inch below the water line. In the power outage, the return that drains the tank two inches down also exposes to air anything in the top two inches of the tank - with a ceph not so bad, with corals really bad.
I don't trust things like check valves or anti siphon holes on the return lines. Check valves almost always fail because stuff grows on the surface of anything in saltwater, which will make the check valve not seal and the water will drain. Anti siphon holes get overgrown with muck or coraline algae and need to be tended regularly.
I like to idiot proof my systems so, the returns generally go way up high near the surface of the water. I also use the largest sumps I can and generally run them at a maximum of 1/2 volume so even if some jinky return I set up on the fly slips and is two or three inches below the waterline, the sump can handle it. And, I make sure to power outage test the system to make sure the sump can handle the volume drained into it in an outage.