My concern is I hear alot of talk about peoples tank emptying out on them when they loose power. Should this be a concern? I have never lost power in my complex as of yet but I would rather not risk it. Anything else I need to keep in mind?
People who say these things never setup their overflow properly in the first place. An overflow will stop running when power goes out once the water level drops to a poitn even with the intank portion of the overflow. This is usually less than an inch below the operating water level of the tank when the power is on. What most folks do is undersize their sump or overfill their sump to a point that the water that does back flow from the overflow cant be held by the sump and thus flows out onto the floor. The way to prevent this is to properly size and properly establish your fill level of the sump and not fill the sump beyond that pont.
For a 55 gal
tank I would go for at a minimum a 10gal sump and more realistly a 20 gal
sump. To establish your max operating full level you would fill your sump up to max capacity with the return pump powered off. Then fill your main tank to a level even with the top of the inside overflow box. Start the return pump and start the overflow syphon. The water level in the sump will drop to a point and equlize. That point is your max operating full level. If you power off your pump at this point the water should backflow down to the sump and stop when it gets to the top of the tank and not overfill. Never fill the tank beyond the max operating level when doing topoffs and you will do fine.
Other problems folks have is the overflow not starting back up when power is restored. This is most common with the CPR style overflows. These usually have a bleeder tube that they suggest you put a powerhead on to keep air out of the C overflow channel. The issue is if the powerhead does not start back up upon a power outage. Make sur eyou have a good quality powerhead if you go this route. I personally perfer the U tube overflows as they dont suffer from this air issue as much as long as you dont have water flowing thru the U tube at to slow of a rate.
Always match the return flow of your return pump to be slower than the overflows max flow capacity. For example if your overflow has a max capacity of 600GPH then find a pump that does 500-600GPH at the specific head height you are going to have the pump push the water up.
Fore more info on sumps check out our sumps explained article.