overflow box, possible way to prevent it from completely ruining my system?

[celacanthr]

Well, I am almost a complete DIY dufuss, but I hope I can learn more.
Well, I have been trying to settup a sump/refugium FOREVER! But alas my tank is not drilled, and has a DSB, so empteing it to take it to get drilled IS NOT an option.
So I read around, and realized that an overflow box is my only option. I also realized through my reading that overflow boxes carry a risk that the siphon might fail, causing the water in the refugium to continue to pump back into the tank, thus overflowing it. Couldn't this overflow be prevented bye just making baffles in the refugium? also, since I may be using on odd shaped container for my sump, it may be difficult to make baffles, so I may need another option. Could I make the outflow from the refugium be pumped back bye a pump that is in the main tank, so that if the water runs low,the pump will jsut burn out instead of flooding my room?
thanx in advance!

 

[reefraff]

If you have the right size tank and sump you can make a flood proof system. If you adjust the overflow box so the water level in the tank is just at the lower lip of the top molding you can pump quite a bit of water in without overflowing the tank. Depending on the tank size you may need to make a baffle in the sump/fuge but you will need that anyway.
The way I did mine was to set the height of the overflow box so the water level in the tank was at the bottom of the top molding. I then added enough water to the tank for the overflow to fill the sump to about an inch of the top. I knew if I lost power or had a pump failure there would be no flood. In my case I was lucky and when I started the pump and stopped the siphone there wasn't enough water in the sump to overflow the tank so I didn't need to make a baffle. I had a pretty small sump for a 125.

 

[darknes]

One thing I've heard, and I'm going to try when I finish my DIY overflow, is to drill a hole in the top of the overflow tube. Then, attach an airline from there to a powerhead in the tank (most powerheads have an airtube attachment). Supposedly, this will always suck out any air that builds in the overflow tube. So, if for some reason the siphon breaks, it should be able to start a new siphon before the tank overflows.

 

[juiced_rl]

I have recently purchased a Pro Clear sump for my 55 gal. with an overflow. I have also researched this alot and everyone seems to recomend in getting the U-Tube style over flow which I did. I have cut power to the return pump about 100 times in the last few weeks just for testing purposes and have had no problem with any air getting into the tube. I was worried about the overflow issue but from what I have seen is the only thing you would havto worry about is back siphone from your return and that is easily fixed with drilling a hole just above or below the water line in your return tube.
I say don't worry as long as you get the U-Tube style overflow.

 

[acrylic51]

I don't think their is anything fail proof in this hobby, but you can come close.....It's not that common to have a HOB overflow loose syphon just out of the blue.....Usually it gets clogged, by a snail or algae or something other....These things can be prevented from happening, but my 300 gallon in my family room has been running for 5 years and even through power outages and such it has never just lost syphon. I can drain the tank down 2" below in inner overflow box and then bring the water level back up and fire the pumps again and all is fine......the water level inside the inside and outside back portion should keep the U tubes covered to keep the syphon.....
A key is to drill yourself a syphon break hole as mentioned above and also not to ever overfill your sump for whatever reason...With that being said you should be relatively safe.....