overflow box


New member
hello my tank is not predrilled and i want to install a refugium, i need to know if an overflow box will keep the water from siphoning out in case of a power failure or should i just install a float valve at the entrance of refugium, thanks



Premium Member
with a overflow and return, when the power is lost water will drain into the sump from the overflow until it's below the intake level. Water can also get pulled back in from the return. To avoid this you can drill a siphon break at the top of the return pipe, or use a check valve. I would also test to make sure the sump can handle the extra water if the power does go out.


Owner of Canada Corals
The overflow boxes sold these days have a chamber built into them that maintains the siphon during power outage.