How much will a 75g drain in a power outage?

[FishKeepingNoob]

I'm building a 20g sump for my 75. The working water level will probably be around half(5.75") of the sump. Unless I need to lower it. The thing is, I have no idea how much water will drain from the tank in the event of a power outage.

Haven't made the overflow box yet. Tank isn't drilled so it will be a hob.

Thanks for any ideas.

 

[jcardona1]

it all depends on your overflow. a normal system will drain 1-2" of water from the tank

 

[Bderick67]

realize that 1 inch of waterline drop in the 75g will mean 3 inches of rise in the 20g. This is if you have standard 75g and 20g high.

 

[wednesday13]

Run a test by setting everything up and cutting the power to the pump. When i run sumps, i add a rubbermaid tote around the sump itself in case of an overflow. It actually came in handy one time when the sump backed up and overflowed.

 

[FishKeepingNoob]

Well, I wanted an idea before I siliconed the dividers in. The sump is a 20 long. Right now, it can accomodate at most 5"(about 10 gallons). I can lower the level in the sump if necessary.