Why is there 3 drains on this sump?

[leighton.bingham]

I have been looking at many sumps, but it seems they all have three drains on them. I know what two of the holes are for. whats the third for?

 

[VintageReefer]

I have been looking at many sumps, but it seems they all have three drains on them. I know what two of the holes are for. whats the third for?

Google Bean Animal overflow

Also it just means the sump is compatible for it. You don’t need to use them

For example my sump has two drains / sock holders. My tank only has one drain. So I only use one on the sump

 

[TX_REEF]

do you have a photo/diagram? Do you mean 3 drains going into the sump from the display? If so, this would be for a "BeanAnimal" style overflow, where there is 1 primary drain at full siphon, one open channel drain, and one emergency drain.

 

[VintageReefer]

Overflow Boxes and Drain Styles - Durso, Herbie, and Bean Animal

Decide which of the three most common types of drains and overflow boxes is right for you and your tank.

www.bulkreefsupply.com