3 Holes in My Overflow....why?

[Dsoto87]

I recently purchased a 80 gallon tank with a corner overflow. Inside the overflow is 3 1.5" holes. I've only used canister and hobs in the past so I'm pretty new to sumps/overflows/etc...

My question is what is the purpose of 3 holes over 1 or even 2 larger holes. How am I supposed to connect this to a sump? Do I use a 4 way piece of pvc with the holes connected to 3 ends and the last end going to the sump?

 

[SoCalDiscus]

Are the holes in the bottom of the tank inside the overflow? If so, then one would be your drain, and the other two would be your return lines. You would use bulkheads to make the connections for the plumbing.

If the holes are in the side of the overflow box itself, then they are for the returns. The water coming back into the tank from the sump. You can place bulkheads into the holes, and then connect sprayers up to the bulkheads to direct waterflow coming back into the tank.

My setup had both holes in the bottom glass, and holes in the box itself.

 

[Miguel]

Assuming they're in the bottom of the overflow, hole One is for the return of the water to the tank, from the sump.
Second hole is to take the water from the tank into the sump.

The third hole shoud get a higher pipe ( above water level in the overflow ) so that if pipe in second hole gets clogged you have a safeguard against tank overflowing...

 

[SoCalDiscus]

Assuming they're in the bottom of the overflow, hole One is for the return of the water to the tank, from the sump.
Second hole is to take the water from the tank into the sump.

The third hole shoud get a higher pipe ( above water level in the overflow ) so that if pipe in second hole gets clogged you have a safeguard against tank overflowing...

Yes, that would be another way they are setup.

Dsoto87, do you have any pics? That would really help.