Herbie Drain

I have a 110G tank that has a corner overflow with two holes drilled in the bottom of the tank. The Tank came with one 1 1/2" an a 1" pvc pipes. One hole will be my main drain an the other will my emergency drain. I have another hole drill in the back of the tank for my return. Does it matter which one of the two different size pvc pipes I use for my main drain ? Should they both be 1" diameter ? I also have the gate valves needed for the setup.

 

What size are the overflow holes? you should use the smaller hole as the drain with a valve on it and larger as the back up.

 

Both bulkhead holes are the same, just the pipes diameter above is different. The responses I seem to be getting are saying to use the larger pipe above the bulkhead fitting as my emergency overflow drain. An put the gate valve on my main overflow drain pipe.

 

Either way should work fine in that case.