Drilled Tank Size

[Sapelo]

Alright, before I begin let me go ahead and say that I knew before I bought the used tank that I should not have done it. Still, it was cheap and I thought I could tackle the problems it presented. Now, a few days into this, I'm having doubts.
The tank is a 265 gallon acrylic. It's been drilled in four places.
1. There are two 1.5 inch holes in the bottom on the right side. I believe there was an overflow box around them at one time as I can still see the lines where it was glued in place.
2. At the top right side, about three inches down, is a 4 inch hole that was clearly used as the overflow drain (it still has the pipe and cover in it)
3. On the left side of the tank, in the same location as the 4 inch drill on the left, is another 4 inch drill.

Originally I was thinking that I could replumb the two 1.5 inch holes from the bottom and reattach an overflow cover/box to use those two as my outflow while leaving the 4 inch as an emergency overflow.
I was also thinking that I could use the 4 inch on the left side as the return flow from the sump.

I'm not all that great at math but I'm beginning to have serious concerns :uhoh2: that the 4 inch holes are just going to be too big for this system.
I would appreciate your thoughts. Thanks!

 

[thegrun]

You should be able to cover them with a piece of acrylic and then drill the size you want. I have no idea why you would need/want a 4" hole.

 

[Sapelo]

Yeah, I was afraid of that. Sigh.

Would you use the two bottom drilled holes or redrill on the back for both intake and return?

 

[thegrun]

Yeah, I was afraid of that. Sigh.

Would you use the two bottom drilled holes or redrill on the back for both intake and return?

It depends on what plumbing configuration works best for your cabinet, either location works fine. I mhave a slight preference for out the bottom (fewer 90's) but I've had a few tanks including my current 50 gallon system with the bulkheads in the back.