Sump question

[The boring name]

I bought a used tank that was broken down. The tank has 2 holes, presumably for intakes. One is a 90 degree elbow with a hole in the top. The other is just a straight pipe that's a bit taller. I'm gonna return with a pump and some pipe. I'm just a bit confused why there would be 2 intakes. Thanks!

[Fresh2o]

Can you post a pic of this setup?
It’s possible that one holes is the intake and the other the return. The hole in the 90 degree elbow might be a there to prevent water from siphoning from the tank to the sump (hole allows air in to break the siphon).

[The boring name]

Yes I will when I get back home this weekend. See I thought the 90 degree one is the intake and the other maybe a emergency intake? Water wouldn't go it the taller one unless the 90 was blocked. Can I just bypass it by using a valve pvc to plug it?

[Tacit Blues]

It'll really be easier to visualize when there's a picture, but for now, where are the holes drilled? For example, there's the tank I drilled:



So one side is the drain and the other is the return, but they're both in the back. I used to have a tank that was drilled in the bottom and had the overflow coming up via a pipe from there, though.

[The boring name]

This tank has the overflow box, and two holes drilled in behind it in the left back corner. That's why I'm a bit confused on how it would be a return right beside a inlet.

[Tacit Blues]

That’s how the old tank I mentioned was, though as I said came out of the bottom of the tank. Both the drain pipe and the return pipe were right next to each other, but then the return came up and through the overflow box into a loc line, if that makes any sense. And yeah, the return line had a small hole drilled in it to break the siphon.