Hello Chain,
Are you talking about reservoir BP-WTZM250PV2-CLBK?
The long pipe is for water into the reservoir and reducing the bubble.
Is the 3 hole fitting meant to be an intake fitting or an exhaust fitting?
Yes, it depends on you. But the exhaust fitting should be on the top of the reservoir.
Can I have the outlet pipe and 3 hole fitting on the same side of the reservoir?
Yes, you can do it.
https://shop.bitspower.com/index.php?route=product/product&path=65_85_195&product_id=3620