The cold water tank in my loft has two overflows side by side, both of which run parallel and straight out the back of the house. One has a 90-degree bend inside the tank meaning the end of the pipe is slightly submerged, while the other is just a regular opening. I understand that the 90-degree bend might be to either stop wind or bugs getting in, or to cause a siphoning effect to make it more obvious when there's a problem with the fill valve. However, those points are largely invalidated by the one right next to it that's just open.
They're approximately the same height, so I can't see that one is intended to be an early warning or anything. A couple of other houses in my road that I can see the back of also have two pipes coming out, so I'm guessing they're set up the same.
Why would there be two and not just a single one? Could it be to do with the potential volume of water? Also why would one have a 90-degree bend and not the other? I've been searching for ages and can't find any information on this so any insight would be much appreciated! Thanks.