The only negative effect of having a larger pipe is that if the water has a lot of sediment in it (sand, etc), it can collect at the top of the pump and not be pushed out by the water flow. As the pipe size increases, the flow velocity decreases (assuming the same GPM of water flow), so particles just start to fall back down the pipe and can clog the pump, or cause more wear. Of course, if the water is clean there is no issue at all.
Can i use a larger pipe size than outlet on water pump?
