Quote Originally Posted by JohnT View Post
In a pool plumbing system, decreasing pipe size most certainly will increase pressure. You are restricting flow with the same size pump. Unless your pipe has the capacity to carry much more water than the pump can deliver (not the case with pools), any change in pipe size will result in increased pressure at the pump.
EXACTLY! The water features were supposed to be plumbed with 3/4 inch pipe so the flow rate is much too high causing them to overflow yet there is not enough pressure (or velocity) to allow them to work properly. I have been in contact with the manufacturer to find a remedy for this short of tearing up the deck and repluming although I did have to replace some of the exposed plumbing due to faulty pcv joints and leaks already.