I tried out my new Zoeller non-automatic .3 hp sump pump, and the instructions say to drill a 3/16 hole on the discharge pipe about equal to the top of the machine. I did this, and not only does it reduce the discharge pressure, but it makes an irritating spraying sound when the water level drops below that point and the water sprays against the side of the pit. Instructions say that this hole is required to deal with air buildup when used in conjunction with a one- way valve. Does anyone have an opinion on if the hole is really needed?
On another note, I didn't know that the the pump I was replacing was . 5 hp, and it appears that the lower hp of my new pump results in a dramatic drop in pressure. Interestingly, the old pump is actually an automatic unit with a float switch, where they just taped up the switch in an always-on position so that the on/off function is left to the separate switch unit that the pump is plugged into. I didn't discover this until I pulled out the old pump and found the float switch taped to the discharge pipe.