Hi everyone, I'm having a problem with my new Goulds j10s. It seems to build pressure well if not using any water but shortly after the pump hits cut-on pressure when using the sprinkler it will drop from 30psi to like 20psi with surges to 30psi. I'm using 1 oscillating lawn sprinkler trying to use 2 will drop the pressure to 0. Dues it sound like a bad pump anyway to trouble shoot this?