Has anyone experienced these symptoms which have got me stumped. When we start vacuuming the pump strainer fills with air and the pump loses prime. I have checked all the inlet piping, and the hose etc. I even replaced the seals and gaskets in the pump. Without the hose on the pump runs fine. No bubbles at all at the strainer or jets. Something is happening when the inlet pressure is drawn down due to the throttling effect of the hose, we then get a slug of air. Where is it coming from? Help!