The pressure on the gauge drops to zero. Interestingly, the hose gets heavy when the water pulls through it as it's first connected, but then the pressure drops and the hose no longer has any pressure holding it into the opening at the skimmer. It is still full of water, but the water isn't going anywhere. But what is really odd is that this doesnt happen when the hose isn't connected - the skimmer works just fine, and the pressure is normal.