Hayward Sand Filter 240- pressure?

Newbie needs help again. We have 2 skimmers but one is plugged because of leak. We hook the vacuum to the remaining skimmer. The pressure drops to ZERO when vacuuming.....is this normal? Thanks for all your help. Joyce

No it isn't. Do you have a drain? Sounds like the pump is losing prime when you hook the hose up. Are you filling it with water before you hook it up?

Thanks JohnT for your quick response. Yes, we have a main drain in the bottom of the pool. When you say 'fill up the hose' does that mean to completely fill up the hose w/water? If that is what you mean, then I did not do that, only partially fllled w/water. Do you think that is it? Joyce

The hose needs to be full. Hold the end over a return until air quits bubbling out of the vacuum head.

Thank you very much. Will do. Joyce

When the pressure shows zero it means you are not getting water into the pump.
Another possiblity (from not filling hose first) is that your vacuum hose is collapsing and restricting the flow to the pump. In my pool, I have to adjust the 3-way valve so I am drawing half the water through the main drain and half through the skimmer (where vacuum hose attaches) when cleaning the pool. If I let all the water (suction) go through the vaccum cleaner the hose will collapse.

Thank you JohnT & ms. Actually, we think the culprit was the old hose that came with the pool (and the house in Feb). It had been tossed up under the deck..for how long we do not know. It did work for us for 3 or 4 times, but we bought a new one yesterday. The vacuuming went well. We appreciate your quick responses. This forum is so great.....all of you folks helping us newbies. Thank you. Joyce