submerge the hose in the pool first to get all of the air out, then attach to the skimmer.
with a hand vacuum you would be best of vacuuming it to waste in order to get rid of it Al rather then stopping it with the filter and then backwashing.
If your filter is repaired then you can just vacuum the pool.
Vacuum them into the filter.
Most likely the filter. i would check the fingers inside the filter for tears.
To turn on a pool vacuum, first connect the vacuum head to the telescopic pole and attach the hose to the vacuum head. Then, lower the vacuum into the pool and connect the other end of the hose to the skimmer or designated suction port. Finally, turn on the pool pump to start the vacuuming process.
To set up a sand filter for vacuuming the pool, first ensure the filter is turned off. Then, switch the valve on the filter to the "Waste" or "Vacuum" setting, which allows the dirty water to bypass the filter and go directly out of the waste line. Connect the vacuum hose to the skimmer or directly to the vacuum head, then submerge the vacuum head in the pool, ensuring there are no air pockets in the hose. Finally, turn on the pump to start vacuuming the pool.
Check with a pool supply store. There is a small, battery operated vaccum that can be attached to your pool pole. It may be called the pool buster and it costs around $300. The vaccum is battery charged from a standard 120 wall socket and works very well for normal vaccuming.
Add the aluminum sulphate to the pool. Run the filter for two hours. Wait overnight to vacuum the bottom of the pool.
The same as the floor vacuum inside the house but instead of it sucking air it sucks water through the filter. Just run the pool hose from the pool vacuum to the vacuum plate over the top of the leaf basket. then turn on the pump and runi t along the floor of the pool.
There is likely a crack or leak in the hose, filter or pump above water level which is sucking in air and causing the lost prime.
Something blocking it
If you have the regular set up that includes a skimmer, pump and filter then you don't have to waste any water. Get an lid-to-hose adapter, that fits over the skimmer basket at your pool supply store. Fill the hose with water and attach it to the lid. Place the lid inside the skimmer over the skimmer basket, then vacuum to your hearts content. Pool Masters