I've had my 21000 gallon inground vinyl pool for four years now and I don't know how to drain it. I'm not talking about draining it completely (though I don't know how to do that either) but if I want to lower the water anywhere below the skimmer basket I'm not sure how. I know how to put it on waste and pump out water through the skimmer basket but once it starts sucking in air I've obviously got to stop the pump. I've got a main drain at the bottom of the pool, but my diverter doesn't allow me to close the skimmer basket intake and use only the drain at the bottom. (I can do the opposite, that is close the drain at the bottom and leave only the skimmer intake working) I've tried using one of the vacuum hoses but it usually doesn't seal tight enough to keep the air out as it draws water into the skimmer intake. After just a little time I stop doing that because there's too much air in the system and its not really drawing in water very well. I have tried blocking the skimmer basket intake with a tennis ball which was someone successful but it too began allowing too much air in the system. Can anyone set me straight.