Make Sure it's Safe to Drain Your Pool
Before draining your pool, make sure that your pool will function without water. With a fiberglass pool as opposed to a concrete pool, the water must stay in the pool. If you are sure that it's safe to remove the water from your pool, allow at least an entire day for it to drain.
Rent or purchase a sump pump from a hardware store like Home Depot. Place the pump near the drain of the pool, under water. Connect the sump pump to a hose and connect the hose to your clean-out port. Ask a plumber if you're not sure where your clean-out port is. The recommended allowance for draining a pool is 12 gallons per minute. If you know how many gallons your pool holds, you can calculate how long it will take to drain your pool using this formula.
Turn off the pool pump and drain the filters, heaters, hoses, and all other pool equipment. Place a pool cover over your drained pool until you're ready to refill it. Covering your empty pool will deter trespassers and keep bacteria and dirt out of the pool until you are ready to refill it again.