After draining the water out, you should be in "backwash" mode when you turn on your pump. This will make the filter tank fill with water from the bottom up making life easier on the laterals at the bottom and less likely to cause a crack/break on one of the laterals. If you have an air bleeder, keep that open until water starts coming out of it, and then close it. Then you should be good to turn the pump off and switch back over to "Filter" and turn the pump back on.