All you have to do is turn off your shutoff valves (this would be one of the many reasons to have installed shutoff valves), and your pump and filter will be completely isolated from the pool, allowing you to perform a complete teardown of the equipment if need be. If you did not install shutoff valves, you can try blocking the skimmer hole and return with rags, but you WILL lose some water this way because it will wick through slowly.