How to drain indoor filter?

Welcome to TFP! :wave: Maybe post some pics of your pool and equipment pad/room so we can see all the plumbing and valves. There should be some shut-off valves before and after the pump to isolate that area from the pool water above. Some water may still spill from the filter and plumbing nearby, but the pool water should not be able to flow past the valves.
 
Hey Jarrod and Welcome !!!!

While we wait for pics, why are you draining the filter ?

Do you have a large shop vac ?
 
Welcome to TFP.

What model filter are we discussing?