I am worried that I may not have blown all of the water out of my pipes. Picture attached. I drained the filter connected air compressor closed the two valves after the filter which gave me pressure and started with the skimmer workEd my way around the pool plugging the returns and then switched the valve connected to the pump to the main drain waited a couple minutes after bubbles came up turned valve back to skimmer side and turned compressor off. My concern is at some point should I have opened the 2 return valves after the filter and blown those out? If so in what order do I do that. I hope this was clear enough and thank you for any advice you can share...