Probably not - You would need to flip from the cold drinking water source to your feed tank and after that drain it off (the cylinder stays whole). Following that you could exchange the gate valve ideally with one of these: What should I use to deal with fish if https://andres1mvdk.webbuzzfeed.com/32488720/the-fact-about-how-to-isolate-tanks-that-no-one-is-suggesting