[DutchmenSport]

Before we had the washing machine installed, I winterized the washer lines by connecting a short garden hose to the hook-up (hot and cold) and simply turned the valve at the hook-up. I caught the water and antifreeze in a bucket. Once it started flowing pink I turned off the faucets. When I unwinterized and then sanatized, I did the same thing with those washer hook-up. Never had an issue that way.

Later, we did get a washing machine and dryer. Then I had to learn how to deal with that. But, all good now. It's part of the routine now.

So, you could sanitize those line by hooking up a simple garden hose and let the other end drain outside the camper (if you don't have a short one). Then you won't have to do the valve cut off plumbing right away.