That fitting on the line is a 'push-to-connect' fitting. They can be taken apart by pushing one of the lines inward while putting some pressure inward on the small collar where the line goes in. Kind of awkward where the fitting is located, tho. If you have time to go to Lowes/Home Depot, you can see them and how they operate. Its kind of like the chinese finger-grabber---if you just start pulling, won't come apart; have to push inward on one of the lines to relieve the grabber.
It can be done--I just finished replacing my water line and used these connections--much better than copper tubing and flares/compression fittings.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired