On my RV i need to replace a brass fitting on the plastic tubing near the h2o holding tank, but the old fitting has the 3 rings around it I can't cut the tubing it will cause it to be too short and all the lines seem to be the same so i can't go farther. How can i get the old part out?
you could use a dremel tool with a cutting wheel to cut the rings. if you are careful you will not damage the hose.
You can try WD-40 and hope that the valve is not glued on.
your best bet is to use a dremal with a metal cutting disk you need a steady hand and you will be able to cut at the rings until you can just snap them with your hand then bend it open and pull it off the tubing. if you don't have a dremal you should be able to get one for around 40 bucks and 5 bucks for some metal cutting disks.
soak with WD-40, use red to to get under tubing prying a ice pick, if this does not work try heat to soften tube, match, lighter, torch (be easy u could do damage to tube) try pulling apart after each heating.
if the plastic pipe is grey, you are not going to find replacement (polybutylene pipe) poly pipe fittings are not made anymore. What you can do is get a sharkbite tee and 3 sharkbite couplings and a short piece of pex, copper, or cpvc pipe and make up what you cut out. Poly/pex cutters are sold at home depot or you can cut w/hacksaw
