Typical 'check valves' used in RV plumbing whether they have a plastic body or a brass body are nothing more than a plunger/spring/o-ring assembly.
O-ring on end of plunger.....spring held in place with a clip.
Spring holds plunger closed and o-ring seals.
Water pressure pushes plunger OPEN.
O-ring can get shifted out of grove
O-ring can be torn/deteriorated
Plunger can get cockeyed
I hate them because they are plastic junk
Remove them.......install a shut off valve (Sharkbite) and be done with problems.
OR get a true check valve (brass swing check) at Home Depot and replace the junk on with an all metal one
1/2" swing check valve........need short nipples to install
Is it time for your medication or mine?
2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
US NAVY------USS Decatur DDG31