My water leaks out

Some of these valves are NOT like regular household faucet type valves you might have expected. In fact, many are very lightweight. Instead of having a conventional faucet washer which has a broad and hard rubber surface which gives years of good service in homes - these have something like an o-ring which isn't as strong or wear-resistant. Take your water system valves apart to inspect these o-rings. It's a shame these were used in some RVs because they have to withstand the same pressures as household water systems supply - and a failure at the worng time can leave you stranded with no fresh water.