Most faucets are rebuildable. The inexpensive plastic ones often have "O rings" or seals like HH mentioned and are available at most hardware and big box stores. The better ones have ceramic discs which are also replaceable. If worse comes to pass, the entire faucet can be replaced with most household lavatory faucets with a 4" spacing. The least expensive household faucets, are usually superior in quality to the standard RV installations.

Gard