The Camco 22223 valves and similar valves from other companies leak, are hard to turn and get brittle and break as you found out. I've replaced mine (which have been used as low point drains) three times in five years. I've been searching for a metal replacement for years and finally found the necessary part to make one on E-Bay. It is a machined aluminum part that has a stepped, barbed nipple and flange into which you screw an automotive, air compressor, or similar drain valve. The round flange is the same diameter, has the same size mounting holes with the same spacing as the plastic drain valve that it replaces. The listing is called: "RV Freshwater Drain Valve Flange" and is found at RV Fresh Water Drain Valve Flange 3 8" or 1 2" Won'T Fail Ever Again | eBay
. It is expensive but is beautifully made and anodized. I bought three and they work perfectly and should last forever.