Source marine or ships self-closing drain valves on m.alibaba.com
Valve Ball 1/2' SST Self Draining Ball Valve
Level glass tap with drain valve, self-closing - Ship Supply Holland
Marine Bronze/Brass Spring Loaded Self-Closing Drain Valve JIS F7398U - China Marine Bronze/Brass Spring Loaded Self-Closing Drain Valve JIS F7398U Supplier - DQ Marine