Protect your RV water heater from excessive temperatures and water pressure with corrosion-resistant metal T&P valves. All valves are factory set at 150 PSI and are crafted with no gaskets and epoxy-coated probes to prevent corrosion buildup. DH # 421-0423 - 1/2" valve with 4" probe DH # 421-0473 - 3/4" valve with 4" probe