A water heater safety valve acts as the final line of defense against tank rupture. Over time, internal springs seize up due to mineral buildup, which prevents the valve from opening when it needs to vent steam. You might notice a constant damp patch near the heater or hear a light hissing sound during the heating cycle. Replacing a stuck valve stops small drips from turning into bigger issues. It is a straightforward task, though you will need a bit of thread tape to ensure a snug, leak-free connection.
water heater safety valve
Maximum safety for marine hot water systems.