suburban water heater relief valve - dripping

When turning on the water heater, (electric or propane mode) water starts dripping from the relief valve after the water heats up. I fiddled with the relief valve, letting some water spray out of the valve, but it continues to drip fairly constant. I pushed on the pin some and it will quit dripping, but when I let go, it drips nearly a steady stream. Is this usually just a bad valve needing to be replaced?