I have a gas hot water heater on a platform in the garage with the pop off valve located on the side. The valve drains with every use of hot water. Is this simply a weak valve that needs replaced or a larger problem? Am I correct in stating that the new valve screws into the tank since I cannot see any threads?
Yes. The big spring in the safety bleed-off valve gets weak after 8 to 10 years, and then the valve starts bleeding and dripping daily. I just had one replaced on my 8 year old heater. They are fairly cheap, and screw into the side of the tank. I had a plumber replace mine while he did other repairs, and it didn't look too complicated. Watch out for scalding water!