Hi all, I have dealt with RV and Home water heaters for a long time and over the years I have seen numerous attempts to "resolve" a leak (i.e. plugging the hole) that have resulted in some disasterous situations.
TPRVs (temperature pressure relief valves) are a mechanical safety device. Understand that it can be dangerous to mess with a relief valve. You can be scalded or create a very dangerous situation, possibly resulting in death.
Typically they leak for a few reasons:
1. The valve is old and it starts to leak. In our RV's these valves typically sit dormant, unused for great lenghts of time which is bad for the TPRV. A couple of times a year, or at least yearly the handle should be lifted, with the water system pressurized and with COLD water in the tank. This will help clear any built up crud. Do not do this excessively though as it will over time contribute to weaking of the spring mechinism.
2. The water is too hot. water heater relief valves will blow at 210 degrees (typical). Most of the time the relief valve will blow before that temperature because of the extra pressure caused by the water expanding. Many of us (I am one) try to keep the temp of the water heater high and mix cold at the point of use to maximize the time you have warm water for your shower etc. When the temp is set high on the heater you approach the limit of the valve rapidly and minor variances in the system can set it over the edge.
3. The pressure is too high relief valves are set at 150 psi. This seldom seems to be a problem in an RV UNTIL the TPRV weakens. Then the pressure that the TPRV releases reduces. Heating the water increases the pressure in the tank and if the valve is weak, or the water overheated....leak...
4. Thermo expansion - probably the most common cause. Water expands as it is heated, the hotter it is the more it expands. Because of the check valves, backflow preventer etc we all have in our RV's it creates a closed water systems hence the pressure as it builds needs to go somewhere.
I have been lucky with all the rigs I have had. I only had to deal with this once on my equipment. I just replaced the valve which was at that time 5+ years old.
Suburban has a Q&A section on their website which gives alot of information on the entire system for those who are interested.
http://www.rvcomfort.com/suburban/se..._questions.php
Hope this helps, be careful out there. See you when we finally get on the road...126 days and counting.