For years I have been verifying that water heaters have been equipped with a Temperature Pressure Relief Valve (TPRV). This safety valve is designed to open and release pressurized hot water, in the event that the water temperature and internal pressure inside the tank exceeds preset limits, and prevents the water heater from exploding.

The TPRV is found on the top or the side of the water heater. The TPRV should be properly vented to the exterior or to a safe location. When installed in a residence, attic, or crawlspace, I suggest that it be vented to the exterior in a visible location, pointed downward and terminated close (within 6”) to the ground. When installed in a garage or exterior storage / utility room, I suggest that the TPRV be terminated downward and close to the floor (within 6”) if it cannot be vented to the exterior. In all cases, the TPRV should be vented with ¾” pipe (or same size as the TPRV) and rated for hot water use. I normally recommend that copper or CPVC piping be used. For the code junkies, I am referencing Section 504.6 of the 2006 International Plumbing Code. This section also allows for other means of disposal other than those mentioned above.

In all my years inspecting water heaters, I have found a few with leaking TPRV’s, but I have never found one open or fully releasing water. This all changed on the afternoon of February 2, 2007. I had taken the afternoon off and was involved in the exhilarating task of installing vinyl window shutters on the exterior of my home. The high winds this afternoon made the task just a bit more challenging. These light weight shutters can quickly become air borne on a windy day. I found that by storing the shutters in my attached garage, I could hang one shutter without the fear of a yet to be installed shutter being damaged as it slid across my drive way or was propelled into a neighbor’s house.

As I walked into my garage to retrieve another shutter, I sensed that some thing was wrong. Have you ever entered or been in a room or area and suddenly realized that some thing was just not right, or had suddenly changed? This “sense” may have been triggered by a faint sound, smell, or movement. When this happens to me, the hairs on the back of my neck usually stand up. As I was walking through my garage I heard a faint sound coming from my water heater. I stopped and listened to this unusual noise, just as the hairs on the back of my neck began standing to attention. I quickly realized that the sound of boiling water was coming from my water heater. My first impulse was to shut off the power to the water heater. The circuit breaker for the water heater is in the main electrical panel in my laundry room. As I moved toward the laundry room, which is up the steps next to the water heater and into the house, the TPRV mounted on top of my water heater opened and released boiling hot water!

 Fortunately for me, l had installed a proper drain line on my water heater’s TPRV, and terminated the drain line downward and close to the garage floor. Had I not installed a drain line at the TPRV, the pressurized hot water would have spewed from the TPRV, hit the wall behind the water heater, and sprayed / splattered forth in what ever direction. Being beside (although elevated by the garage steps) the water heater, I would have been within range of the hot water spray. Instead, the hot water hit the concrete floor, quickly spread out over the floor, and filled the immediate area with steam. After shutting off the power and water supply to the water heater, I discovered that the thermostat was defective. After replacing the thermostat, all was well.

While I have always known that TPRV’s are an important safety device, that fact was firmly driven home while mine was preventing me from being scalded. Protect you and your family by verifying that your water heater’s TPRV is properly vented. If you are not comfortable doing this yourself, give me a call for an on-site evaluation or consult with a qualified plumber.