Second only to the indoor toilet, hot water on-demand inside the house is man's greatest invention when it comes to household creature comforts. There is nothing like a long hot shower (don't tell the drought police) after a day of inspection toil. Especially after emerging from a filthy, wet crawlspace underneath an old house where an assortment of small and medium mammals have made their home over the years. Nasty.
Providing that heavenly hot water is our friend the water heater. Quietly doing its job throughout the years, dispensing a bounty of warmth. What a friend...but potentially the most dangerous appliance in your home.
Tank water heaters are pretty basic in function - cold water fills a storage tank in which the water is heated either by a gas burner or electric elements. When a hot water valve is opened, hot water flows from the tank into the plumbing system, and is replaced by more cold water flowing into the tank. Rinse and repeat.
A water heater that becomes overheated presents a very serious safety situation. Sensors that monitor the temperature of the water control the cycling of the heat source. However, if the temperature sensor malfunctions and allows uncontrolled heating, the water in the tank can reach the superheated stage (past the boiling point). At this point, if the tank were to rupture and the water exposed to the atmosphere, it will instantly expand into steam and occupy approximately 1600 times its original volume.
Now you've got a bomb on your hands. Explosions like this have propelled water heaters like a rocket through walls, ceilings, and roofs, injuring and killing people along the way.
To help prevent this, a safety device known as a Temperature/Pressure Relief (TPR) valve is installed on every tank (and tankless) water heater. Located at the top of the water heater, TPRs are designed to automatically release water in the event that pressure or temperature in the water tank exceeds safe levels.
The valve must be connected to a discharge pipe that runs down the length of the water heater and directs any released hot water to a safe location.
Water heater explosions are a very rare occurrence nowadays, thanks to their inherent safety devices, but like any other appliance there are maintenance duties. Keep an eye on the exit of the discharge pipe. If water is slowly dripping, then the valve is merely leaking and needs to be replaced.
However, if there is a sudden, forceful discharge, then immediately turn-off the cold water supply to the water heater and call a plumber. Test the TPR valve monthly for proper operation by pulling the lever up. Keep your water heater from becoming a bomb.
This blogging is hard work. Time for a hot shower...