Wednesday, October 21, 2009

Replacing a water heater's t/p valve

Hot water on demand at the turn of a handle...what a thing to take for granted! Well, these things only come about by the accrual of many discreet inventions and tweaks (improvements) that the ingenuity of the human mind has pondered and problem-solved.

A temperature/pressure relief valve (t/p valve) is a device on the top or side of a water heater (center of photo below) that exists to safely allow excess pressure to be relieved in the event that, for some reason, temperature or pressure inside the tank of a hot water heater exceeds certain safe limits, like the ability of the fittings to resist being blown out and hot water spewing out in all directions. It has a spring loaded valve that opens if the pressure exceeds, say, 150 pounds per square inch, and allows hot water and pressure to escape via a pipe that is routed to a drain or to some other safe discharge point.

Sometimes the t/p valve itself fails, which in most cases means it relieves itself prematurely. If that happens, you usually will see the discharge or hear it. In our case I heard it, and so knew it was time to replace.

Step 1 is to detach the discharge pipe from the valve so one may unscrew the valve body from the water heater. This is accomplished by means of a pipe or tube cutter, as shown here:

Step 2 is to turn off the water supply to the water heater so that when you remve the t/p valve you don't create a geyser in the water heater room. Find the cold water inlet on the top of the water heater and follow it back to the first valve you come to, often blue in color. (photo below) Water heaters usually are labeled at the inlet and outlet points as to cold or hot. Cold is inlet, hot is outlet. Lifting up on the little lever on top of the t/p valve after you've turned off the supply valve will relieve pressure inside the tank and make it safe to wrench off the old valve.

Below is the old valve removed and you can see the interior that is heavily corroded from mineral deposits in the water. The new valve is in place but not tightened into final position.

With the new valve in place, the discharge pipe is reconnected:

So, it's not the most glamorous aspect of Searock, but these details underlie the creature comforts that we enjoy in even the most mundane of surroundings in this country. Having a plumber invade your sanctuary to do this basic maintenance chore would probably set you back a couple hundred dollars, but this job is easier than changing a flat tire, and you can take a hot shower afterwards. And that is something not to take for granted.

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