On a recent house inspection, I came across a water heater with no discharge pipe connected to the TPR (Temperature/Pressure-Release Valve) and in speaking with the homeowner, I realized people don’t know what a life-saver this little $20 component can be or why a discharge pipe is so important to personal safety. Here is a quick breakdown of what it is, why it’s important, and how you can (sort of) check it out yourself.
WHAT IS IT?
The TPR valve is designed to release water from a water heating device if the pressure or temperature in the tank exceeds safe levels. This is basically what it looks like (this one did not have the discharge pipe connected):
There should be a discharge pipe connected to it that discharges not more than 6-inches above a drain or waste receptor of some kind (like a bucket). In the case of the TPR valve shown here, the discharge is more than 4-feet off the floor and if it discharged could easily scald anyone in the area.
WHAT IF IT FAILS?
Most modern water heaters have redundant safety features but if they fail and the TPR valve is bad, the results can be catastrophic. The water inside can become superheated (above the boiling point) and if the tank ruptures and this superheated water is exposed to the atmosphere, it will expand into steam almost instantly and occupy about 1600 times its original volume. This means a 40-gallon water tank would now be a missile launching out of your basement. Not good.
HOW TO CHECK IT OUT YOURSELF
Please realize that this is only the most basic of visual checks. There are many perimeters to consider from pipe size, valve size, and materials. This is intended to notice obvious problems but if you think there is an issue, I recommend a qualified licensed plumber evaluate your system.
1. Go look at your water tank, is there a TPR valve?
2. Check that there is a discharge pipe connected that terminates 6-inches above the floor, drain, or receptacle of some kind.
3. Check to make sure it is not leaking. Look for signs that it has discharged in the recent past. These are signs that you need to call a licensed plumber.
4. Make sure nobody has capped the valve or the discharge pipe. It seems crazy but I have seen it done. The discharge pipe should not be threaded at the discharge end to prevent this happening.
5. Test your TPR valve every six-twelve months. If you’re not comfortable doing this then please have a professional come out to check out this and more on a preventative maintenance schedule.
***WARNING*** If your water tank has been around for some amount of years and the TPR valve has never been tested, there is a chance that it will not close again. I’ve had it happen to me. When I did it, some sediment from the tank blocked the valve from closing completely and the water could only be stopped by shutting off the water supply to the tank. On this particular unit, the discharge pipe was only a two inches from the wall and I could only fit a small measuring cup under it. Needless to say, that filled up quick and there was no drain nearby. I managed to get it fixed but I have to admit, it was nerve wracking. Moral of the story: Don’t test an old tank unless you have some plumbing skills….call a professional.
Just to be clear, we do not operate TPR valves during inspections and this is a major reason why. (My mishap was on a personal level).
Thanks for reading.