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Hot Water Heater TPR Valve Discharge Pipe - A critical safety feature
Diagram showing proper TPR Valve Discharge Pipe.
A photo from an inspection of a properly installed TPR Valve Discharge Pipe.
A close up photo of a TPR Valve, without a Discharge Pipe Installed... Dangerous!
By Frank Lundeen - 218 Inspect Home Inspections
Sometimes homeowners or even Handymen overlook critical safety features - like safety features that protect people from being blasted by scalding water... Yes, that's right - there is an appliance in your home right now that often isn't set up properly which could result in severe burning & injury!
I hope I have your attention now!
All tank style water heaters (as well as boiler type furnaces & some on-demand water heaters) have a safety feature that is known as a "TPR Valve" (Temperature Pressure Relief Valve). This is usually on the top or side of the water heater tank, and appears to be a pipe coming out of the water heater tank at a 90 degree angle that another pipe can thread into. There is usually a thin metal lever and a label on it as well. A TPR Valve's job is to release pressure, if pressure gets too high inside of the hot water heater (so it doesn't perforate... or explode if pressure gets too high inside).
The problem is that MANY hot water heaters don't have the appropriate discharge pipe fitted on to the TPR Valve. It's critical that the TPR Valve have a "Discharge Pipe" fitted to it - which brings any water that is discharged from the valve safely down to the floor level (without spraying scalding hot water all over the vicinity). Installers usually choose to use copper tubing & fittings for the TPR Valve Discharge Pipe. There is a list of 18 requirements for TPR Valve discharge pipes, which you can view in this great InterNACHI article.
It's surprising how frequently I inspect a home which has a water heater without a TPR Valve Discharge Pipe fitted to it - I might venture to guess 20% of the homes I inspect! I believe that most of these are DIY installs, where the home owner didn't realize the importance of this safety detail. While it's an affordable & simple fix, a missing TPR Valve discharge pipe shows up on home inspection reports as a Hazardous Defect.
My request of all readers (for their own safety) is to go look at your hot water heater and confirm that your Hot Water Heater TPR Valve does indeed have a Discharge Pipe fitted to it. If not, I recommend consulting with a qualified plumber to address this important safety issue. This will make your home a safer place, and eliminate a potential red flag should you ever decide to sell you house.