Thank you to Real Estate Inspector Michael Thornton for sharing this information that both buyers and sellers need to know about water heaters. If you have not paid much attention to yours, print out this post and go check yours out. You may need to make a few changes.
The most common water heater violations I see with water heaters center around the Temperature, Pressure, Relief (TPR) valve. Water heaters are pressure vessels capable of exploding or causing serious burns. While the pressure vessel itself conforms to ASTM standards, the installation of the TPR valve is installed to the “generally accepted trade practices” of the municipal district. The inherent issues with water heaters lay with the mechanical thermostats, which control the heat source. If the water heater's thermostat malfunctions, the pressurized water in the tank could continue to superheat (beyond 212°F). This will cause two problems:
• First, since water expands when heated, the water pressure in the tank will increase. If the pressure exceeds the maximum pressure threshold (approximately 300 psi) the tank could explode and cause extensive damage to the property or loss of life.
• Second, the release of superheated water (now significantly above 212°F) would immediately return to atmospheric pressure and flash into steam, causing a sudden increase in volume and release of energy. The force of the flash steam would exceed the explosion of one pound of (TNT)!
How TPR Valves Work:
If the water reaches a temperature of 210°F (before superheating occurs) or the water pressure exceeds 150 PSI, the valve will open and release the overheated water. This will allow cold water to enter, lowering the temperature of the water in the tank and consequently the water pressure. The valve will remain open as long as the temperature or pressure exceeds the preset limit. The valve must be located on the tank at the top or on the side near the top, where the water is generally the hottest. TPR valves are not included with the water heater, so be sure that the TPR valve matches the BTU (heat rating) rating of the water heater. A discharge tube must be attached to all TPR valves. A word about discharge tubes:
• The pipe itself must be made of a material that is rated for both high temperature and pressure, which includes most rigid wall copper or iron.
• The size of the pipe must match the opening size of the TPR valve discharge (usually ¾ inch).
• The tube must terminate no more than 6 inches from the floor or be directed to the exterior of the home.
Herein lay the issues that I find with some plumbers or home handymen - laziness or lack of knowledge. Many do not install drain tubes, under size them, or install materials not rated for high temperatures. Water discharging at 150°F can cause serious burns on a person’s torso. PVC pipe is rated for 140°F and will become soft and pliable in the event of a discharge. PVC pipe needs to be replaced with a metallic tubing, CPVC or some other material which is rated for higher temperatures. If you haven’t done so, check to see if your water heater has a drain tube installed and what material is being used. If it is missing, undersized, does not extend to within 6” of the floor, or uses inappropriate materials such as PVC, call your local plumbing contractor.
The Complete Home Inspections, Team
This has been brought to you by Joni Bailey, YOUR Huntsville / Lake Livingston Area real estate professional. Before you buy or sell, call Joni Bailey at (936) 650-9017. I look forward to earning your business and exceeding your expectations.
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