• The tank should be drained and flushed annually to remove any accumulation of lime, iron and other minerals. If lime is found, water softening equipment should be considered. • Anodes should be inspected at least yearly and replaced once they are down to one-third of their original size or show signs of pitting. • If a “rotten egg” odor is present in the hot water, flush the tank with a manufacturer- approved solution and replace the magnesium anodes with new aluminum anodes. 42 National Oilheat Research Alliance Safety considerations Figure 13 Scalding and Legionnaires Disease Water temperatures above 125°F can cause severe burns and death from scalds. Children, the disabled, and elderly are at the highest risk from being scalded. This is because they respond more slowly to exposure. The human threshold for pain is 118°F, and scalding occurs over 125°F. A proper installation will have appropriate valves to protect against scalding hazards. NORA recommends the use of thermostatic anti-scald mixing valves on all hot water destined for domestic use. Having these devices on appliances will also help to ensure that the house has sufficient hot water. Using mixing valves allows us to solve a significant problem that could occur if we merely set the hot water tank to 120 degrees. Low or warm water temperatures allow the bacteria that cause Legionnaires disease, a severe form of pneumonia, to thrive. It is recommended that water temperatures be set at 140°F to kill the bacteria and the mixing valve be adjusted to deliver the correct temperature to the faucets. Temperature & Pressure (T&P) relief valve The discharge drain tube of the T&P valve must be made of material that is rated for a minimum of 150 psi and temperatures of at least 120° F and installed so it terminates plain (not threaded) 6” above the floor drain. Hydrogen gas If a water heater equipped with anodes has been out of service for a period of time, the guidelines contained in UL 174 should be followed” “Hydrogen gas can be produced in a hot water system served by this heater that has not been used for a long period of time (generally 2 weeks or more). Hydrogen gas is extremely flammable. To reduce the risk of injury under these conditions, it is recommended that the hot water faucet be opened for several minutes at the kitchen sink before using any electrical appliance connected to the hot water system. If hydrogen is present, there will probably be an unusual sound, such as air escaping through the pipe as the water begins to flow. There should be no smoking or open flame near the faucet at the time it is open.”
NORA Advanced Hydronics
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