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== Criticism ==These devices are not without their pitfalls. One major concern is the increase in overall expense to the homeowner. There are many homes where the hot water heater temperature is not set high enough to cause dangerous scalding. It is not necessary to have a hot water heater with a setting above 120 degrees, and it is actually quite sensible to have it set at 110 degrees. This saves the homeowner money. The most common regulatory standard for the maximum temperature of water delivered by residential water heaters to the tap is 120 degrees Fahrenheit/48 degrees Celsius. At this temperature, the skin of adults requires an average of five minutes of exposure for a full thickness burn to occur.If a homeowner has a commonsense temperature setting on the hot water heater, then a special mixing valve is not necessary at the hot water heater or shower.Another problem with the mixing valves is an increased failure rate due to impurities in many urban or rural water systems. High calcium content in water causes the moving mechanism in the pressure balance mixing system to fail, leaving the homeowner without water pressure in the shower or other fixture. Frequent disassembly, cleaning, and possible replacement is necessary in some areas where hard water is unavoidable. Some homeowners have had to install a home water softener or filtration system to help reduce failure of these mixing valves.#Increased fixture cost#Higher failure rate#Other added expenses such as water softenersThis is another example where the government wants to be our parent in a nanny state nation. The intelligent homeowner is not going to become injured by scalding if commonsense is used. However, because some dumb citizens might get hurt, the government is going to step in and force everyone by building code to update to more expensive bathroom fixtures or water heater safety devices and make us all pay more as well as over-complicate something that is frustrating enough, home plumbing.