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Home Safety, Mobility & Setup Guides for Adult Children

Water Heater Temperature Setting

By Aging Parent RescueSeptember 1, 20262 min read
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Temperature scale showing 120 and 140 degrees Fahrenheit with the time each takes to cause a serious burn
120°F

Thermostat setting at the tank. Aging skin is thinner and reacts more slowly, so the safety margin is smaller.

Widely recommended by burn-prevention programmes; also the usual anti-scald design point.

The gap is reaction time120 F140 FcoolerhotterAt 120 Fseveral minutes to a burnAt 140 Fabout five secondsDo not set below 120 F – stored water needs the temperature.Check with a thermometer. Dial markings are often wrong by ten degrees.
A factory setting of 140 F gives about five seconds. 120 F gives minutes. That difference is entirely reaction time, which is exactly what is reduced here.

At 140°F — a common factory setting — a serious burn takes about five seconds. At 120°F it takes several minutes. That gap is entirely reaction time, and reaction time is exactly what is reduced in the people this site is about.

Two places to control it

  • At the tank. Simple, free, affects the whole house. Gas heaters have a dial; electric usually needs a panel removed and the power off.
  • At the fixture. A thermostatic anti-scald valve at the shower or basin holds a set temperature even if someone flushes a toilet. Better protection, but a plumbing job.
Do not go below 120

Turning the tank much below 120°F can let bacteria grow in stored water. 120 is the balance point, not a floor to keep lowering.

Check it with a thermometer, not a hand

Run the hot tap for two minutes, fill a cup, measure. Dial markings on water heaters are frequently wrong by ten degrees or more.

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