Hot Water Above 120 Degrees:
Why Russ Measures It
Russ puts a thermometer under the hot tap at every house. At about one in five, the water came out hotter than 120 degrees F, the setting most safety groups recommend.
Russ measures hot water with a thermometer at a fixture on every inspection. At 47 recent inspections, it came out above 120 degrees F. That’s close to one house in five.
It’s a two-minute adjustment on most water heaters. It’s on the report because hot water is one of the more common burn injuries at home.
Why 120 is the usual target
The U.S. Consumer Product Safety Commission recommends setting water heaters at 120 degrees F. Above that, the time it takes for hot water to burn skin drops fast. A Portland report put it this way: temperatures above 120 increase the risk of accidental scalding, particularly for small children and older adults who may have slower reaction times. That report recommended a licensed plumber adjust the thermostat.
A water heater set on the high side often comes from the factory that way, or from a past owner who wanted more hot water out of a small tank.
How it gets turned down
On a gas tank, the temperature dial is on the gas valve at the front. It’s often marked with words or letters instead of numbers, so set it, wait a few hours and measure at the tap. Electric tanks have one or two thermostats behind panels on the side, under insulation, next to live wiring. Many owners call a plumber for those.
Tankless heaters usually have a digital setting on a control panel. Heat pump water heaters have a setting on their display.
Hot enough, but not too hot
There’s a second side to this. Water stored very cool can let bacteria grow in the tank, including Legionella. That’s why some plumbers keep the tank hotter and install a mixing (tempering) valve at the heater, which blends in cold water so the taps get water near 120. A licensed plumber can suggest which setup fits the house.
Shower valves are the other control. Most newer valves have an anti-scald limit stop that caps how hot the shower gets. Older valves often don’t.
The rest of the water heater
While Russ is at the tank, he looks at the relief valve and discharge pipe, the seismic straps, the venting and the age. The relief valve post covers the pipe that runs down the side of the tank, and the water heater age post covers how to read the label.
Real Inspection Photos
Hot Water Readings From Russ's Inspections
Hot water temperature readings from Russ's recent reports.
-
Hot water measured above 120 degrees F at a West Linn faucet. -
A water heater display set to 134 degrees. -
A reading close to 138 degrees at a bathroom sink. -
Kitchen hot water above 120 degrees F in Beaverton.
What Russ checks
He runs hot water at a fixture and measures it with a thermometer. He looks at the water heater, its controls, venting, relief valve and straps. He doesn’t adjust thermostats, open electrical panels on the tank or test the relief valve. Water above 120 degrees F gets a recommendation to adjust the setting, usually by a licensed plumber.
- Run the hot water at the kitchen sink for a minute and measure it
- Find the water heater’s temperature dial or display
- Note whether the shower valve has a temperature limit
- Ask whether anyone in the house is very young or elderly
- Measure again a few hours after any adjustment
Hot water above 120 degrees F came up at 47 of Russ’s recent inspections. The CPSC recommends 120 to cut scald risk. Turning it down is a small adjustment, and a plumber can add a mixing valve if the tank needs to stay hotter.
For the rest of the tank, the guide for agents on water heaters in Portland homes covers age, venting and straps. To set up an inspection, you can book online.
Water Temperature FAQ
