I quietly adjusted our water heater’s dial three weeks ago. I didn’t tell my wife or my 3- and 5-year-olds about it. No one has complained that they didn’t have enough hot water, or that the water wasn’t hot enough.
I made a small change to the dial on our water heater, but now the water temperature at our sink in the basement is down from just over 130°F to around 120°F. By lowering the water heater temperature 10 degrees, I am making it less likely that my kids will scald themselves.
My water heater’s dial said “hot,” but my thermometer disagreed
The markings on the dial are only approximate
We have a 75-gallon gas tank water heater made by Bradford White, located in our basement. It has a control on the front called an ICON System. There is a red knob on the ICON System that can be turned from Low, to three dots, each evenly spaced from each other, to HOT, and beyond that, to A, B, C, and VERY HOT.
In the manual for the water heater, Bradford White estimates that the HOT setting on the dial is about 120°F. They also state that the water heater dial settings are approximate. On our water heater, the dial setting was just under HOT, so I figured that our water heater was set to about 120°F.
I ran the sink in our basement, the one closest to our water heater, for one minute, and then used a meat thermometer to measure the water temperature. Every time I tested the water, the temperature was between 130.1 and 130.3°F. So even though the dial was set to just under HOT, the water temperature was still 10 degrees hotter than it should have been for HOT. As I keep learning from my cheap multimeter, don’t take a label at its word, measure first.
A tiny turn of the knob dropped 10 degrees
How far I actually moved it
Before the adjustment, the knob on our water heater was set to about 7/8 of the way from the third dot to HOT. After the adjustment, it is about 3/4 of the way from the third dot to HOT. It’s a very small adjustment, and you can barely see the difference in my before-and-after photos.
I ran the same sink for a minute and checked the temperature again, using the same thermometer. The water is now about 120°F. If you have the same control, consider it more of a fine-tuning knob: adjust it, test it, and repeat until you achieve the temperature you want.
Why nobody in the house noticed
The shower valve just adds less cold water
No one showers in 130°F water. Most of us like it around 105°F, so we add cold water to the hot water in the shower. With the 130°F water in the tank and our 55°F well water, we mix about two parts hot to one part cold to get there. With the 120°F water, we mix about three parts hot to one part cold.
The water feels the same coming out of the shower. We just use up our hot water a bit faster.
How big a difference is it? As a theoretical example, our 75-gallon tank at 130°F can produce about 112 gallons of 105°F water. At 120°F, that’s more like 98 gallons, about 13% less. That’s still more than enough hot water to give our kids baths and take showers one after another. We haven’t gotten a cold shower yet, and we don’t get spots on our dishes.
Scald safety with two small kids was the real reason
Ten degrees changes how fast hot water burns
I’m all for saving energy, but with a couple of kids, it made my decision a lot easier. According to the U.S. Consumer Product Safety Commission, it takes about 30 seconds of exposure to 130°F water to cause a third-degree burn. At 120°F, it takes about 5 minutes. Most of the tap water scald injuries occur in children under the age of 5 and in older adults. I have a 3-year-old in the house who falls in that category, and a 5-year-old who just aged out of it.
Thirty seconds isn’t much time to realize that your child has placed a little hand under the wrong tap. Five minutes is a lot of time. It’s the same reason that I keep the space heaters off my smart plugs come winter time: small adjustments, large consequences.
The savings are real, but my gas bill can’t prove them
One gas meter feeds six appliances
The Department of Energy’s Building America tips state that if you turn down your water heater 10 degrees, you’ll save about 5% in water heating energy. This is due in large part to standby loss, the heat lost by a water heater to the basement when not in use.
We share a gas meter for our furnace, 2 gas fireplaces, dryer, garage heater and stove. It’s November. Any savings in our water heater will be overshadowed by our furnace usage.
I’ve worked in HVAC. Legionella bacteria like lukewarm water. The common practice in commercial buildings is to store water at 140°F. In a home with regular hot water use, 120°F is low risk. If you have someone in the home with a compromised immune system, store water at a higher temp and use a thermostatic mixing valve to deliver 120°F at the tap.
Trust the thermometer, not the dial
The dial on the water heater is an estimate. Mine said we were below HOT, and we had 130°F water coming out of the tap. A minute with a meat thermometer at the closest sink taught me more than the label did.
Check yours this weekend. If it’s over 120°F, turn it down a little on the dial, check it again, and see if anyone notices. Add it to your cold-weather checklist along with the batteries I check before winter.