Should the top and bottom water heater thermostats be set to the same temperature?

I did a quick google search and saw all kinds of differing opinions. for instance, this guy seems like he knows what he's doing:


and he said the top thermostat should be set to a higher temperature than the low one, but other places I've read said they should be at the same temperature.

my water heater's old, if that makes a difference. I didn't see a date, but the energy sticker had some reference to 1994. sorry I don't have more info; the thing's wedged back in a tight closet and hard to get to.

4 Answers 4


Setting the top element slightly higher helps the elements to be used evenly. If you set them to the same temperature, the bottom element will be the first one on every time, and frequently the only one used to maintain the temperature. If you set the top element too much higher, then it will be used most of the time, and the bottom element acts more as a pre-heater.

Having them used evenly will spread out the minimum time to replacement. But I wouldn't go through too big of an effort to change the settings on an old water heater. Whenever your elements do go, or whenever you decide to change the temperature, that would be the time to make this adjustment.

  • I am changing the temperature which is why I'm asking. What should the difference be? 5 degrees (F), 10? Thanks!
    – bmaupin
    Jun 29, 2011 at 19:41
  • When you change it, you'll be able to tell the temperature difference in the tank by when each element clicks on or off. If you can't get them exactly the same, and you're not using any water at the time, err on the side of having the top element activate slightly more. Cold water coming into the tank when water is running will reverse that balance.
    – BMitch
    Jun 29, 2011 at 19:47

The top element is always the first one on. In fact the bottom element does not receive power until the top thermostat is satisfied. I’m guessing that setting your top thermostat to a 150 would give you small amount of really hot water rather quickly, while setting the upper and lower thermostats evenly to a moderate temperature (115-125) would be your quickest way to get a full tank of hot water.


  • 2
    You should never set a residential hot water heater to 150 degrees. It is dangerous! Here is the time to get a third degree burn: 150 degree water for two seconds. 140 degree water for six seconds. 130 degree water thirty seconds. 120 degrees water five minutes.
    – Itsme2003
    Feb 26, 2019 at 7:23

Yes the hot water exits from top... I don't know who told him it exits from bottom that isn't even possible since the only tube going down that low in the tank is cold... You would never get good hot water if it exited from the bottom, it's simple thermodynamics, heat rises even in water therefore the most efficient way to pull hot water is from the top, if the top thermostat isn't satisfied the bottom will not come on... Remember to cut your power off before setting your thermostats, but there are many theories on what to set your temps on, I typically run my top 5-10 degree's hotter than the lower.. Some people do the same.. You can test what gives you solid heat for long time if you truly feel like just going through all of the hot water several times I suppose. I just kinda wing it, if your tank is too small then higher heat will give you longer time, but is dangerous especially if you have kids around.. There's really no right or wrong answer in my opinion..

Here's a link kinda showing the the basics of electric heaters..



I am a plumber and water hook up is on the top of the heater but the water that comes out through a dip tube that goes all the way to the bottom of the heater so the water you get to the faucet comes from the bottom of the tank not the top.

  • 3
    Hello, and welcome to Stack Exchange. This isn't true; hot water rises, and so the hot water output is from the top of the tank. The dip tube takes cold water in at the top of the tank and brings it to the bottom, preventing it from mixing with the hot water. Mar 10, 2018 at 13:31

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