I have an electric water heater. It has a top and bottom thermostat. In the summer I turn these down and in the winter turn them up. It's a real hassle because I have to unscrew the plates and then adjust the thermostat. If I get it wrong I have to do it again and would like to do micro-adjustments until I get it right. There are 2 modifications that I want to consider for this tank and need your input for.

  1. Is it possible to attach a knob on the outside of the tank that could control this thermostat without me having to unscrew that plate each time?

  2. Is there a way to control this wirelessly? I would absolutely consider a Raspberry Pi or equivalent project to get this working.

The purpose of this question is to find a way to easily way to adjust the two thermostats on the tank so the answers aren't limited to 1 and 2 above.

electric water tank


  • 3
    Two concepts - Legionella bacteria, and (external, easily adjusted) tempering valves.
    – Ecnerwal
    Commented Aug 8, 2020 at 1:59
  • 1
    Why do you ride the thermostat on your water heater? Commented Aug 8, 2020 at 2:18
  • For what reason do you adjust your water temperature up and down? Why not just keep the same water temperature year round?
    – brhans
    Commented Aug 8, 2020 at 3:41
  • I live in Phoenix, Arizona. Highs are 115 today. The cold water is fairly hot so the water heater temperature can be set much lower than in the winter when the temperature can drop to the 20s when it needs to be hotter.
    – Guy
    Commented Aug 8, 2020 at 3:42
  • @Guy -- it sounds like the thermostat isn't being very thermostatic then :P Commented Aug 8, 2020 at 3:49

2 Answers 2


Making it easy to adjust is defeating the purpose of the cover. But since this is what you want, here is a way to do is make it easier to adjust without removing the cover.

  1. Replace the adjustment screw or bolt with one long enough to stick out of the cover approximately 1/2 in. The screw head type could be hex, flat blade or Phillip head. A hex nut could be used on the lower thread to clamp down the adjustment knob with the upper part extending out past the cover.
  2. Where the screw would protrude through the cover, drill out a 1/2" hole in the cover so the screw can protrude through.

That said, It is strange that you are trying to set an exact/precise temperature. I would just mark the two points that you want to set for winter and summer. The installed thermostat is not designed for setting to a precise temperature.

  • Thanks @Programmer66 - it's not so much that I want an exact temperature it's more that (1) I often get it wrong (too hot/cold) and (2) I would be able to gradually adjust it as the season changes.
    – Guy
    Commented Aug 8, 2020 at 3:38
  • 1
    Why don't you just set the temperature you want on your faucets @guy? Commented Aug 8, 2020 at 7:48
  • It costs money (and also not environmentally friendly) to constantly keep the tanks at a high temperature when that is not needed. That's only needed in winter.
    – Guy
    Commented Aug 8, 2020 at 17:01

That's not a thing you want to do. You need to keep the heater temperature around 140F in order to stop breeding bacteria, including legionella. See the discussion here.

This legionella issue is relatively new and not widely known yet, but it is legitimate.

  • Thanks Harper. This got me to read the Wikipedia article on this as well. It looks like the growth and ideal growth ranges according to that are 77 to 108 F. I live in Phoenix AZ. For several months of the year I think that the cold water coming in from the street can fall in that range. Also, every single of the 1m swimming pools in AZ will be in that range. While you may well be right that the water heater in that range would exacerbate the problem I don't think that this is something we can get away from in this climate. Thanks for the answer!
    – Guy
    Commented Aug 9, 2020 at 14:29

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