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We just got a new water heater installed in the basement, and the temperature in the 3rd FL shower is not hot enough for us. However, the temperature in the sink faucet on the 1st FL is fine and gets very hot, so that makes me think that perhaps the water heater temperature is fine. Would you suggest taking apart the shower handle, or would your first guess be something else? Shower handle is single Kohler shower handle.

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    do you have a faucet on 3rd floor? – jsotola Mar 25 at 17:43
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    @jsotola: I do, there's a sink there. Didn't think to check the temperature there, duh. I'll go check and report back. – David Mar 25 at 17:43
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    @jsotola: faucet temp is great – David Mar 25 at 17:51
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    Is the hot water pipe insulated? That would help. – Andrew Morton Mar 26 at 12:45
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Single handle shower valves normally have some way of adjusting the "all the way hot" stop of the handle. In many cases it's just a toothed plastic ring under the handle that can be moved to the next tooth or two to make the water hotter. This is meant to be a safety feature so even if the handle is cranked all the way on you don't get scalding hot water.

Your new water heater might not be set for quite as high of a temperature as the old one, so you're two choices are to adjust the shower or adjust the water heater. Note that adjusting the heater temp might make all the two-handler faucets hotter, so consider that.

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    Amazing! I didn't know the handles that this safety feature. I'll check tonight when I take it apart then. If you happen to have instructions or an image of this toothed plastic ring thing, just so I know what I'm looking for. I'll start googling as well. Many thanks. – David Mar 25 at 17:47
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    I wanted to keep it generic because you didn't say a lot about the shower handle in question, but here is an article from Kohler and here is a video of the Delta toothed ring that I am familiar with. The plastic ring on the Delta can break, allowing the handle to turn all the way around. It still works fine, but is annoying to set the right temp! – JPhi1618 Mar 25 at 17:55
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    really appreciate it, thanks. – David Mar 25 at 17:58
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It's possible the installer set the temperature low because they are worried about scalding, i.e. They don't want to be liable if you get scalded.

If you have all joystick 1-handle valves, those are thermostatic and will protect you.

Meanwhile, this installer may not know about legionella. The trouble in Flint surfaced a problem that was little known up to now: water heaters are breeding grounds for bacteria, particularly legionalla. You should crank the temp to 140 F for that reason alone, as that kills it.

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  • Cranking it up to 140 F will use an inordinate amount of electricity/gas (because rate of heat loss is proportional to difference in temperature, regardless of how good insulation is) and is almost certainly not needed for single-family residential use. EPA recommendation is 120 F which is sufficient to stifle growth of harmful bacteria unless you have other factors (common in commercial systems or large apartment buildings) contributing to them. – R.. GitHub STOP HELPING ICE Mar 26 at 15:26
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    Because heat conduction is proportional to the absolute difference in temperature, changing temperature from 120 °F to 140 °F will use about 3% more energy. Because of other losses, the total cost is probably a little greater, but not what I would consider unreasonable. – erickson Mar 26 at 17:26

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