My water heater is set at the default 120F temperature, I bought it 4 years ago brand new, and I remember for the first 2 years of use I would turn my shower faucet valve (located upstairs) to the middle (90 degrees) for a nice hot shower. Now I must turn the faucet far past the middle (130 degrees, towards the direction of hot) to get the temperature I used to be getting when it was new. I flushed out my tank fully and saw a lot of sediment come out of the hose but it still didn't help the unit perform like new.

I could set the water heater temp to "A" (130F) but the most energy efficient method is to keep it at the default 120F so I rather not do that.

Any ideas?

  • If you feel that the water heater is malfunctioning in any way start a warranty claim from the merchant you purchased it from. Most brands have at least a 5-7 year guarantee.
    – ojait
    Jan 14, 2021 at 0:18
  • Why do you think it is your water heater? The sediment is probably the anode and it should be replaced but some sediment mace have affected the valve. Get a temp probe and check the water heater water temp it is probably closer to it’s set point than the valve.
    – Ed Beal
    Jan 14, 2021 at 0:19
  • 1
    You may be mixing up two different things: Temperature of hot water and mixing of hot & cold water. Unless your cold water is always exactly the same, an anecdotal comparison just doesn't work. Get a thermometer that can safely measure up to at least 140 F. Run hot water from a faucet until it is as hot as it gets and measure the temperature. That temperature becomes your baseline for comparison. It is much less than 120 F then you may have a basis to complain to the manufacturer. It may be right on target and the real problem either flow rate (if the hot is clogged up) or how cold Jan 14, 2021 at 0:25
  • the cold water is. Particularly, right now is the winter in the northern hemisphere. If your cold water has been getting colder for the past couple of months due to natural cooling, a straight 50/50 hot/cold mix will also have gotten colder yet may be the same as January 4 years ago. Or it might not. But measuring by hand at a mix setting on the faucet is not a scientific/accurate way to figure out hot water heater performance. Jan 14, 2021 at 0:26
  • 2
    Yeah, your data collection has fatal flaws. You are presuming that nothing has changed except the water heater - presuming the shower knob hasn't changed, the ambient temperature the pipes run through hasn't changed, etc. You need to eliminate more variables before you can attribute a cause. Jan 14, 2021 at 0:58

3 Answers 3


Like someone else said, run a hot water tap for a while and measure the temp. That's what your WH is supplying. If at about 120 or so, the WH is doing its job. If your shower has an automatic mixing valve, the cartridge may need to be replaced. We had the opposite problem....the mixing valve wouldn't mix enough cold water even on the coldest setting to make the shower tolerable....it was way too hot. Replacing the mixing cartridge solved the problem.

Bottom line, it's either the WH or a mixing valve (if you have one).

  • Yes mixing valves are a common problem and everyone forgot to mention to replace the anode. that sediment in the tank was probably from the anode or a vast majority of it was+ And could be the cause of a mixing valve failure.
    – Ed Beal
    Jan 14, 2021 at 14:17

Is the lowered temp only at one fixture or throughout the house? If there is indeed a temperature drop in the water from the water heater throughout the house, I would suspect a failed element (assuming the water heater is electric) or a bad thermostat.

Get the service manual for your make and model and test the element(s ) and the thermistat(s), if electric.


In the word's of the late Jimmy Durante "Nothing lasts forever". This is true for all appliances. And while taking measures like flushing sediment from the tank is a great way to extend the life of a water heater it can't maintain a like new function.

Flushing hard water sediment and other deposits definitely extends the working life and saves energy of the water heater. The problem is that only the loose deposits are flushed out with water. The scale that isn't loose is built up and attached to other parts in the tank.

If you have an electric heater minerals are coating the heating element and can't be removed any other way unless an acidic solution is applied.

The bottom of a gas fired heater has a layer of scale that is tenaciously secured to the metal and only brakes off when it becomes too thick. Again the acid solution can only remove it.

So flushing only removes loose deposits while more is still coating the interior. This is part of the reason the heater is working poorly.

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