Water heater - one notch cold to hot

Found this on a Canadian CDC website:

* 70 to 80 °C (158 to 176 °F): Disinfection range
* At 66 °C (151 °F): Legionellae die within 2 minutes
* At 60 °C (140 °F): Legionellae die within 32 minutes
* At 55 °C (131 °F): Legionellae die within 5 to 6 hours
* Above 50 °C (122 °F): They can survive but do not multiply
* 35 to 46 °C (95 to 115 °F): Ideal growth range
* 20 to 50 °C (68 to 122 °F): Legionellae growth range
* Below 20 °C (68 °F): Legionellae can survive but are dormant

So, at 140 degrees F to the shower heads and faucets, it takes 32 minutes to kill it. Not going to happen in my household...

 

Where is the legionellae going to come from? You can sanitize your system after doing work. It does not come back from spontaneous generation.

 

I don't think it's as big an issue at the taps or showerheads, since they are not warm very long. But the water heater could house bacteria for a long time at the set point, and doesn't completely flush out with each use.

 

When going on vacation depending how long if it is wiser to just shut it and relight it when you return

Unlike a boiler a water heater has one safety device the T&P a Boiler has high limit and LWCO plus either a safety or a relief valve plus operating controls