Water Heater Vacation Mode

[sparky472]

Got the new GeoSpring water heater installed this weekend. One of the features of the new heater is a "vacation mode" which you can program when you are going to be away - it will only heat the water to 50 degrees and the day before you come back from vacation, it will heat back up to full temp so you have hot water upon your arrival.

Neat feature. But I've always heard that setting the temperature below 120 creates a risk for legionella. So why would a feature like this be safe? I can't imagine that any litigation-averse major corporation would incorporate a feature that would pose a health risk... or would they?

 

[havasu]

My opinion with me being just as a layman and not a scientist is the fact that most municipal water supplies are already sanitized and chlorinated enough to kill most bacteria. Your cold water pipes are not heated and you don't worry about bacteria in them.

I think this is a nice energy saving feature.

 

[Chris]

I know for a fact that water districts have very very strict standards on bacteria so the water that comes to your house is very clean. Personally I don't know if this feature is good or bad but it couldn't be any worse than your cold water sitting in your pipes.

 

[Caduceus]

Maybe this will add some clarity to the issue and also explain my position on 'vacation' settings for hot water tanks. The air we breathe has bacteria and viruses as well as the soil and water around us. The concern is allowing a condition and environment to occur that promotes the cultivation of the bacteria/viruses. Most micro-organisms that we consume every day are in a low concentration and are easily combated by our bodies. The cold water that enters our homes is treated, but certainly not sterile. Here are a few OSHA parameters for water from their website.
Water conditions that tend to promote the growth of Legionella include:

stagnation;
temperatures between 20° and 50°C (68° - 122°F) (The optimal growth range is 35° - 46°C [95° - 115°F]);
pH between 5.0 and 8.5;
sediment that tends to promote growth of commensal microflora; and
micro-organisms including algae, flavobacteria, and Pseudomonas, which supply essential nutrients for growth of Legionella or harbor the organism (amoebae, protozoa).
More info is available on the interweb via health department sites, but consumption is less of a concern with legionella bacteria. It's when showering and the bacteria enters the lungs through water vapor.
If the water in a tank is cooled while on vacation, I usually recommend flushing the tank then firing it at a temp of about 145 degrees F. for about 4 hours then setting the temp back to 125-135 F. Of course opinions and procedures vary from state to state and this is just mine. Hope somebody can find some use for it.

 

[Caduceus]

There is a down side to leaving your hot water tank on when on vacation for several weeks. A few plumbers in my area found this out the hard way about 7 years ago. Luckily they all survived.
"Hydrogen Gas is produced by the chemical action within your water heater. The gas can accumulate in the water heater and/or water pipes if hot water has not been used for a period of two weeks or longer.

Caution: Hydrogen gas can be explosive under these circumstances. To prevent the possibility of damage or injury, if you have not used hot water for two weeks or more, or move into a residence in which the hot water system may not have been used for some time, turn on all hot water faucets and allow them to run several minutes before using any electrical appliances which are connected to the hot water system. This will allow any hydrogen gas to escape.

Caution: Since the gas is flammable, do not smoke, use an open flame, or appliance during this process.

If the water heater is turned OFF, the build up of gas would be eliminated. "