Best Way To Mitigate Legionella?

[alreadyinuse]

We have a new Rheem electric water heater with 2 elements.

We have temperature set to 130F
If we don't use hot water for hours, we notice that the lower temperature reading can be 113 F for hours until hot water is used. The upper temperature reading in the tank generally remains near 130F.
Appears that the heater design turns on the upper element only during periods of non use. I am disappointed with this design. I'd prefer that the entire tank be maintained close to the set temperature during periods of non-use so we can control risk of Legionella.

During the summer on some days, we may take shower in morning and not use hot water again for nearly 24 hours later. Maybe longer on weekends.

What can we do to best handle Legionella risk? Convert to a 1 element electric water heater, if there is one for a residence?

Is there a brand of water heater that would maintain the set temperature of all the water in the heater during 20 hours of non-use?

I suppose we can turn our water heater up even higher to 140 and install a mixing valve. I am not so much a fan of this in the event the valve fails. 140F is too hot. We don't want to be going to hospital.

Not sure if we have space for converting to a tankless gas heater.

thank you in advance.

 

[CountryBumkin]

Have you read this publication http://www.cdc.gov/legionella/index.html ? Most of the "prevention material" provided at the CDC site is centered around Hot Tub use. About the only thing a homeowner can do is disinfect the water supply at the point of entry (such a chlorine injection with carbon filter system).
Or for $43 you can get the full ASHRAE Guideline 12-2000

 

[Sponsor]

 

[alreadyinuse]

Have you read this publication http://www.cdc.gov/legionella/index.html ? Most of the "prevention material" provided at the CDC site is centered around Hot Tub use. About the only thing a homeowner can do is disinfect the water supply at the point of entry (such a chlorine injection with carbon filter system).
Or for $43 you can get the full ASHRAE Guideline 12-2000

I have looked at this reference which recommends setting temp to 140 F at heater and removing scale and sediment and dead plumbing legs.

https://www.osha.gov/dts/osta/otm/legionnaires/hotwater.html

 

[alreadyinuse]

Thank you I will look into this.

I guess I should have used the Word prevention in subject. I would like to PREVENT Legionaella rather than implement strategies to resolve an existing problem with Legionella.

 

[CountryBumkin]

That OSHA link was good.
The recommendations to keep the water hot and not let it sit stagnant (keep the water moving) are good preventative measures. If you can add a hot water recirculation line/pump and set it run often that should take would be good too. And, as I mentioned above if your on a well you should have some type of water treatment system (like Chorine, Ozone, ultra-violet light, etc.). There's some good stuff on that over here https://terrylove.com/forums/index.php?forums/water-softener-forum-problems-installation-and-r.22/

 

[Reach4]

Well or chlorinated city water?

 

[Jadnashua]

Something doesn't seem right here...on most electric WH, the top element comes on first to get you some hot water immediately and when the rest of the tank has cooled off, but once the top of the tank is warm, it switches to the bottom element which should keep the whole tank hot because of convection. They do not (in most WH) ever run both elements at the same time. What you are describing seems to imply the top element is not switching the bottom one on once it reaches its setpoint. This would also limit how much hot water you had, since the top element is much less efficient at making the whole tank hot than the bottom one. Maybe a problem with one of the thermostats, or the wiring.

Code most places requires a tempering valve to limit the tank's outlet to 120-degrees, so having it at 130 or even higher would require one where I live.