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legionares

radmix
radmix Member Posts: 194
After a recent outbreak of legionares at a local county building I have received several call from customers to turn the temp on there DHW tank to 140*. Would a simple UV light take care of the problem. I am questioning the efficiency of turning the temp up then mixing down the temps with cold water.

Comments

  • UV & Legionella

    UV is very effective if the bugs are exposed, the bulb is maintained, and the lens kept clean. However, Legionella use the cysts of one-celled animals as nurseries and like a Trojan Horse, that shell grants them a free pass past the UV. For full-blown protection, ultrasonic bombardment upstream of the UV will break apart the cysts to expose the bugs for steralization. A solenoid valve must be incorporated to halt flow if there's a power failure. I'd expect to see this type of system maintained about as well as we see folks maintaining grease traps!



    Heat pasteurization is our best bet. 140F is quite effective if the bugs are free-roaming and they experience a minimum of 20-minute contact-time. Won't kill them all, but keeps their numbers in check.



    Be sure to add a listed (means it has passed independent test to verify compliance) scald-guard device at the water heater's outlet. Follow that with a delivery-temperature test for end-user safety and have the homeowners and/or inspector sign off to cover your ****-sets.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    The added monthly cost of operation...

    is less than $2.00 per month.



    Is it worth it? As a survivor of legionairres disease, who is still feeling the side effects (lack of lung capacity) I can tell you that I would have gladly paid any amount of money to NOT have contracted the disease.



    it IS worth it.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • radmix
    radmix Member Posts: 194
    legionares

    $2.00 a month does not sound like a big deal if this is the cure to the problem. I can only assume the you are doing this to all of your DHW systems. This could also be a good selling point to customers if the others are not protecting there customers.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Absolutely....

    140 tank temperature with antiscald mixer down to whatever temperature the H.O. wants.



    The Europeans have been aware of this for a LONG time.



    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Kevin_in_Denver_2
    Kevin_in_Denver_2 Member Posts: 588
    Tankless?

    Since all the water in a tankless system is usually at 65-75 F, can we assume they are pretty safe?
    Superinsulated Passive solar house, Buderus in floor backup heat by Mark Eatherton, 3KW grid-tied PV system, various solar thermal experiments
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    You can never be too safe...

    The bacteria can thrive in places other than the DHW tank, i.e. hot tubs, cooling towers and any where that food, oxygen, water and ideal growing temperatures can be found.



    But as it pertains to DHW heaters, yes I think a tankless would be immune. The bacteria necessary can live in water temps as low as 40 degrees F. It's when they start thriving and multiplying that it becomes an issue. That occurs in warmer conditions, like petry dish conditions....



    The bacteria is omni present in water. We drink it on a daily basis.



    They can't survive in a highly alcoholed condition.



    I'll drink to that!!



    Make mine Bourbon :-)





    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
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