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Legionnaires Disease and Hot Water Tank Temp

SpeyFitter Member Posts: 422
I was talking with a local boiler rep today and we were discussiong hot water tank temps. He told me according to what he heard recently, that "apparently" ASHRAE would soon be re-writing the whole speel about keeping a hot water tank at 140 degrees to kill of Legionnaires and recommending 120 degrees, as there has never been one iota of proof of anyone having caught it due to their interaction with domestic hot water, or something along those lines.

Have you guys heard anything along those lines?
Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber


  • That would be funny if....

    not for the fact that it constitutes blantant ignorance of the facts. Legionella survive quite well at 120F as has been established repeatedly (do a bit of research or simply Google "Legionella + water heaters" or "Legionella + hot water" ) by the scientific community.

    Here's but one of thousands of articles available; [url=http://www.legionella.org/100960699-1.pdf]http://www.legionella.org/100960699-1.pdf  
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Looks like an overwhelming "body" of evidence to me....

    As a survivor of LD, all I can say to not contracting LD from a low set water heater is BUNK!

    I am very lucky to be alive.

    I actually heard something to the contrary, that one of the code authorities was adopting 140 as the minimum set point, with antiscald device on the outlet set to 120 degrees F.

    Time will tell, but one thing will remain the same. LD is a deadly disease, and it CAN be controlled with higher temps. Look to the Europeans for guidance. They've been there and done that.

    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.
  • D107
    D107 Member Posts: 1,849
    'Periodic Burnoffs'?

    What are your opinions about a European HW tank I've heard of on another site with an electric element that,

    once a week jacks up the tank temp for awhile to kill off the bacteria.  Low, regular storage temps and periodic

    "burn offs". of course I prefer 140 degrees for the increased capacity as well.....
  • ttekushan_3
    ttekushan_3 Member Posts: 958
    Hi Mark

    I remember your posts of your LD experiences vividly. Your posts alone changed how I advise clients from that point on. The fact that it is an inhalation problem and that the most vulnerable among us have issues with lungs/brachia, to recommend low water temps is simply irresponsible.

    140° water temps aren't ridiculous. Given a choice between a mild scald from 140° water (assuming no tempering) and a miserable illness/death, I'll choose the former. I'm strange that way.

    I always used 140° anyway for the dishwasher and winter cold water tempering. I never could determine any difference in gas usage regardless of water heater temperature.

    I can't put my finger on the study right now, perhaps others here know of it (I saw it on the Wall to begin with): It determines that fuel consumption difference for water heating @ 120° vs 140° with a standard water heater to be quite small.

    Anyway, we like you around here Mark. Keep that water heater turned up!

  • added energy costs 120F vs. 140F


    I had the same question years ago while researching these issues. What looks like a simple exercise becomes quite complicated as you move around the storage vessel and even more so if it has an uninsulated bottom for its burner chamber. Heat losses vary depending on lots of circumstances & I'm not an engineer, so I turned to the engineers at Bradford White for help. According to them, the cost difference is a whopping $12.00 per year. Fuel costs are higher now, so that would no doubt be a bit higher. However, it seems crazy to me to risk life needlessly and absolutely amazes me that, in spite of all the evidence, our plumbing codes in the US are more influenced by lobbyists than common sense.

    The solution is simple: heat pasteurization coupled with scald-guard devices. D'OH!

    But, the reality is this: the changes required (while simple, cost effective, and healthier for the public) would cause an increase in the construction cost for homes and that means it's not going to make it from introduction to passage and then into print in the national plumbing codes.

    CIPH in Canada adopted 140F and scald-guard protection several years ago.
  • MarkPFalade
    MarkPFalade Member Posts: 68
    When you say

    "Scald guard protection" are we talking a mixing valve at the tank with anti scald fixtures or 140* straight to the system with anti scald fixtures?
  • not rocket science - it's applied science

    with a healthy dose of common sense mixed in. Here's a link (part II) to the resolution that fell on deaf years years ago. When you mention this to folks in other countries - as I did at ISH in Germany - they look at you as if you're from Mars and scoff at the notion our systems remain unprotected. As one vendor in the water treatment hall said "What? Are you nuts?!?" That's when I broached the subject of open dual-use potable/hydronic systems and also the exact moment he refused to talk to me anymore. He didn't let me explain I am opposed to open systems - he turned and walked away.


    It's almost too simple: cook the bugs in storage at 140F or higher; ASSE 1016 or 1017/1016 (combo) thermostatic mix valve at the outlet; constant circ (I use gravity for mine); and, finally, ASSE 1016 T/P for all bathing modules and ASSE 1016 T or P for all other points of use where human contact will be possible.

    OK, so why treat more than just the tank? Well, for starters it takes 20-minutes of contact-time at 140F to kill off most (not all) of the free-roaming Legionella - that's free-roaming, not the bugs embedded in biofilms or encased in cysts of one-celled critters (much like a Trojan Horse) where they set up nurseries - see Global Pipe for video of Legionella Sero Group 1 bugs bursting forth from cysts or the Watts video "Scalding - Danger Lurks" (it's free from Watts) that includes footage from Global Pipe's video. So, the reality is some of the bugs riding the cold water wave will move on through the water heater before sufficient contact time for suppression of colonies and they'll seed the biofilms in the distribution system where they'll breed freely. That's where the need for constant circulation comes into play at temps of 133F or higher. The final step is the final step-down via the ASSE faucets or valves.  

    So, pick a number from 1 to 35,000 or higher (community acquired Legionella cases annually with a 3% to 15% mortality rate) or 100,000 thermal scald burns seeking medical help each year in the USA with 35,000 of them being children and, on average, several dozen deaths to go with and then stop to wonder why our codes officials have chosen to ignore these issues while allowing 'standard' plumbing codes to continue without addressing these easily altered statistics - if only they would act.
  • TonyS
    TonyS Member Posts: 849
    OK but what protects the cold water line

    .they also have tanks in line. softners, neutralizers and filters. I cant agree with you that we need another law to force a couple hundred dollar increase in water heater installs.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    edited November 2009
    The bacteria is omni present....

    Meaning it is in some cold water. Contracting LD is a matter of health condition during exposure, bacteria concentration, and the method of induction. If your immune system is depressed, and the bacteria concentration is high, and you inhale it into your lungs, you will contract LD.CDC did a random blood test and 90% of the people tested showed that they had been exposed to the bacteria. They probably drank it. It when the bacteria are in warm conditions, and have access to food and oxygen that they become prolific and thrive and increase to the point that they become problematic. In fact, they can't survive extremely cold water (less than 40 degree F), hence you don't hear of many cases where well water is being drawn out of the ground with real low incoming water temps.$200.00 more is not going to cause the collapse of the new housing market, or even the retrofit market for that matter. How much is a life worth? How much longer might some parents live if not exposed to LD? What is THAT worth?

    I guess we can agree to disagree on that point.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.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Thanks Terry....

    The only good thing about contracting LD, is that there are no known cases of contractees contracting it a second time. At least, none documented.....

    Trust me, I keep ALL of my and my relatives water heaters set to no less than 130 degrees F, and no hotter than 140.

    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.
  • TonyS
    TonyS Member Posts: 849
    What about tankless units

    since the contact time is 20 minutes would there be any sense to increasing outlet temp to 140?
  • bill_105
    bill_105 Member Posts: 429
    Not to digress at all

    Those injection pumps used to create hot water immediately at the tap always struck me as odd. All of this is to avoid a Recirc. loop. If you want a cold glass of water it probably came originaly from the hot. Now comes the LD issue. Home Depot has them now.
  • mars_6
    mars_6 Member Posts: 107
    My personal water heater

    After having heard what ME went through with LD I personally keep my water heater at 160 deg. To hot some might argue but my kids are older, and I appreciate the additional hot water for showers and baths. energy efficient? No but am I killing any bugs in my system yes. You might ask why do I keep the temp so high. The answer is simple my wife has Hep C and has a compromised immune system to deal with. This is a simple way to deal with a real problem. Sincerely Matt Rossi      
    Matt Rossi
  • TonyS
    TonyS Member Posts: 849
    Bill brings up a good point

    considering the injection pump he is talking about is Grudfos, which is European. Do they use those units in Europe?
  • Dave Yates (GrandPAH)
    Dave Yates (GrandPAH) Member Posts: 281
    edited November 2009
    cold water vs hot water

    Good question. One of the things that really hit home with me at ISH in Germany while visiting the water treatment hall, was the manner in which they can ensure a bacteria-free system by first utilizing ultrasonic bombardment to shatter cysts of one-celled animals where Legionella have set up nurseries, which then exposes the bugs to the next step - UV sterilization. They do this where potable water first enters the building.

    Not exactly a solution for what we're discussing, but thought their from-the-start treatment might be of interest.

    For whole-building eradication of Legionella and this treatment is affective for long-term stagnant branch lines with 100% residual kill-rates, they were using Chlorine Dioxide treatment systems injected into the incoming cold water line. (The 2% to 4% Chlorine in our potable water systems has no affect on Legionella and cannot penetrate biofilms. Chlorine Dioxide, on the other hand, is very affective and does penetrate biofilms.)

    Legionella colonies in potable cold water lines (residential systems) exist and colonize the biofilms, but the relatively low water temperatures tend to keep their numbers in check. This is the main reason why plumbers are required to flush potable water lines after making repairs - to flush out the biofilms now disturbed and suspended in the water.

    Water heaters are listed as an amplifier, meaning that under the right circumstances they offer an ideal environment for bacterial amplification. The distribution network and points of use all drift through ideal amplification temperatures, have stagnation, food sources for the bugs, and ideal pH. That's why I believe treating just the tank is only part of the required solution.

    Plumbing codes were instituted during an era when thousands died each year - often within 24-hours - from polluted potable water systems. They were founded upon the most noble of causes - to protect the health of the nation by establishing basic standards for maintaining sanitation.

    But, you need not lose any sleep over the added cost. There's virtually no chance we'll ever see these common-sense changes to our plumbing codes because lobbyists - with very deep pockets - will ensure none of these changes will make it past the proposal stage. Mark & I know this from our first-hand experiences.
  • TonyS
    TonyS Member Posts: 849
    edited November 2009
    Hot and Cold

    So if 140 is whats needed to kill the Bacteria,what temperature was found to be the ideal breeding range. My well water is 57 incoming, at what point does the ideal environment start to reverse itself. Or does it just keep getting worse the hotter it gets until it reaches 140. Thanks for the info
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Between 70 and 120 degrees F

    Above 130, the bacteria count falls significantly.

    Although, it has been found in hospital systems where the storage tank has been kept at 180 degrees F...

    In lesser quantities, but it survived, nonetheless.

    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.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    You drink Legionella every day....

    Most everyone does. It is in the dirt, and consequently, it is in the water.

    If you want a drink of cold water, you'd best keep a pitcher of water (or beverage of your choice) in the refrigerator.

    Those circ systems DO save on wasted water, waiting for the hot water to get to the furthest reaches of the system, but if improperly controlled, can waste energy.

    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.
  • Dave Yates (GrandPAH)
    Dave Yates (GrandPAH) Member Posts: 281
    edited November 2009
    cool to hot!

    Here's an interesting tidbit I learned over the years of research: below 55F amoeba consume Legionella bacteria, but above 55F the roles reverse and Legionella are absorbed by the amoeba only to find themselves being consumed from the inside! Hence the cyst of an amoeba becomes the Trojan Horse nursery. Its outer shell serves as a protective layer until so over-stuffed, the bacteria literally burst forth. (Global Pipe video)

    So, 55F seems to be the starting gun in the relay race of replication. As temps warm to 80F, the bacteria begin to produce more rapidly and at 98.6F find themselves in an ideal environment for rampant reproduction (human lungs). 110F is simply a nice day at the beach where these promiscuous beasties enjoy multiplication. At 120F, they begin to feel a tad unreproductive, yet continue to live quite well. At 133F, the death-march begins for free-roaming bugs and at 140F, it takes 20-minutes of contact time to kill off many of the free-roaming buggers.

    Interestingly, Danfoss commissioned a study years ago to determine if 180F 15-minute flushes really killed off and sterilized potable hot water lines - as has often been touted as the 'cure' for systems that test positive for Legionella. While that tended to suppress the cultures, they determined that cultures of Legionella survived in the outer fringes of the biofilms and recolonized the systems - as has been the case in numerous facilities where super-heated hot water flushes had offered only temporary abatement. Global Pipe's study also confirmed the same results.

    So, the deal is this: you simply cannot eradicate this bug via elevated temperatures, but you can keep its numbers in check and provide safety for the majority of the public. Immunocompromised patients, aids patients and others who are extremely susceptible must exercise caution to remain safe.

    Folks using nebulizers must be wary of the water source when cleaning and refilling the humidifier reservoir. One case I recall centered on a nursing home where the attendant had cleaned and refilled the nebulizer reservoir with warm tap water. Most pneumonia deaths, like his, are not tested for the root cause and pneumonia is one of the leading causes of death for elderly folks.

    For my parents, as their health declined, I installed ASSE 1016 T/P certified scald-guard valves and then raised the storage tank temperatures. Good thing too. Dad fell in the shower on Memorial day two years ago and Mom did not find him for about 30-minutes. He was unable to get himself back up. When folks fall in a bathing module, they often end up grabbing the one thing they instinctively know about - the faucet - and there have been documented deaths of elderly folks who essentially cooked themselves because, like Dad, they were unable to move out of harms way after falling. Mike & I had to respond and extricate Dad from the shower. He was mightly embarrased, but alive because his shower valve was properly installed and adjusted. He passed a bit more than a year ago, but not from pneumonia.
  • TonyS
    TonyS Member Posts: 849
    What about copper pipe

    copper is somewhat bacteriostatic like silver. Has there been any study done on plastic water pipe as compared copper?
  • hot_rod
    hot_rod Member Posts: 21,851
    new controls for solar

    have OTD "option thermal disinfection" programs. I've been told France, Germany, and Spain now require a 30 minute period of 140F every 24 hours on solar tanks.

    Our next batch of controls will include this feature, you can block it.. Although it is still not a perfect function as it fires the top coil via a back up boiler source, or top electric element. It is possible the bottom portion of the tank may not get to 140F. But it does address the codes in those countries. It also includes a monitoring and starting delay options in the program.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Supresses bacterial growth...

    But does not stop it. See noscomial infections in hospitals and the like.

    The problem with plastic, non barrier tubing is that it allows the bacteria one of the essentials it needs to survive, that being oxygen. Metal pipes can't diffuse oxygen thru the walls.

    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.
  • biofilm coating negates copper

    Studies clearly indicated that copper's bacterial benefits are neutralized once there's a biofilm and just the outermost fringe of the biofilm - where direct contact with the copper takes place - is affected. If you're a plumber, you know it doesn't take long for biofilms to form in potable piping.

    One treatment system we haven't discussed is copper/silver ionization and it too offers 100% eradication with residual kill.

    So, that leaves us with heat pasteurization; Chlorine Dioxide; copper/silver ionization; and untrasonic bombardment coupled with UV sterilization (for new uncolonized systems).

    What's the one thing we all have that's already in place? Heat pasteurization. All that's needed, and should have been added to our codes long ago anyway, is ASSE certified scald-guard devices. ANSI codes already allow for a 30F rise above the tank's setting to accomodate stacking issues, so that so-called safe 120F setting can actually be code compliant with 150F being discharged to points of use.

    Bradford White has two new hi-cap gas-fired tanks that come equipped with an ASSE T-mix valve. Nice to see a manufacturer stepping up and being proactive.
  • TonyS
    TonyS Member Posts: 849
    Heat pasteurization

    The problem with that method is it only does the hot side. There are alot of systems with neutralizing tanks, contact tanks, filters, ect. that are siting in rooms at ideal breeding temps. It would seem to me that a better way would be to treat the problem as it entered the home, both hot and cold lines. I have installed many UV lights but am unfamiliar with this ultrasonic device. Do you have any info on it? Thanks
  • Gotta love Google!

    A quick Googling: http://www.hielscher.com/ultrasonics/water_disinfection.htm

    Agreed, but you need to start with a pristine system. The incoming line needs a solenoid valve to immediately halt water if power is lost. I agree with you re the cold and those tanks. However, the rampant growth will always be on the warm side of the residential distribution system and that's more easily and economically treated.
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