Hot Water Heater temp setting.....no mixing valve.....how real is legionaires?

GFarra

Hi Everyone,

I have been lurking here for a while and have found this site and the people here to be incredible helpful. Let me start by saying I am a homeowner. Plumbing, heating, and electrical is not DIY IMO .

My DWH is your traditional Bradford White 75 gallon gas fired heater. I keep reading posts here about setting the water temp at 140 to ward off legionaires bacteria. My Bradford uses the Honeywell thermostat. I also do not have a mixing valve at the hot water heater.

I have the thermostat set at the "hot" mark which I is supposed to be 120 degrees (per the manual). I used to have it just shy of the "A" setting but my wife and I felt the water was too hot and we were worried about getting scalded, so i dialed it back. But now I'm thinking I could be setting us up for a problem.

My tank does have a circulation loop to my master bathroom which is gravity fed, no pump, and it works. We have instant hot water in the master all the time.

So.....how real is this bacteria threat in hot water heaters? I hear about this on the news but it always seems to be in cooling towers of high rise buildings. I'm almost 50 years old and I have never had a hot water heater set up with a mixing valve.....honestly it sounds like it should be mandatory.

Thoughts?? Thank you, George

GFarra

I would also like to add that I am on municipal water.

Thank you , George

hot_rod

This sums it up nicely.
https://www.healthline.com/health/legionnaires-disease#causes

GFarra

hot_rod,

Thank you for the information. I will discuss having a mixing valve added to my hot water heater with my plumber.

I'm surprised that the things arent set up like that from the begining.

George

hot_rod

GFarra said:

hot_rod,

Thank you for the information. I will discuss having a mixing valve added to my hot water heater with my plumber.

I'm surprised that the things arent set up like that from the begining.

George

There are legionella codes and products being developed. Until it is required by code or health officials it usually is not added to the product.

Some brands and models of water heaters have included mixing valves with the product, high temperature operation like the Bradford white CombiCor for example.

Public buildings will probably be mandated to require anti legionella protection first. We need a clear code to establish the requirement.

ASHRAE 188 is a start, NSF and other bodies are working on a more defined code verbiage. Elevated temperature, above 140F is generally agreed to eliminate bacteria growth in the tank.

Questionable still is how to protect all the piping, supply tubes etc in a typical system.

archibald tuttle

wow, another 'controversial' thread. I notice @hot_rod that the informational primer you linked does not really list hot water heaters as a source (and i've been asleep at the switch having apparently missed ongoing discussion of the possibility here).

And it doesn't seem to list, for instance, private showering as a significant vector behavior which would be one way to plausibly inhale droplets from your own hot water system. Or explain why public showers are a vector. I always divided this risk in my mind between closed and open systems and associated showering with water emitted from a closed system that is drained away rather than stored so I never thought of it as serious vector. I had generally associated outbreaks with open systems, like open cycle condensor cooling, whereas you don't have an entry source for the bacteria into closed systems that might otherwise have suitable temperatures for propogation.

I get hottubs kind of in the same vein (turned mine off for the summer, it's not very volatile and still treated but i'm going off to empty it which i've been meaning to do anyway) Although generally i think you get chlorine/bromine vapor more than water droplets from the hottub.

There is probably plenty of research on this and I could go google it, but if there are industry white papers on the prevalance in closed hot water heaters of varying sorts (nevermind in the lukewarm piping thereabouts) I'd appreciate a few pointers and apologize if I am rekindling a much discussed issue where everything has already been said. heatinghelp pointers to previous wall threads might indeed be as well informed and encompassing of current literature as any sources..

My inclination would be to view this the same way i view the sudden fascination with building level entry backflow preventers, i.e., as some combination of precautionary hysteria and rent seeking by manufacturers and plumbers. How ever did we survive this couple of centuries of piped water without such things? Suddenly, with no know recent outbreaks of water system borne disease related to back mixing of pathogens entering from end user location, we are suddenly faced with an industry requiring these devices.

If there is a risk in an apartment building of contamination and backflow, why wouldn't our water systems also require these devices be retrofitted on single family homes? The use is no different in an apartment building. My guess is because it is a policy designed to tax those who are perceived to accept it as a cost of doing business and who aren't perceived as a threat to the institutions imposing the requirements.

It seems relatively inexpensive to comply with the general rule for backflow preventers on stagnant appliations like boilers and they have long been required in all such applications, not just those applications conceived to be 'commercial' or able to 'afford' it. Meanwhile, the most gruesome junk we see in municipal water continues to come from the antique pipes in the street, not from the buildings being served. So I wouldn't want to be cavalier in the face of serious risk, but i also wouldn't want to see highly unlikely risks inviting high cost mitigation as 'insurance'.

hot_rod

I suspect the legal system drives some of the legionella hype. Should not be long until we see lawyers highway billboards offering to get you legionella compensation

That being said, more and more outbreaks are being identified.

Some quick numbers crunching would show maybe a million a day in lost revenue, plus settlements fees for legal action when a hotel like this Atlanta one has potential legionella issues.

I happened to be in Florida showing our anti legionella offering to engineering firms when this latest Atlanta incident occurred.

I noticed every other billboard along Florida interstates were attorneys offering to get you compensation for "something"


https://patch.com/georgia/atlanta/three-sickened-legionnaires-disease-atlanta-hotel

pecmsg

More and More cases are being found because more and more the patients are tested for it! Before it was considered the flue, bad cold or bacterial infection.

pecmsg

The legionella bacteria is in ALL public drinking supplies. Chlorine does not kill it. It grows rapidity between 70 and 110°F. That's what makes cooling towers such a prime breading ground.
Heating above 140°F KILLS the bacteria!

ChrisJ

> @pecmsg said:
> The legionella bacteria is in ALL public drinking supplies. Chlorine does not kill it. It grows rapidity between 70 and 110°F. That's what makes cooling towers such a prime breading ground.
> Heating above 140°F KILLS the bacteria!

Don't go using facts now...

hot_rod

Water features also. Possible that the latest Atlanta outbreak was due to a fountain outside?

archibald tuttle

> @pecmsg said:
> The legionella bacteria is in ALL public drinking supplies. Chlorine does not kill it. It grows rapidity between 70 and 110°F. That's what makes cooling towers such a prime breading ground.
> Heating above 140°F KILLS the bacteria!

That indeed may be true so it undercuts the question of whAt would the source be but it just brings up the obvious question. If it's in there and we've been turning out hot water heaters down since 1970 why don't we hear of people deathly ill all the time from taking a shower?

@pecmsg also pointed out that there probably have been some low grade infections that weren't being diagnosed but it seems if this were a vector of concern there would be craploads of such cases. And is low grade exposure necessarily bad. My first instinct is to think that it might tune the immune system. It just seems if we are feeding vast quantities of pathogens into a reproduction and distribution system and not having epidemic response that the virulence and or pathways for infection are overestimated, the fact that some exposures or breeding grounds seem to more commonly produce deadly results not only notwithstanding, but standing in contrast.

JUGHNE

GFarra, if you do add the mixing/tempering valve at the WH, please let us know if and how well the gravity recir system works after the install.
I have the gravity system myself but run the water at about 130, I know that is hot but just the two of here for the most part.
Our gravity return goes into the bottom of the tank. IF I added a mixing valve I would probably leave it there.

Question for all: I have installed temp valves in hospitals and nursing homes. If no hot water is used then the pumped return goes back out thru the HW piping, with only a little 140 added to the system which may temp control to 115 or so.
The tank temp is 140, temp supply is the 115.
Does this seem likely to prevent the legionella curse??
If after "cooking" at 140 in the tank could the legionella redevelop in the 115 piping??
The hospital has to develop a plan of correction...is this theory of mine sound??

hot_rod

Studies show you need about 1 hour of contact at consistent 140F thought the entire piping systems. Controls on Legio systems track the return from the recirc to assure the entire loop has been elevated.

Time depends on how much coating of slime or minerals inside the piping that could harbor the bacteria.

Some areas are promoting 160F for 15 minutes to lessen the time the building is in "kill" temperature mode.

I've not met anyone that has exact documented answers to legionella control, this seems to be a tried and true in countries that have been doing it.

With so many people traveling these days it is often hard to pinpoint the cause of outbreaks, sometimes.

I'd worry most about care facilities retirement facilities, hotels etc.

EBEBRATT-Ed

So my question is what about ac condensate pans, drains and coils? I guess we will have to ban air conditioning because I don't see an easy fix for that.

We could be blowing legionella all through the house

JUGHNE

Ed, the way I see it, AC condensate would be below 70 degrees.
The cooling towers which I assume are "swamp" type coolers would have warmer water blowing around.
IIRC, this was the initial Legonaires outbreak. 1976, parade in Philly?, fans started on cooling tower and misted the crowd of American Legionnaires attending a conference .
Mostly veterans who fell within the main risk factors....age.... smokers, (I know as one of many vets who smoked) etc were stricken.
Apparently it took a massive outbreak of this many people to finally come to the conclusion that this was unique.
Thus the name was given as "Legionaries Disease", again IIRC.

JUGHNE

Hot Rod, so for the hospital and nursing home, could you crank up the temp to 160, bypassing the temp valve and flush out all HW lines. This would have to be under supervised operation with all patients and staff aware. You could only run maybe 3-4 lav faucets full bore at a time.
Every month or what have you read about this cleansing procedure? This is new ground for most.

ChrisJ

> @EBEBRATT-Ed said:
> So my question is what about ac condensate pans, drains and coils? I guess we will have to ban air conditioning because I don't see an easy fix for that.
>
> We could be blowing legionella all through the house

So basically what you're telling us is you don't believe in Legionaries Disease.

That's how I take this response.

hot_rod

JUGHNE said:

Hot Rod, so for the hospital and nursing home, could you crank up the temp to 160, bypassing the temp valve and flush out all HW lines. This would have to be under supervised operation with all patients and staff aware. You could only run maybe 3-4 lav faucets full bore at a time.
Every month or what have you read about this cleansing procedure? This is new ground for most.

You would absolutely want a listen ASSE listed 1070 (point of use) valve at every faucet in the building when you elevate temperature, even @140F. Until those are in place I would probably not recommend elevated temperature option.

The 1070 valve is limited to 120F, although it can be adjusted lower. Most codes recommend 110F for some applications, day care, elderly facilities for example.

Chemicals are another accepted method, but they too have some "baggage"

archibald tuttle

ChrisJ said:

> @EBEBRATT-Ed said:

> So my question is what about ac condensate pans, drains and coils? I guess we will have to ban air conditioning because I don't see an easy fix for that.

>

> We could be blowing legionella all through the house



So basically what you're telling us is you don't believe in Legionaries Disease.



That's how I take this response.

@ChrisJ
that's not how i read what he said. although it's a different question whether moisture pulled from the air would gather legionella, maybe from deposition . . . and then in order for that to evaporate it is going to warm from the temp it was condensed at so maybe he has identified another vector.

I think what @EBEBRATT-Ed is implying is that thinking of every possible fertile ground for propogating and spreading legionella would give an almost infinite task. Given that this bacteria is ubiquitous and hard to kill (someone said chlorine doesn't do it either although there seem to be contrary indiciations, maybe its a concentration issue or retention of concentration through the system . . . ) and we all have no doubt experienced some exposure to it, where is it actually relevant to focus because resources are not unlimited.

I believe wikipedia suggests that 2 to 9% of non hospital pneumonia is caused by legionella. (I don't know the hospital based figure although it would seem that by its nature hospitals would house folks with who might be particularly at risk from more life threatening manifestation. still, should the effort be to prevent aerosol spread or to kill the bacteria in water pipes, or both . . . and maybe there is cost/benefit in that expense but the descriptions here of how to 'sanitize' hospital hot water systems are not cheap to institute).

And coupled with what appears to be the truism that legionella is most dangerous to those with compromised immune systems, it does seem that attention should focus on their settings and circumstances given the complications and expense of instituting industrywide controls. That might include home settings but I don't see a justification here for altering all homes. Just like most of us don't carry one of those personal alert devices until we expect to fall down and not be able to get up (although with the ubiquity of cellphones technology has given us a plausible alternative that is useful for others things, so if there is a low cost plausible solution for various of these vector circumstances it might become wise to desseminate it more thoroughly but i haven't heard one mentioned yet).

hot_rod

I feel for the average home where water is flowing every day, elevating the tank to 140F and adding a mixing valve set to 120F is an inexpensive and wise first step. That would kill any bacteria in the tank and pretty much eliminate it in the piping. Maybe once a month crank the mix valve to 140 and run all the HW taps for a few minutes. It is also good to exercise a mixing valve like that to help eliminate scaling of the cartridge.

Vacation homes or homes that do not use all the remote faucets often would be more concerning.

Code suggest 120F DHW temperature for homes, if you and the family are comfortable with 140F at the fixtures, just run the tank at that temperature.

Back in the day, most all tanks were set at 140F or higher, just saying

Yet another option run the tank hot and install point off use 1070 mixer at critical sinks. Most single handle shower valves have been scald guard for many years, so basically hand sinks, kitchen sink and two handle tub fillers, possibly.
I like the kitchen sink at 140F, the dishwasher works better, although many have a boost element, and hand washing at 140F rinse eliminates that bacteria concern.

The chlorine or chloramine percentage that public water providers add is not sufficient to kill the bacteria. I think the chemical anti legionella method is to super shock, then filter it back out before it flows thru the home or building.

I know a guy that used to treat many of the fountains and water features in San Francisco, he used fairly heavy duty chemicals and documents the dosage for liability protection.

JUGHNE

The hospital I speak of is 17 beds.
Often census is from 0 to 2 rooms occupied.
Occasionally full.

It seems when the census is 0 the DHW could be flushed at 160 degrees. The staff would have to be aware of this procedure with redundant warning signs in place.

The nursing home may have 25 residents. Most of whom cannot go to the RR unaccompanied. The same message to the staff and a close monitoring of mobile residents.

This seems a common sense method of the high temp flushing.
Any thoughts on this?

archibald tuttle

@hot_rod thanks for more comprehensive discussion. it certainly seems that the focus of chemical water treatment at the moment is public uses that have aerosol characteristics.

I'm trying to remember but I think the on demands i've bought recently come through set for 120 or 125 degrees. So there doesn't seem to be a widespread focus on higher temps in typical residential of small commercial settings.

Of course on demands don't house as much water but when not in use they would cool through the ideal temp zone albeit with much less volume. I would like to comprehend if there is really a public health hazard here beyond those with compromised immune systems - which is the focus of this work in hospitals with special concentration on transplant units where immune systems are deliberately suppressed.

I'm not necessarily an absolute believer in the literature from organized advocates on a subject, see my other responses to the 'consensus' on climate change, but I do want to understand what they are saying. Interestingly, this is the legionella.org response to ASHRAE guidelines that isn't particularly complimentary of the guidelines. While the process of creating the ASHRAE standard may have taken some criticism into account, the standard itself nonetheless relies on only two studies from 1980 and 1990 in indicting showering as a transmission modality and legionella.org cites 2002 meta study on hospital transmission that finds: "Many studies have explored the hypothesis that showering was a mode of transmission for hospital-acquired Legionnaires’ disease. Interestingly, most failed to link showering to Legionella infection."

It sure seems to me that the state of knowledge at this point is that we don't know and that sporadic legionella outside the realm of those with compromised immune systems is of limited, if not non-existant, concern. Significant professional focus has been on both prophylactic and acute treatment for health care settings and institutional settings where amplification in stored water settings justifies intervention in both water treatment and care in building ventilation design to prevent intake of possibly contaminated aersols.

Even when it comes to treating (or preventing) amplification - which ironically is really the area we are talking about but is not highlighted for action in the ASHRAE Standard - see diagram below, It does seem obvious that hotter temps are better but there remains disagreement whether there even is a standard for acute treatment and, for now it appears only emperical treatment and testing rather than standard routines can control. Once amplified residence in water systems is identified, these documents talk about as much as a half hour to each outlet at 160 degrees if biofilm or other confounding factors are present. We'll be having knock down drag outs between the anti-carbon and anti-legionella forces if anything like that were adopted as a regular widespread standard.

So it strikes me that the best technology we could possibly develop at this point are relatively inexpensive probes or sensors that can monitor the water system for this presence and reveal the efficacy of control efforts. Perhaps building design with the availability of on demand low temp exhaust units might, say, incorporate shorter home runs with a heater on each floor in a trunk designed like an elevator shaft to create a fire break to a machine/equipment room on each floor, and i believe that condensing on demands are designed to show the colder input water to the final exhaust such that condensing won't be lost altogether when delivering higher output temperatures. I might give that a short test and even just see what the upper limits of the technology are because i never even thought about it before.

Obviously of interest to techs would be the differing characteristics of copper and pex in possibly accumlating biofilm as well, as this appears to be a major player in amplification. What seems self evident while we don't seem to be able to establish an outright standard for treatment, is an action level (maybe i missed it in the ASHRAE standard), i.e. a threshold concentration at which amplification has become an issue, perhaps sliding scale depending on whether the setting is a hospital transplant ward, institution, home with vulnerable resident or just plain residence.

My sunday morning literature review must now be supplanted by lawn mower maintenance (i waited this long so i wouldn't be creating aerosols of dew). So that question along with others will await further study or enlightment from the assembled hoards.

ciao,

brian

hot_rod

ASHRAE 188 is more of a suggestion, not a standard really. I think NSF and two other associations are working on a more comprehensive standard which will indicate acceptable practices.

Much of Europe has a standard, I think Italy's has been in place for 10 years or more.

At Caleffi we developed a LegioMix valve for places where code requires elevated temperature. We have over 20,000 of these valves installed worldwide, about 10 years worth of service.

Basically a electronic mixing valves that can adjust to allow the high temperature flow at pre-determined times. The datalogger records the time and temperature to have a record for liability concerns. It also comes Modbus equipped for building automation tie in.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_22_na.pdf

GFarra

Wow, I left this topic thinking I had my answer and I raised the temp on my DHW heater. Using a meat thermometer I measured 145 degrees after running just the hot water at the kitchen sink and letting it fill a jug.

We use hot water on a daily basis. I am in the process of talking to a contractor on a new boiler and I'm starting to consider ditching my gas fired hot water heater and moving to an indirect setup off the new boiler. I will discuss the recirc line and mixing valve with my contractor as part of all of this.

Thanks everyone!

George

mikeg2015

I haven’t seen anyone mention that raising the water heater temp above 130, significantly increases mineral deposits on the heat exchanger surfaces. So it’s not just as simple as adding a mixing valve. Plus you lose some efficiency as well and on an indirect tank with a single stage boiler you may induce some short cycling of the boiler as well.

Just pointing out as few concerns I have.

Sometimes I’m concerned that our goal of a sterile environment creates some of hte issues we are trying to resolve. I enjoyed talking with a gentleman that built his home in 1950 on an open plot of land and for years, used cistern for his primary water supply. They grew up drinking contaminated water and it didn’t bother them. Jus a counterpoint. I’ve yet to encounter a mixing valve in the hundreds of homes I’ve been to in my area.

Seems like unless you have a compromised immune system, it might not be an issue since the bacteria is so common anyway.

ChrisJ

> @mikeg2015 said:
> I haven’t seen anyone mention that raising the water heater temp above 130, significantly increases mineral deposits on the heat exchanger surfaces. So it’s not just as simple as adding a mixing valve. Plus you lose some efficiency as well and on an indirect tank with a single stage boiler you may induce some short cycling of the boiler as well.
>
> Just pointing out as few concerns I have.
>
> Sometimes I’m concerned that our goal of a sterile environment creates some of hte issues we are trying to resolve. I enjoyed talking with a gentleman that built his home in 1950 on an open plot of land and for years, used cistern for his primary water supply. They grew up drinking contaminated water and it didn’t bother them. Jus a counterpoint. I’ve yet to encounter a mixing valve in the hundreds of homes I’ve been to in my area.
>
> Seems like unless you have a compromised immune system, it might not be an issue since the bacteria is so common anyway.

You do realize Rhinoviruses are super common too right?

mikeg2015

Yes, what’s your point? We are constantly surrounded by mold, bacteria, and viruses.

I just started as a service technician back in Jan. And I swear my nose runs less and I seem less sensitive to mold, dust etc. since I’m not constantly exposed to in almost on a daily basis.

I don’t think I’ll ever get used to cat or mouse pee however.

mattmia2

Swamp coolers and cooling towers are 2 different things.
Temps above 120 will kill legonella eventually but takes more time. Large recirculating systems seem to be more of an issue than single family systems.
Note that it will void the warranty on my HTP indirect if it is run over 140 f.

In commercial buildings it would make sense to recirculate dhw at 140+ and temper it at the fixtures.

I have considered running the water heater hotter and tempering the branch to the bathrooms while keeping the kitchen and laundry hotter. the hotter water can be helpful in dealing with grease on dishes, parts, and laundry.

mattmia2

The more I look at this the more I think the legonella issue in flint was only a result of the changing of the water source because the water had legoinella in it, the ultimate issue was improper design of their recirculation system.

archibald tuttle

@mikeg2015 color me a bit of a skeptic like you. I'm not recommending taking cynanide to get used to it, but certainly some potential, but ubiquitous, irritants or infectious agents are not within our capacity to eliminate and we should learn how to live with them. Legionella is tough because for some folks it is learning to die with them, but understanding the risks in relation to the solutions is important and I'm pretty sure we don't.

It still doesn't make sense to me if hot water delivery systems and recirc piping are a significant vector why we wouldn't have had ubiquitous earlier concerns. I have seen it suggested that there was a failure to previously identify legionella as the cause of any given pneumonia. That doesn't seem implausible but how big is that effect and by what surrogate is there any chance of characterizing that extent in the historic medical record. There still seems to be considerable lack of understanding of the actual mechanism of transmission and risk of infections in common household and non-institutional business environments, esp. relative to water supply systems vs. cooling uses. I am simply not clear how relevant or possible it is to eliminate legionella from water systems or the cost benefit of undertaking to do so.

I also thing the gold standard, as with boiler testing and monitoring, will be good field instruments for quickly characterizing amplification in any water system, esp. water system that serves compromised individuals or where the end use of the water provides established means of aerosol transmission.

pecmsg

archibald tuttle said:

@mikeg2015 color me a bit of a skeptic like you. I'm not recommending taking cynanide to get used to it, but certainly some potential, but ubiquitous, irritants or infectious agents are not within our capacity to eliminate and we should learn how to live with them. Legionella is tough because for some folks it is learning to die with them, but understanding the risks in relation to the solutions is important and I'm pretty sure we don't.

It still doesn't make sense to me if hot water delivery systems and recirc piping are a significant vector why we wouldn't have had ubiquitous earlier concerns. I have seen it suggested that there was a failure to previously identify legionella as the cause of any given pneumonia. That doesn't seem implausible but how big is that effect and by what surrogate is there any chance of characterizing that extent in the historic medical record. There still seems to be considerable lack of understanding of the actual mechanism of transmission and risk of infections in common household and non-institutional business environments, esp. relative to water supply systems vs. cooling uses. I am simply not clear how relevant or possible it is to eliminate legionella from water systems or the cost benefit of undertaking to do so.

I also thing the gold standard, as with boiler testing and monitoring, will be good field instruments for quickly characterizing amplification in any water system, esp. water system that serves compromised individuals or where the end use of the water provides established means of aerosol transmission.

There not a lack of understanding just the usual slow response to a relatively small issue until it popes up!

They've known of the problem but it is seasonal problem and a knee jerk reaction. The last outbreak in NYC was several years ago, response All cooling towers had to be registered, tested and certified. As far as I know it has ALL fallen by the wayside until the next outbreak! The registration was / is just another Tax!

ChrisJ

I had no idea we had this many microbiologists on Heating Help.
I'm impressed.

archibald tuttle

@pecmsg I get the cooling towers thing and that is aerosol almost by definition and then it is associated sometimes with circulation of air into the building. I'm talking about not knowing the significance of transmission through domestic hot water in showering and the like. The research i've seen doesn't bear that out as a source of infection, perhaps not even in the context of showering in hospitals. And this thread started on controlling legionella in DHW context. That is where I think we don't understand the risk as well from what i'm reading.

@ChrisJ not a microbiologist. just play one on the radio. but this thread has lead me to read various studies on this and i'm still up in the aerosol on the DHW side.

ChrisJ

archibald tuttle said:

@pecmsg I get the cooling towers thing and that is aersol almost by definition and then it is associated sometimes with circulation of air into the building. I'm talking about not know the significance of transmission through domestic hot water in showering and the like. The research i've seen doesn't bear that out, perhaps not even in the context of showering in hospitals. And this thread started on controlling legionella in DHW context. That is where I think we don't understand the risk as well from what i'm reading.

@ChrisJ not a microbiologist. just play one on the radio. but this thread hasa lead me to read various studies on this and i'm still up in the aerosol on the DHW side.

This is very similar, if not worse to homeowners doing plumbing and heating work. No?

mikeg2015

THere was an issue at a veterans home in Quincy, IL a few years ago. But again, here’s individuals with compromised immune system and a VERY large water supply network with 100+ year old piping and a recirc loop, that probably has dead legs in the piping an very low flow and turnover. A perfect breeding ground. They’ve made changes since.

pecmsg

archibald tuttle said:

@pecmsg I get the cooling towers thing and that is aerosol almost by definition and then it is associated sometimes with circulation of air into the building. I'm talking about not knowing the significance of transmission through domestic hot water in showering and the like. The research i've seen doesn't bear that out as a source of infection, perhaps not even in the context of showering in hospitals. And this thread started on controlling legionella in DHW context. That is where I think we don't understand the risk as well from what i'm reading.

@ChrisJ not a microbiologist. just play one on the radio. but this thread has lead me to read various studies on this and i'm still up in the aerosol on the DHW side.

A bit of a difference in a house with a 40 or 50 gal heater and a hospital with 2 ,3 ,4000 gals of hot water, Cooling towers and god know how many bugs flying around the air!