This is a space that seems that if people can get their water warm enough, they are generally happy. And the whole idea of "well, I haven't died yet" seems to be the rule for most folks - but it just doesn't sit right with me.
And if you use some eco means to "pre-heat" your water, followed by a hot water tank that will heat your water to 131 degrees, then you probably don't need to worry about this.
And this is a thorn in my foot that I just can't seem to get out. So I turn to all of you to help me get this thorn out ...
Apparently, this is something where a certain bacteria really likes really warm water. And if we shower with this same warm water and breathe in the mist from that hot water, we can get legionnaires' disease and possibly die.
Links from the old thread: http://www.osha.gov/dts/osta/otm/legionnaires/hotwater.html
Legionnaires' disease is a serious disease caused by Legionella bacteria, which thrive in stagnant, warm water. Outbreaks of this disease have been associated with cooling towers, evaporative condensers, showers, faucets, hot tubs/whirlpool spas, and other sources of aerosolized water. Legionella bacteria favor a temperature of 25-42 C (77-108 F) for growth.
. . .
People get Legionnaires' disease when they breathe in mist or vapor that has been contaminated with the bacteria.
[right][source: Centers for Disease Control and Prevention][/right]
Although some manufacturers set water heater thermostats at 140ºF, most households usually only require them set at 120ºF. Water heated at 140ºF also poses a safety hazard—scalding. However, if you have a dishwasher without a booster heater, it may require a water temperature within a range of 130ºF to 140ºF for optimum cleaning.
Reducing your water temperature to 120ºF also slows mineral buildup and corrosion in your water heater and pipes. This helps your water heater last longer and operate at its maximum efficiency.
[right][source: U.S. Department of Energy][/right]
So it sounds like all fresh water probably has some.
They are dormant at temps below 68 degrees (although, I suspect, other growies will probably thrive between 50 and 6.
They reproduce between 68 and 122.
If exposed to 131 degrees, they will die in five to six hours.
So, I suppose from 123 to 130 they are dormant.
The key is that a few of these aren't so bad. And if you simply drink them, then your innards kill them. The problem is when there are lots of them and you breathe them in - like in the shower.
In the city, the water is chlorinated. So the bacteria never get to your hot water system. And the hot water system is kept at 120 or higher - so if anything did manage to get in, it wouldn't get much of a chance to reproduce.
My concern is out in country. Well water or spring water.
The water goes into the solar hot water system or possibly a compost hot water system and then sits and warms.
If the system is used a lot, then the water might come out at 90 degrees - a really optimal temperature for the bacteria to reproduce. But it didn't get enough time to reproduce much, so all is well.
If the system is used infrequently and the temp gets up to 140 for a long time, then all the bacteria at the heat core are killed. Of course, there is a pipe coming in and pipes going out where the temp was not so hot. Those spots might now have lots of bacteria, but maybe it isn't so much. I want to call this "Problem Scenario B" and is focused on those bits of water just before or after the hot water.
If the system is used infrequently and temp does not go over 120, then it seems like this is a perfect breeding ground. I want to call this "Problem Scenario A".
I guess the first question is: how fast do they reproduce?
From the wikipedia article, the metric is "number of colony forming units (i.e., the aerobic count) of micro-organisms per mL at 30 °C (minimum 48 hours incubation)" (I'm not even going to try and make an acronym - although the table then lists "aerobic count".
10,000 or less is okay. 100,000 or more means take immediate action.
So .... maybe most water in colder regions contains something like 10. And the warmer regions is something more like 1000. So if you start with 100 and you have compost heated water, and you didn't use any water for a month and the pile drifted from 115 down to 95 during that month, then the conditions might be just right (speculative). And from what little I have read, if four people come home from being gone for a month, and one person takes a shower, everybody in the house - and possibly the neighborhood could get sick.
Further, even if somebody has a water heater to make sure the temp is 120 - they could still get sick since the first heater is loaded to the gills with bacteria and the second heater isn't hot enough to kill them.
So ... at this point I guess I have only the one question: how fast do these buggers reproduce?
Legionella bacteria itself can be inactivated by UV-C-Light. However, Legionella bacteria that grow and reproduce in amoebae or that are sheltered in corrosion particles cannot be killed by UV-light alone. An innovative way is the combination of ultrasonics' and UV-C-light. This uses a two stage process, where ultrasonic cavitation disrupts the amoebae or corrosion particles and leaves the Legionella bacteria exposed for UV radiation. Such combined system are used for example in hot water systems in sensitive areas, such as hospitals, where the inhabitants are more vulnerable than in normal environments.
Legionella will grow in water at temperatures from 20 to 50 °C (68 to 122 °F). However, the bacteria reproduce at the greatest rate in stagnant water at temperatures of 35 to 46 °C (95 to 115 °F).
Legionella longbeachae, an organism in the Legionella family, is found in soils and compost. Thus, the dust from purchased bags of soil, compost, or potting mix is also a potential source of Legionella.
In that case, here are some scenarios that could lead to death:
scenario 1) Solar hot water pre-heat and an electric hot water heater set at 120. Folks are gone for four cloudy days. The pre-heat stuff cycles up to as much as 120 and as low as 70. Spending a lot of time in the 95 to 115 range. Enough to accumulate 48 hours. The people come home and shower. It takes a full day to use the hot water that is in the electric hot water heater, which is slowly replaced with water from the solar source. Since a temp of 120 pushes the bacteria into a dormant state, the deadly bacteria are dormant when they are used throughout the day on the second day. It then takes about three more days for people to be sick enough to go to the hospital. At which point, by the time it is figured out what it is, one out of five are already dead.
scenario 2) Heat via compost pile. I have a video of an example of this. In that video they use 100 feet of 1/2 inch poly pipe. 1200 inches * pi * (0.25^2) -> 236 cubic inches. There are 231 cubic inches in a gallon. So the pipe holds about a gallon. Most shower heads are 3 gallons per minute. And an average shower is about five minutes. So only one gallon out of 15 contains our toxic bacteria. 15 times less than scenario 1. However, with the compost pile, if the temp is, say 105 degrees and it sits for a week, then it could have 50 times more bacteria. But this gets me thinking again: for the bacteria to multiply, surely it needs more than an optimal temp - it's gonna need food too. And plain ole water from a well or spring is probably really low on food. I suppose pond water could have a lot more food.
If the water has access to sun (like in a solar setup) then light can be converted to food. But in a compost pile it is dark. So that trick won't work.
Can anybody even validate my reasoning, even if we're missing some critical bits of information?
Amoeba (sometimes amœba or ameba, plural amoebae) is a genus of protozoan.<-Wikipedia
It seems that Legionella lives inside an ameba and probably has a parasitic relationship.
A protozoa is neither a plant nor an animal so I don't know if it needs direct light to get nourishment.
It looks like bacteria has also been given it's own kingdom now - so Legionella is neither plant nor animal and may not need direct light either. (When i was in school bacteria didn't have its own kingdom.)
Some microorganisms only reproduce under certain conditions but don't have to die without food and water...(some form spores and go into a stasis until conditions are right for them to thrive). <-like if they get inside YOU.
If there is a chance that yer water is contaminated, it wud be best to use pasteurization or reverse osmosis filtering for drinking water and chlorine for other water.
Micheal Reynolds has designed water filtering systems for just about any water... I think it is found in his Earthship books or website.
So, yeah, you could filter it. But, of course, it is easier to set something up without a filter. I guess rather than add layers of safety to everything, I would like to better understand what the problem is. Once understood, I might able to leave out the filter in the right conditions.
Wikipedia mentions "48 hours incubation" - so I'm thinking 48 hours is meaningful. As opposed to something like "60 days" or "10 minutes."
But .... to reproduce, it seems that incubation would require more than just the right temp. If legionella is introduced to two petri dishes, one with distilled water and the other with pond water, will their be a difference in reproduction? Would the distilled water sample have any growth?
I ask this because I think that legionella in a puddle of well water will probably nut budge, while legionella in pond water would probably go hog wild.
But I'm not sure. So I'm fishing for knowledge - in full realization that this is an area far beyond my ability.
Environmental Monitoring and Risk Prediction
The role of environmental monitoring in Legionella prevention has been the source of debate for many years.3 However, several studies exist that provide evidence for the use of monitoring in the prevention of hospital-acquired Legionnaires’ disease. Two studies from Spain show that Legionella colonization was extensive
(Cost-Effective, Practical, Evidence-Based)
(Costly, Impractical, Not Evidence-Based)
1. Quarterly Culturing of the Potable Water System of Transplant Units for Legionella Species (Spp.)*
2. Sterile Water for Rinsing Nasogastric Tubes and for Enteral Nutrition for Transplant Patients*
1. Any Legionella Spp. Detected, Decontaminate the Water Supply, Remove Aerators, Restrict Showering†
Care & Maintenance
1. Complete Eradication of Legionella Is Not Feasible and Regrowth May Occur After System Disinfection†
2. Disinfect Dormant Water Lines in Patient-Care Areas Prior to Being Returned to Service‡
3. Store Hot Water at 140°F (60°C)†
1. Routine Thermal Disinfection (At Least Semiannually) of the hot water system. Flush Each Outlet ≥5 Min. at 160°F (71°C) or ≥2 ppm Free Chlorine†
2. Remove, Clean, Disinfect Showerheads and Faucet Aerators
Monthly in Transplant Units†
3. Eliminate Dead End or Capped Pipes‡
Recommendations grading system used in an online medical resource at www.uptodate.com. *Consistent/reproducible evidence from controlled prospective studies. †Consistent/reproducible evidence from case studies. ‡Anecdotal reports that are not peer-reviewed.
It seems that living with Legionella is something that we must do. It looks like you cant get sick from drinking it, but you get sick from inhaling it from a water mist (like maybe in a shower).
The hospital, in the above article, raised the temp to 140 at the hot water heater and that stopped them in the water heater.
Even if you get water at the water heater to 140 F to prevent it there, the organism can grow in the lines or faucets - where the temp is lower... it looks like they had some luck raising the water temp in the heater to !49 F.
That is very close to pasteurization temp. And there are other microbes besides Legionella.
To prevent sickness it seems that pasteurization is the least you should do... Filtering can lessen some other things like farming, industrial and other wastes.
In a survival situation or emergency it would seem that you should not get the water out of the well until you are ready to use it.
You are right that pond water would be far more dangerous... if you ever get pond water under a microscope, you can see a whole world of things living in a drop.
Rain water might be safer than anything you could get in a well, but then it doesn't rain every day- so it seems that a solar still or solar pasteurizer is going to be something to have.
the tech is out there but its not the cheapest in the world. if you can get some sheet copper you can treat it with several acids and salts to make an infra black and build your hot water panels with copper tube make sure you cant stop the water flow cause in 1/2" tube the water will flash to steam. you need the system to have an up type flow so the steam will travel.
And i have not completely thought out yet how to build a solar/rocket hybrid,,,but i've been thinking of it.
Michael Reynolds claims 400F in his solar toilet... but i'm not sure how he got it that hot.?
# 70 to 80 °C (158 to 176 °F): Disinfection range
# At 66 °C (151 °F): Legionellae die within 2 minutes
# At 60 °C (140 °F): Legionellae die within 32 minutes
# At 55 °C (131 °F): Legionellae die within 5 to 6 hours
# Above 50 °C (122 °F): They can survive but do not multiply
But I guess the big thing is: how fast do they reproduce under optimal conditions?
About how many are there in well water?
Speculation: It would seem that if the water comes from a well and the water is kept in the dark, then growies are kinds dependent on what is aleady in the water for food. But if you add light, some stuff can convert that into food - which leads to food for the legionellae.
On the other hand, my impression is that the insides of pipes are just loaded with goo. Could it be organic in nature? In which case, there is ample food for legionellae and they just need the right temps.
So: what do they eat? How fast can they reproduce?
There is very very little chance of getting Legionella from raw water and less chance of getting sick from Legionella from well water...
Here's the EPA link : http://www.epa.gov/waterscience/criteria/humanhealth/microbial/legionella.pdf
Here a growth rate link for bacteria in general: http://www.cellsalive.com/ecoli.htm
Legionella can form capsules in adverse conditions and that is a stasis conditions to allow it to survive until conditions get better (kinda hybernate).
Legionellae are in nearly all water already.
It isn't a boolean thing: if you eat any you get sick. It's more like a tolerance thing. You can cope with a certain level. But when that level gets high enough, then you get sick.
As for the hospital: these are folks that are already having trouble fighting stuff off, so if you then add in a normal amount of legionellae, then they get sicker. But if you can get it down to zero, or way below normal, then it's better.
They did find that , people with health problems,had a better chance of getting sick with Legionella, but they also concluded that most of the population was immune to getting sick from legionella.
They also tell of ways to kill the bacteria, and they speak of many different ways that conditions are optimal for growth.
It would seem that there are other things in water that should concern you more.
If conditions are dry they form capsules (stasis/hybernation/ suspended animation or whatever it';s called these days) and can be like that for great periods of time.
I hate to go back and scan that whole document for the immune conclusion- when i read it i did a double check so i'm sure it said it...and if you think about it ... it makes sense... the organism seems to be all over the place so we are getting exposed to it often. Our immune system has this amazing ability to form antibodies to things that we are exposed to...
I count that 20 minutes happened 20 times. 400 minutes is 6 hours and 40 minutes.
So if we went from 1 to over a million in 6 hours and 40 minutes, then in another 6 hours and 40 minutes it would be a million times more than that. A trillion.
So it would seem it could become deadly in 12 hours.
That's quite a bit different from getting to a billion in a month. Can you help me figure out where my math is errant?
The reason why I want to find hard evidence of people being immune is that my reading suggests that nobody is immune. Rather, it's a matter of how people can cope with a small amount - our immune systems will clobber a small invasion. But if something goofy happens and we get a megadose (coming back from a week of vacation when it is cloudy) it's too much. People that are young or old or already sick, get clobbered worse/faster/easier.
The thing is that I wanna really get my head wrapped around the particulars. The exact data. I've done a lot of reading now, and I feel like these two questions are still pretty open.
The EPA assertion may not be accurate as Medicine.net says that they dont know how many people get the disease and show little or no symptoms..
They kinda go into prevention but i dont see anything much except the tail chasing the donkey, as they diagnose the disease then go looking for the cause.
They mention stagnant water and water mists and cooling towers as likely sources.
If you expect exact math it is $200.00 per hour.
If you expect exact math it is $200.00 per hour.
I'll trade you $200 per hour for exact math for $200 per hour of using my forums!
(just kidding dude! You are not the first person I've tortured with my math needs.)
Your new information seems aligned with the information I've been reading.
Stagnant water does seem to be the key. One thing I read was that one of the best places to find it was fountains that have underwater lights. The lights heat the water and the fountain gets that water into the air.
I wonder about stagnant water + sun. It would seem that if you have a pond that gets no sunlight, the water will probably be clear. But if you do get sun, you will get lots of algae. With lots of algae, there will be lots of critters. Like amoebas. Which can harbor more legionellae.
I'm gonna speculate that the optimal temp for legionellae is 105 degrees F.
So, well water in a 1/2 inch poly pipe in a compost heap at 105 .... there is no light. And the temp can hold very steady. After a day, or a week, what is the status? I'm gonna guess that there is something near zero food in the water, so there is gonna be something near zero legionellae. But what about scummy stuff inside the pipe?
solar hot water with a week of clouds is another story. That gets sunlight. So food can be made. And there is still goop in the pipes that might be food.
Anybody have any idea what the goop in pipes is made of?
It may depend on the color or other characteristics... most likely wud have to be cultured and tested to tell exact organism.
It seems that bacteria or algae are suspect culprits.
A friend gathered a lot of info that is helping me to get my head wrapped around the two questions. And he did provide something that seems to bring a little focus to the first question, although it would be great to get a more definitive answer for the first question:
"Over a 4-day period, L. pneumophila grew more than 100-fold in the presence of D. discoideum (Fig. 1). The rate of growth between days 1 and 2 was rapid, with a doubling time of approximately 6 h, but slowed on days 2 to 4 post infection to a doubling time of approximately 16 h. "
So the answer as to what do they "eat" is that it is dependent on what it is that the organism is on.
They dont have to eat to exist...they can just wait until conditions are ideal then divide. Kinda like a seed can sit without eating... it just waits until conditions are right - then undergoes cellular division. (Bacteria will die under adverse conditions - some land on metal and die - some are killed by soap - most are killed by antibiotics.)
The CDC seems to agree with the EPA report...Most people will not have any symptoms when contacting Legionella .
Center for Disease Control site/links about Legionella bacteria:
What should I do if I think I was exposed to Legionella bacteria?
Most people exposed to the bacteria do not become ill. If you have reason to believe you were exposed to the bacteria, talk to your doctor or local health department. Be sure to mention if you have traveled in the last two weeks.
A person diagnosed with Legionnaires' disease in the workplace is not a threat to others who share office space or other areas with him or her. However, if you believe that there your workplace was the source of the person's illness, contact your local health department.
Site to get CDC info on Legionella:
CDC site to get Ways to decrease Legionella:
5. Maintenance Procedures Used to Decrease Survival and Multiplications
of Legionella spp. in Potable-Water Distribution Systems
Wherever allowable by state code, provide water at >124°F (>51°C) at all points in the heated water
system, including the taps. This requires that water in calorifiers (e.g., water heaters) be maintained at
>140°F (>60°C). In the United Kingdom, where maintenance of water temperatures at >122°F (>50°C)
in hospitals has been mandated, installation of blending or mixing valves at or near taps to reduce the
water temperature to <109.4°F (<63°C) has been recommended in certain settings to reduce the risk for
scald injury to patients, visitors, and health care workers.726 However, Legionella spp. can multiply
even in short segments of pipe containing water at this temperature. Increasing the flow rate from the
hot-water-circulation system may help lessen the likelihood of water stagnation and cooling.
Insulation of plumbing to ensure delivery of cold (<68°F [<20°C]) water to water heaters (and to coldwater
outlets) may diminish the opportunity for bacterial multiplication. Both dead legs and capped
spurs within the plumbing system provide areas of stagnation and cooling to <122°F (<50°C) regardless
of the circulating water temperature; these segments may need to be removed to prevent colonization.
Rubber fittings within plumbing systems have been associated with persistent colonization, and
replacement of these fittings may be required for Legionella spp. eradication.
Continuous chlorination to maintain concentrations of free residual chlorine at 1–2 mg/L (1–2 ppm) at
the tap is an alternative option for treatment. This requires the placement of flow-adjusted, continuous
injectors of chlorine throughout the water distribution system. Adverse effects of continuous
chlorination can include accelerated corrosion of plumbing (resulting in system leaks) and production of
potentially carcinogenic trihalomethanes. However, when levels of free residual chlorine are below 3
mg/L (3 ppm), trihalomethane levels are kept below the maximum safety level recommended by the
In my system the tank water doesn't even circulate. It just sits in the tank and the panels have their own heat exchanger in the tank so the panels can have anitfreeze in them to protect against freezing. In this way, neither the water from the panels or the water we use ever contacts the water in the storage tank and the water we use never comes in contact with the water from the panels. We have a drilled well a few hundred feet deep that supplies the water we use each day.
Our system was built a long time ago and works really well but newer ones take an extra precaution and the heat exchangers are double walled and required to be by so by code.
Even with all these precautions I suppose there's always a chance one could get sick but I don't believe there's any more chance of it using a conventional system than a solar system. The key is to eat as well as you can and be as healthy as you can so you can fight off disease whenever you come in contact with it no matter what it is. for those with compromised immune systems there are home water purification systems available now that seem to do a really good job as an extra layer of insurance if needed. They are still pretty expensive though.
A properly built solar hot water system ...
I think there are two important points here.
1) Many people consider their solar system to be "properly built" even if it is a style that is an awesome legionella incubator.
2) I think that the style of the heat exchanger where the solar stuff doesn't touch the shower water is, IMOO, a step in the right direction, and not entirely safe from problems. And the idea of "fresh" is a big key here. The danger scenario is one where folks have been out of town for a week and then take a shower.
At a solar hot water demonstration workshop, the guy leading the workshop had apparently installed lots and lots of solar hot water heaters. Some in the city where the codes require the heat exchanger and some in the country where that wasn't a requirement. He expressed that the city codes were built from ignorance and are mostly about "the man" showing off that he can make you jump through hoops. When I asked about legionella, my impression was that he had never heard of it and I was quickly shamed into droping the topic.
Once we get this all figured out, I think it is important to spread the knowledge in a short and easy to understand way. Then there would be a path for all systems to be used safely.
After all - so far it seems like if the hot water came from a cold source less than 12 hours ago, it is probably 100% safe.
I have been running a solar water heating innovation company in UK for a decade. Having started my career as an aquatic biologist, I have been looking at Legionella in depth. One issue is solar hot water storage, and I hope this post is interesting to an international audience.
In UK, the solar water heating industry is not actually complying with government safety guidance on Legionella and a major shakeup of the solar heating industry is happening right now.
Technically, this guidance (UK HSE Legionella code and guidance L8 para 15, contains a "pack of four", which is:
1 Heat stored water to 60C (140F)
2 Heat it daily
3 Hold it at 60C for 1 hr
4 Heat the whole calorifier contents, including to the base.
Looking at point 4: the "whole contents to the base" requirement, it seems that many in the UK solar thermal industry may be noncompliant because of today's practice of heating part-way down the cylinder only.
From an insurance perspective, the majority of non-domestic solar thermal installations (plus certain domestic ones, such as those in rented and social homes - where L8 applies) may be regarded as noncompliant, and therefore as defective. The fact is that clients are normally within their rights to require all defects (ie faults) to be fixed - free of charge. But this could cost installers £200-£600 ($300-$900) per job. This potential liability (on top of the health and safety one to the user) worries of some major players in the industry and has caused some of them to be overtly hostile to a minority who seek to discuss this issue openly.
My having queried the para 158 noncompliance, and as part of a UK industry group meeting on the subject, the author of L8, Dr Tom Makin (full contact details and references are also available), wrote a report (you will find it on the UK Water Regulations and Advisory Service (WRAS) website) describing conventional solar thermal installations as being "highly likely" to be "creating a risk".
We were not included in this meeting, despite having been given assurances that we would be - and the report was kept secret. However we eventually obtained a copy of this report (under Freedom of Information law). Following our disclosure of this report on our website (as one is permitted to do) some months later it was published on the WRAS website.
I understand that outside Europe there have been cases of Legionella linked to solar thermal. As a company director I am obliged by law to comply with guidance - unless I can explain clearly why I should not. L8 is not a forgotten document: it is regularly used in prosecutions.
Recent evidence of successful L8 proescutions or censure of UK government agencies:
£24,000 ($36,000) fine plus costs: Welsh care home for inadequate legionella assessments http://www.hse.gov.uk/press/2009/coiw37209.htm
£25,000 ($37,000) fine plus costs: butchers / meat packers. http://www.hse.gov.uk/PRESS/2009/coinw01109.htm
£300,000 fine ($450,000) plus costs: Cider maker HP Bulmer Limited http://www.hse.gov.uk/PRESS/2008/wm421708.htm
£48,000 fine ($72,000) plus costs: Liverpool hospital. Unsafe levels of legionella in water for showers, etc. http://www.hse.gov.uk/PRESS/2009/coinw036trust09.htm
Even the prison service has infected prisoners http://www.hse.gov.uk/Prosecutions/documents/crowncensures.htm
There is more detail on the solartwin.com website.
I hope this is interesting. I can send readers papers if they want.
I understand that outside Europe there have been cases of Legionella linked to solar thermal.
And finally - a connection! So my concerns are valid.
I hope this is interesting.
I don't suppose you can tell me more about how quickly legionella reproduce, or what sort of food may or may not be available in solar water vs. a water tank. (my guess is that warm water in utter darkness is gonna be 100 times safer than warm water that lets light in).
On your interesting questions about Legionella nutrition and growth rates, plenty of useful work been published. In summary, they most like dirt and warmth. Being bacteria, rather than algae, they do not grow directly in response do light as plants such as algae do. Instead they feed on carbon-based biological material. That is why we only use silicone (ie non-carbon) rubbers in the Solartwin solar panels, in order to starve them. The following (free) guidance documents look at the above issues in detail, plus others such as ecology, biolfilm, and risk assessments.
- UK Legionella guidance (see para 15 is here: http://www.hse.gov.uk/pubns/priced/l8.pdf
- European Legionella guidance is here: http://www.ewgli.org/data/european_guidelines/european_guidelines_jan05.pdf
- World guidance is here: http://www.who.int/water_sanitation_health/emerging/legionella.pdf
There is also a youtube video on solar thermal and heating water stores to the base here: http://www.youtube.com/watch?v=J9v68zr213A
To simplify the solar plumbing appproaches into three:
1/ Dedicated solar preheat volume which may never reach 140F in winter. This is a major historical solar plumbing approach which is described in Europe as "industry accepted", "proven", "successful", "established" and "not a problem in low risk cases". However it may fail to protect people even in normal circumstances such as when:
- The backup heater is not running at the time when people take a shower. (Legionella is an inhaled pathogen.)
- The backup heater is running but high flow rate, or high water volume use mean that the water spends less than 1 hr passing through the backup heating zone. This could easily happen when people take showers consuming a volume which is greater than the hot top of the cylinder.
- The sun comes out nice and bright in the morning. A solar heat exchanger at the base of a cylinder may start at 20C, but soon heat small volume of water around it to say 70C. If the hot top is at 60C, the heat exchanger hot water at 70C will rise and destratify the whole cylinder. On a sunny morning you may end up with water at a temperature which is below 50C coming out of your shower.
The Dr Makin paper on solar thermal and hot water conditions for legionella appears to rate L8 noncompliant installations such as these as being "highly likely" to be creating a risk. References:
Dr Makin report: http://www.wras.co.uk/PDF_Files/Preheated_Water_Report.pdf
Some comments on it: http://www.solartwin.com/censorship-news-massive-solar-legionella-cover-up-revealed-today-by-freedom-of-information-inquiry
2/ Dedicated solar volume in time. This heats to the base, daily to 60C and holds it there for an hour in the evening. This complies with L8 and is safer than 1/.
3/ Thermal stores. Here the volumes and residence times are reduced dramatically with a corresponding dramatic improvement in risk assessment and is again safer than 1/.
Parts of the UK's and Europe's solar industry has adopted a seemingly unbalanced position in that 1 is promoted, while 2 is downplayed and 3 is completely omitted. The current approach incurs avoidable risks. Its prescriptive approach risks marginalising other potentially better approaches. A preferable, low risk, position might be that 2 and 3 are promoted as preferable to 1/, which would be phased out, over an agreed timescale.
So, what is happening elsewhere? Readers, do please let me know if this is useful.
Regards from Barry Johnston.
I guess the root of my comments is the idea of somebody that has a solar shower set up for interns where the water goes into the collector and then out the shower. Vs somebody who has a compost heap set up to heat water for interns. My thinking is that if the water is exposed to light, then pond life can build up which acts as a great spot for legionella to reproduce. Less light means less build up.
If we wanna talk about off grid, freaky-cheap solutions ... It seems that if somebody is gonna expose some sort of tank to the sun, it seems that the black stuff is better than the clear stuff so that you don't build up any pond scum which could feed the legionella (indirectly).
A better solution would be having a tank full of nasty hot water and a coil of fresh water that passes through the tank as an exchanger. This way, only the first 30 seconds of a five minute shower might contain more legionella. And if done right, that might even be able to be cut to ten seconds, thus vastly reducing the overall exposure.
The next step, I think, is to come up with some general rules of thumb for safety. With an optimal doubling time of six hours. A rough guess would be that under perfect conditions, a danger zone could arrive in three days. One could post a sign near showers that said "if this shower hasn't been used for three days, there is a risk of legionnaire's disease" followed by details.
Keep the shower pipes dry until just before using..
Heat a gallon of fresh filtered water in a simple solar oven to around 190 degrees then just before use dilute with a gallon of cool water and dump into the the shower.
Please do discuss / dispute my conclusion. We need debate because the green energy industry needs to grow up - in the right direction.
I hope this helps in the Legionella safety debate. Best wishes from Barry.
Crazy question: why not just heat water on the stove and sponge bathe?
While I can't speak for others, I can say that my daughters, darlings though they are, don't appreciate coming downstairs in the morning to see their dad naked in the kitchen touching himself.
Strange, I know, but what can you do? Kids nowadays...
brice Moss wrote:
seeing this post makes me wonder if someone is creating an issue out of nothing cause my 'lectric water heater thingy has a sticker on the door by the temp controll advising me not to turn it up over 130 which I ignored of course cause I likes it at 195 cause I likes to be able to make tea outa the kitchen tap when I'm in a hurry
AAAHHHH! NO! DO NOT DO THAT!
If your water has the least amount of minerals in it, your water heater becomes a cauldron of chemical reactions, esp. at the higher temperatures. Do a search on the web for do-it-yourself or home handyman videos of purging your water heater, and look at what comes out of some of those things, esp. the ones that are only 3 years old. Trust me, you'll switch to using the microwave to heat up your water.
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