Your domestic lines do not site there in optimal breeding temperatures as much, they do not have as much surface area, and they see much more flushing in most cases (especially in those shoulder seasons). It's really not that confusing.

You most likely DO have legionella in the domestic.. most people do. Just not in concentrations that are dangerous to healthy people. That can be changed by giving them 1000 feet of home though. You can close off the high-concentration homeland for them, and make them try and eke a living out in your water heater and a lot less domestic line. Maybe that still won't take down a "healthy person", but it surely has to change the definition of what is "healthy enough" to repel the little buggers.

You have to make your own choices. Thats all. There is a pile of information that is available to think about.

Exactly why I love this site.
 
This thread started with the professional advice that said an open system could result in
Legionaires and now those same professionals have to admit that a closed system could have Legionaires as well.

My system, my choice as long as I have all the facts.

The funny thing is you can do the research. There is no reported cases of Legionaires caused by open systems. There is however recorded cases of Legionaires in domestic systems.

You are far more likely to catch it when living in large structures such as hotels, arpartment buildings and hospitals where the domestic water system is large and complicated.

Here is a good link.
http://www.mayoclinic.com/health/legionnaires-disease/DS00853/DSECTION=causes

Here you go,
read this, http://www.hcinfo.com/ldfaq.htm
A couple of points;
Q. Is Legionnaires disease common?

A. Legionnaires’ is not rare. It is perceived as rare only because most cases are never detected, and not all detected cases are reported to public health authorities. Because underdiagnosis and under-reporting make incidence of the disease difficult to estimate, figures have varied widely. The (U.S.) Centers for Disease Control and Prevention (CDC), Atlanta, has estimated that the disease infects 10,000 to 15,000 persons annually in the United States, but others have estimated as many as 100,000 annual U.S. cases.

Another reason that Legionnaires’ is falsely perceived as rare is that when cases are detected, the public rarely hears about them. Most cases—at least 65 to 80 percent in the United States and the United Kingdom —occur sporadically (one or two at a time). Thus, only a small percentage of cases occur as part of the multicase outbreaks that sometimes make the news. Cases of the disease are seldom publicized even when lawsuits are involved, because most Legionnaires’ lawsuits are settled quickly and under terms of confidentiality.

There is more!!!

Q. Are certain types of buildings more prone than others to have problems with legionellae?

A. Cases of Legionnaires' disease have been linked to many types of equipment that contain water, but plumbing systems and air conditioning systems are most often blamed. Although it is possible to contract the illness from legionellae growing in home plumbing systems, most cases have been traced to large buildings. This may be because larger piping networks are generally more conducive to legionellae growth. Also, the air conditioning systems for large buildings often include cooling towers, which contain a pool of warm water in which legionellae can flourish.

So I am highlighting just a couple points from the article, it is worth the read, notice however that a large number of cases are suspect of not being reported upwards of 100,000. Also notice that preventive steps include minimizing the Hot Water Plumbing pipes in a system. With in floor heat often on a 2,500 sq ft home 4,000 feet of heating pipe can be placed. You might find this is not to far from the amount of hot water plumbing pipes in a 25,000+ sq ft commercial building. The little home just joined the league of a commercial building in relation to domestic Hot Water Plumbing pipes.

The real argument may be support for converting all domestic H20 systems to flash type water heaters and overheating then tempering down delivered hot water.

Dan

Seriously, you're being pretty selective in your understanding here. Most domestic systems have some legionella in it, yes, that does not make a typical domestic system equivalent in any way to an open freshwater heating system, no matter how much you choose to ignore the arguments to the contrary. Dan here pretty much summed it up,, add a heating system and your piping system is suddenly a lot like a much larger institution's plumbing system.

though any domestic system could be run at high temps with point of use scald valves, I wouldn't give up on tanks..

Explain how I am being selective.

I know the facts, all the facts! My piping may be longer but I take precautions just as I would with a closed domestic system.

As I have said before I bet my whole open system is far better protected that most closed domestic systems.

You keep acting like a closed domestic system is an equal or even comparable risk. In a domestic home setting, in most cases, that isn't even remotely true. That never used guest shower, maybe, but given how rarely it would see prime growing temperature, probably not. Adding thousands of feet of pipe to a domestic system is in no way equivalent to a standard domestic system. You might manage your risk, but that does not make the two situations comparable. Adding a heat exchanger doesn't mean that no one can or will ever get legionella, but it does remove a significant potential for growth... amongst the other protective benefits to the heating system, and your house.

Talking about diagnosed cases from open systems is, frankly, ridiculous. Hydronic systems of any kind are a very small segment of american heating systems: Radiant, far less so... freshwater radiant, infinitesimal. I would be stunned if anyone HAD a diagnosed case that was actually pinned on an open system (how often are individual cases really traced to the source, nevermind the ones that are never diagnosed or mis-diagnosed?), and even if they did, I'd be even more stunned if anyone else ever heard about it.

You can be as actively involved with your risk management as you like: but please don't muddy the issue with irrelevant or misleading arguments. You multiply your bacterial homeland by 10x or more in most full radiant systems, that has to increase risk, and the fact that we don't have a pile of bodies to point to doesn't really mean a thing. It took fifty years for the tobacco lobby to lose on lung cancer, how easy do you think this would be? This is positively obscure.

Actually if you do the research you will learn that doctors are suppose to test pneumonia cases for the Legionaires. Proven cases then are then supposed to be investigated for the cause. This is because most cases of Leoginaires stem from institutional sources and are a public health issue.

I have not muddied the issue in the least. I have provided information and the other side of the story. I have not avocated for any postion. I shared information.

and yet the CDC estimates that most cases are never diagnosed, or are mis-diagnosed. how to reconcile that with what is apparently "supposed" to happen?

Your last posts clearly pointed to some equivalency argument that quite simply isn't true.

This thread started with the professional advice that said an open system could result in
Legionaires and now those same professionals have to admit that a closed system could have Legionaires as well. Ring a bell? This statement serves only to act like somehow the presence of legionella in regular domestic systems has anything to do with what we are discussing regarding freshwater heating systems. That's an attempt at a "damned if you do, damned if you don't" argument.

The two scenarios are not similar, and that is an irresponsible statement. Ditto for the attempt to back it up with the diagnosed case statement, which anyone who has done a passing amount of research on this topic should immediately see is really quite far into left field, frankly.

"This thread started with the professional advice that said an open system could result in
Legionaires and now those same professionals have to admit that a closed system could have Legionaires as well. Ring a bell? This statement serves only to act like somehow the presence of legionella in regular domestic systems has anything to do with what we are discussing regarding freshwater heating systems. That's an attempt at a "damned if you do, damned if you don't" argument."

Actually I don't see it as a dammed if you do argument, it is an example that we live with it every day whether we have an open or closed system. It is telling both sides of the story not escalating one or the other.

Why do you seem so upset that I share information about this? I do not claim to be any sort of authority? do you?

At least this converstaion will help people to know that they should do the research for themselves and not always believe that someone selling a product has all the information, just as they should know that I don't either.

Man,
did you read the post I placed for your eyes jmagill, I will place it again;

A. Legionnaires’ is not rare. It is perceived as rare only because most cases are never detected, and not all detected cases are reported to public health authorities. Because underdiagnosis and under-reporting make incidence of the disease difficult to estimate, figures have varied widely. The (U.S.) Centers for Disease Control and Prevention (CDC), Atlanta, has estimated that the disease infects 10,000 to 15,000 persons annually in the United States, but others have estimated as many as 100,000 annual U.S. cases.

Another reason that Legionnaires’ is falsely perceived as rare is that when cases are detected, the public rarely hears about them. Most cases—at least 65 to 80 percent in the United States and the United Kingdom —occur sporadically (one or two at a time). Thus, only a small percentage of cases occur as part of the multicase outbreaks that sometimes make the news. Cases of the disease are seldom publicized even when lawsuits are involved, because most Legionnaires’ lawsuits are settled quickly and under terms of confidentiality.

This was only a portion of the answer,
Open loops are heat on the cheep.
Rob is right with the fact that statistically the radiant systems in the USA are about 5% of all residential systems. Now what portion of that s open loop? Who is monitoring that 3-5% maybe window of open loop systems across this great land? Oh I remember it is our health care providers because they care and have a lot of time to run expensive tests on Joe Shmoe's body fluids. There is a problem because in fact you are hearing about it, right here, by people that have been observing the right way from the wrong way. By CDC studies that confirm and or suspect untold cases due to mis diagnosis, Legal manipulation, and a host of other reasons. Open loop places huge amount of pipe in harms way to harbor the bacteria that otherwise would not have access to your shower water.
Its real.
Dan

Yet, it is allowed by building codes as stated in other posts.

I've said my what , I came to say. There is more than enough information here for people to see that there are two sides to this discussion. I have no further need to play volleyball with you. It will not change the facts.

And interested parties lobbied to make it accepted in building codes, as well. More people "selling a product". so what? "Code Minimum" has rarely been a particularly compelling reason to do anything. Obviously no one has spent the large dollar required to research this scientifically for such a small portion of the building industry and so any codes on the matter are going to reflect this lack of scientific rigor on the matter.

Share info all you like, there is plenty of room for reasonable disagreement, the back and forth is fine and, if I say so, is creating a fun and informative debate: but that particular argument was not fine. That was a cheap shot and way off the mark. And now trying to portray it as simply "sharing information" is disingenuous at best. It's not "telling both sides" to say we live with legionella every day: that side was already told. We all live with legionella in safe concentrations every day: that's the important part... safe concentrations. When it escalates into UNSAFE concentrations, as in institutional plumbing/AC systems, rarely used fixtures above regular room temp especially, or perhaps freshwater heating systems, then there is a problem.

Given I started this thread... let me add my 2 cents.

First of all I wanted to thank everyone for participation and knowledge sharing.

Now back to the topic: in reality nobody can quantify how much the open-loop system increases the odds of getting a Legionnaires. All I saw was a pure speculation - and I agree it is increasing the chances... maybe by 0.01% or maybe by 10X... once again - nobody knows.

I believe open system with recirculation timer that prevents the stale water is 100% fine. The only advantage of open system is price. The cons is maintenance and unquantifiable risk of Legionnaires. The average price difference comes at about $1,000 - includes basic valves, expansion tank, heat exchanger and pump. There are lots of plug-in kits that are being sold to easily convert open loop to a closed loop.

If all boils down to one question: would you rather... spend extra $1,000 on closed system that is a X% safer and Y% easier to maintain. I think each of us will have to plug in the "X" and "Y" and make an educated choice.

$1000 could be about half that on moderate and small systems, and again recirc doesn't stop the issue. You miss flood risks as a possible issue as well (ever seen a picture of a freeze up after an open system kept pumping water through a breach? not pretty). and it's not about ease of maintenance. Either the system gums up or it does not.

You're on the right track, really, but the "insurance policy" framing of the issue really sums it up better. Rare, but catastrophic problems can occur with open systems that do not occur with closed systems. It's not really incremental X or Y: it's a roll of the dice, and you get lucky or you don't. You'll probably get lucky. but if you don't...

Sounds like the wind is calming down here, we are getting blasted today on the west coast. ok as to cost have a look at the TACO x block, we sell em so do others, there about $995. Remember this is a strap on to any water heater with capacity. You get a lot of bang for the buck, out door modulation, 2 bronze pumps, a clean presentation, there capacity is about 50K BTU. not bad. or you can build your own what you would need additional is a bronze pump, and heat exchanger plus fittings.
Ether way there are better choices than open,
just my opinion
Dan

I read about some folks who bought a home in a co-housing community recently, their home brand new home had an open loop installed in a concrete slab application.  The home also happened to have polished concrete floors.  A contractor sealed the concrete to prevent staining, and a short time later there water became poisonous as the chemicals from the sealant leached into the PEX tubing.

I guess the whole thing turned on the fact they had to use PEX w/o an oxygen barrier because of the open system?

Probably beating a dead horse here....

I don't think oxygen barrier tubing would have helped. This would have been a problem with a PEX plumbing system as well, to be fair, if the plumbing were run in the slab as it often is in slab on grade homes. However, a closed system would certainly have reduced exposure, and without pex plumbing in the slab it would not have had any exposure at all if the system were closed.

sounds like a push, I do not support open systems but at the same time do not see how a sealer would travel thru a couple inches of concrete and then leach thru pipe and continue to contaminate the system??? perhaps there is a different source for the toxins. If they wait long enough there open loop system may give it own special poison.... But from the sealer, interesting. I would not want to be on the legal end defending myself from that.
Close the system.
Dan

in the situation I am aware of in washington state, the chemical that leached through the concrete was a neurotoxin that is present in the acid stain used on the concrete. one of the "-zenes".. benzene, maybe? I forget now. It wasn't pretty though.

the acid stain does leach into the concrete: and this contaminated the water.