Tempering tank for hot water system

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the old heater sounds like a ideal growing medium:(
Q. What water conditions are best for growth of the organism?
A. Warm, stagnant water provides ideal conditions for growth. At temperatures between 20�C-50�C (68�-122�F) the organism can multiply. Temperatures of 32�C-40�C (90�-105�F) are ideal for growth. Rust (iron), scale, and the presence of other microorganisms can also promote the growth of LDB.
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I'm wondering if the key word there might be "stagnant?" I don't know how long water would have to be stagnant for????? Days? A week? A few hours? I would think in a one family house that water would be moving through the hot water system at least daily. Do you think you would get anywhere close to 100% turnover in a hot water tank at least every couple days depending on usage? In my tanks (tempering tank included) the cold water inlet has a pipe extending down into the tank nearly to the bottom so the cold water entering must rise upward to exit the tank in the hot water outlet.
I just finished piping up my tempering tank yesterday evening. I figured it would take at least overnight or longer to see a change as our cold water is probably 50 degrees F and it took 52+ gallons to fill. This morning when running hot water for the clothes washer, the copper pipe with the tempered water going to the new water heater was just cool to the touch (guessing about 80 degrees F water). The pipe with the cold water that was entering the tempering tank felt icy cold. I took a reading on our electrical service meter this morning so I will be checking it for the next week or so.
Steve
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Another update: Looks like it just might be a winner.... After taking a couple more days of meter readings with normal hot water usage and other electrical usages remaining fairly constant, I figure we are using about 7 - 8 kwhs less per day. Tempered water going to the new water heater is fairly close to 100 degrees F. I think having the tempering tank near the wood stove with a recirc loop actually piped over the wood stove makes the difference. I'm considering one more piping change to the recirc loop which might capture even more heat from the wood stove....
Happy New Year! Steve
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On Fri, 26 Dec 2008 06:17:30 -0800 (PST), ransley

Look here for updates on recent outbreaks of Legionnaire's Disease, and you'll see several hotels listed: http://www.hcinfo.com/outbreaks-news.htm
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OK an interesting point it was in the hot and Cold water of a hospital, no hospital will heat under the 120f code, for a hospital code is probably much higher, but explain the cold water contamination and the fact they heat water very hot.
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cold water in such a large building may get warm easy, people are immune supressed, hospitals have labrinth of pipes, some water sources may get litte use with long sit times for cold water to get warm
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I see them listed, but no details for some of them. The original Legionnaires disease was from a Philadelphia hotel and it was the cooling tower that was infected, not the water system.
One case mentioned in your list had it in both hot and cold water so the temperature did not matter in that case. Another was a hot tub. Another was a fountain. Seems to be may potential sources but cooling towers are one of the biggest. From what I've seen, there is no sure way to eliminate it, but much potential to cause spreading.
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A few wraps of soft copper around the bottom of the exhaust stack pipe would pick up a lot more heat. Or, a loop around the stove, or a coil right on top[ of the stove. Of course, the copper needs to be sloped so that the heated water rises to the top of the tank for good flow.
Don't overdo heat pickup at the stack. If you cool the stack too much, you will get excessive creosote build up in the stack.
If you are picking up a lot of heat, the tank insulation might be left on to get truely hot water, or without insulation, the tank could operated as a heat buffer, continuing to release heat after fire goes out.
If you want the old tank to last, check/replace the anode.
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This is pretty much what I was planning to do. I am wondering if 1" diameter copper is too big? Or would 1/2" diameter be better? Or does it matter?

I don't think, but not sure, this will be that much of a concern as the copper tubing will not actually be contacting the stack. I normally keep a good hot fire going with well above creosote making temp (I use a magnetic stack flue temp guage) unless I'm letting the fire go out and then it would be just hot coals and embers burning out.

That's more than I could hope for.......

I just got done scraping and cleaning the old anode. It was in quite good condition. Nothing was eaten away from it at all. After 30 years I've only took it out and cleaned it once. The last time was well over ten years ago. We are lucky to have fairly mineral free water, probably why the old heater lasted so long. I also just flushed out the bottom of the tank and the crud level was still below the drain outlet of the tank. We do have a whole house water filter and water softener.
Thanks again! Steve
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You need a LOT of copper tubing out over the wood stove to pick up any appreciable heat. Think refrigerator coil-style. Back and forth back and forth
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Tempering tanks are a very good idea--however, not with an electric water heater. Do a search for Legionaires Disease and you'll find that almost 30% of homes with electric water heaters have Legionella bacteria growing in their tanks.
The reason electrics have the problem is because they heat from the side. That leaves a cooler zone at the bottom of the tank. The bacteria feeds on sediment and cooler water--anything under 122 degrees.
The experts recommend upping electric water heaters to 140 as the only way to effectively kill the bacteria.
Since gas water heaters heat the water from the bottom, all the heat goes into the sediment, killing the bacteria.
Here's an excerpt from a scientific study:
Like other authors (3,4), including the World Health Organization (WHO) who published a recent monograph on the Legionella problem in drinking water (3), we believe that there is evidence for the transmission of legionellosis through the drinking water distribution systems in private homes. This is a serious illness associated with high death rates (up to 12%). Primary groups at risk (the elderly, smokers, the immunocompromised and patients suffering from chronic respiratory illnesses), are groups who include a large proportion of the population at home. Although we support prevention against tap water scalds, we are against setting water heater thermostats at 49°C because we believe this could facilitate proliferation of Legionella inside the tank and increase the risk of legionellosis.
Domestic water heaters, particularly electric devices, can certainly be contaminated by Legionella. In Quebec, a study of 211 homes (178 electric water heaters, 33 oil or gas water heaters) found Legionella contamination in 40% of electric water heaters. No water heaters using fossil fuels were contaminated (5). The authors concluded that, because of design variables, use of an electric water heater was the most significant factor leading to Legionella contamination in hot water (5) in the home.
Here's the complete link to the study: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid 94925
If you want more info, google legionella electric heater
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BOY! now here's some paranoia gone to seed...... I'll bet you think 911 was an inside job also eh?
s

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I love it. Someone points out a scientific study and the messenger gets accused of being paranoid. This is a serious problem and there have been at least two dozens of studies on it all over the world. It affects about 1/3 of all residential electric water heaters. It's written up on the Centers for Disease Control and the World Health Organization websites. It kills people--literally. So maybe you should think twice about mocking those who bring up a serious potential health problem.
You can disagree all you want about the heating elements, but what I stated wasn't opinion, it's fact. The scientific studies show that the water at the very bottom of the tank can be almost 20 degrees cooler than water near the lower thermostat. So your opinion is really irrelevant to this discussion.
The fact that you've never heard of this before is also irrelevant.
Water heater manufacturers recommend setting the T-stats at 130-140 degrees. That's much higher than in years past--before they discovered the Legionella bacteria. The higher temps set up a potential for scalding. The scalding issue is why plumbing codes now require mixing valves in the shower. Some local communities require mixing valves at EVERY faucet.
If this was no big deal, there would be no need for the higher temps and no need for anti-scald valves. You could set your water heater at 104 degrees, which is plenty hot for a shower.
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well even IF all this is actually true, i guess i don't have to worry.
1. I don't have electric in my own house 2. I always set them at at least 140 degrees.
s

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wrote:

That's what I was wondering too. In other words, what does this have to do with a tempering tank? If it takes 140 deg to make hot water legionaire free, then just set the electric water heater to 140 deg whether you use a tempering tank or not.

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It should be set to at least 140 regardless of your paranoia level. You can't wash dishes properly at any less.
s

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wrote:

Clean dishes, legionares, aids, syphlis, Nile fever, paranoia. I heat water in my place and apartments only as hot as needed to take a good shower. It saves money and nobody gets sick or complains. My next gas bills might be near 4000.00 I pay to much already to waste money on heating water more, which literaly is $ down the drain. Dishes are clean for less $ and Ng is saved. 140f is harder on pipes than 120, scale builds much quicker, leaks occur more often, valves dont last as long, water heaters last longer.
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to the OP re the tempering tank... in the winter, the energy used to warm the water will be taken from the heat that would have heated the basmeent, if you have excess, then fine go for it...
but what i really wanted to asay is in any case please be sure to include temperature pressure relief valves both on the tempering tank and the main tank especially if you are setting up your valves to be able to bypass one or the other.
The last thing you EVER want is a sealed tank with water and a source of heat..
Mark
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On Dec 24, 11:30am, snipped-for-privacy@yahoo.com wrote:

I have plenty of excess heat in the basement. It's like being in Arizona in the summertime.......

I definitely still have the T/P relief valves operational on both tanks! In fact, I was wondering if I should pipe in a small thermal expansion tube into the recirc line?
Thanks, Steve
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Interesting....... If there is some possibility of this happening, I am wondering why it has not been made more of an issue to the public????? There have to be millions of electric hot water heaters in use in this country and I would bet that a very large % of them are set at or even below 120 degrees F. That temp is what most if not all new electric heaters are factory set at. I guess the burn concern is greater than the bug concern........
Steve
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