# Bacteria Growth



## Virgil (Sep 29, 2009)

Does anyone have any comments concerning the potential of bacteria growth within an open loop, at atmosphere, drain back thermal system..??. The Legionnaire's Disease potential...


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## Ky-Jeeper (Sep 5, 2010)

Algae?


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## sevenmmm (Mar 1, 2011)

Legionella bacteria is normally found in water 115 to 120 degrees. August is the worst time of the year for outbreaks, which makes some sense as this is the hottest time of the year. This bacteria, and others, can and do live in all of the aforementioned systems including tank water heaters fueled by conventional means.

In an open loop system, the water flowing into the collectors can harbor bacteria. The key is to keep the water flowing not allowing for water to stagnate anywhere in the system, and allowing for the system to be sized to produce higher than 160 temps - which would kill the bacteria. It is very difficult, if not impossible to size an open loop to maintain a constant 160 temperature. Overheating - solar can even boil water! - would be an issue that would lead to system failure, or worse, 1st degree burns. 

The water in an atmospheric tank never comes into contact with the potable water supply, so this can be ruled out as potential threat.

The drain-back is the best all around system, including the ability to oversize the collectors relative to the amount of water needing to be heated. In this system, the controller would shut off the pump once 160 degrees is reach. The solar fluid would then drain out of the collectors and into a special drain-back tank installed in the solar loop and located near the solar storage tank. Thereby stopping any further heat build-up in the solar tank. 

Worthy to note in this context, a cold water mixing valve absolutely should be installed after the solar storage tank and hot water heater. Normally this would be set at 115 degrees. Having your hot water heater full of 160 degree water allows for more solar-heated water storage, and will also kill the bacteria in the water heater.

http://www.cdc.gov/legionella/patient_facts.htm


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## woodsy (Oct 13, 2008)

Virgil said:


> Does anyone have any comments concerning the potential of bacteria growth within an open loop, at atmosphere, drain back thermal system..??. The Legionnaire's Disease potential...



Interesting topic.
I researched this some awhile back and couldn't find anything reported about 
Legionnaire's disease caused from solar hot water drainback systems.
My solar DB tank is pretty well sealed and not situated in a living space but is in the basement.
Keeping the DB tank sealed tight would be my recommendation if you are worried about it.


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## SolarGary (Sep 8, 2005)

Virgil said:


> Does anyone have any comments concerning the potential of bacteria growth within an open loop, at atmosphere, drain back thermal system..??. The Legionnaire's Disease potential...


Hi,
Are you asking about the possibility of Legionnaire's in the potable water part of the system or withing the heat collection part?

Gary


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## Virgil (Sep 29, 2009)

Within the heat collection part...


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## SolarGary (Sep 8, 2005)

Virgil said:


> Within the heat collection part...


Hi,
Just going by what they say here:
http://www.osha.gov/dts/osta/otm/legionnaires/hotwater.html

It does not seem like the large, EPDM lined syle of drain back tank has the conditions that lead to Legionnaries growth (that is sediment, dead ends, and cool places). And, it seems like the water in the tank is going to be heated up to a temperature that kills Legionnaries fairly often. Since no new water is introduced into these tanks on a routine basis, reinfection seems unlikely?

I guess if one were concerned about it, a biocide could be added once in a a while. 

Since the collection system is separated from the potable water, the risk seems minimal?

Apparently there are lots of regular hot water heaters that have Legionella:

"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."

From: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2094925/
This seems like more of a risk?

Gary


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## sevenmmm (Mar 1, 2011)

I believe a properly sized drain-back would pose the least risk. These type systems can be over sized - the reason for the drain back feature - and this will accommodate high enough temperatures to kill the bacteria both in the potable water and the solar fluid.


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## Virgil (Sep 29, 2009)

Very good comments from all and the web sites indicated were reviewed. It is interesting that in the Quebec study that the standard electric water heaters were prevalent for the Legionella contamination. 

From all the literature and related web links it seems that long term stagnation of the water within the pipes and storage tanks in the temperature range of about 110 to 120 degrees Fahrenheit is the chief breeding ground for such bacteria. And agrees with the postings from you folks. 

A brief description of our drain back solar collector system: It is an open to the atmosphere collector loop. While the water pump is running air is continually entering the collectors via one way valves located at the highest point of the collectors. The collector pipes are all 3/4" copper in serpentine configurations. The storage tank located in the cellar is a blue poly-plastic, high density, 50 gallon barrel. A differential controller does not allow the tank temperature to exceed 140 degrees Fahrenheit. Two parallel connected 3/4" copper coil heat exchangers are immersed within the water storage tank. The interconnecting pipes and storage tank are all insulated. 

The return water pipe from the collector is intentionally placed above the expected highest water level within the tank. While operating gravity produces the water fall turbulent effect as water reenters the storage tank from the return line. Under this operating condition it would be assumed that the recycled water within the collector loop is well oxidize.

The tank water for the collectors was obtained from the local municipal supply. It is chlorinated. 

For approximately three years the system has operated with no visible algae, mold, mildew, nor objectionable smell within the storage tank. The tank is usually drained and fresh water added once a year. Condensation does occur on the inner wall of the tank's outer foam board enclosure. 

Apparently, copper ions in low level concentrations in water in this case the oxidizer is a disinfectant. As quoted from the website, ingentaconnect.com, "Copper ions have been used to disinfect liquids, solids, and human tissue for centuries. Today copper is used as a water purifier, algaecide, fungicide, as well as antibacterial and anti-fouling agent.Copper also displays potent anti-viral activity. " Note from Wikipedia.org web search. 

Likewise, high concentrations of copper oxides are an irritant. Inhalations of powder or fumes in extreme cases as during smelting operations are very dangerous. 

Copper at proper levels is an essential ingredient for the human metabolism. Copper oxide is used in vitamin supplements, consumer products such as bedding for its anti-microbial properties. Which comes to mind is the clear fountain water where hundreds of pennies, nickels, and quarters had been tossed into the wishing well. 

Therefore, for this open loop drain back system would the forced oxidation of solar heated water rushing through out the copper pipes and into a storage tank containing coiled copper heat exchangers be in itself a water purifying anti-bacterial system ??

Any comments ???

Virgil


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## sevenmmm (Mar 1, 2011)

A drain back can not ever be an open loop. An open loop would always be under pressure from the well pump or from a municipal utility and would not be able to drain...., back. 

A drain back is designed that either the collectors are filled with flowing fluid, or air, when the fluid is allowed to drain back into a tank located in the solar loop below the collectors. Preferably (but not necessary) in a heated space. This can only occur with a closed loop system.

Also, it should be of interest that a perfect system may use straight water even in freezing conditions. However, there is precious little time before the water would freeze in the draining, hence perfection. So a mixture of water and a non-freezing heat transfer fluid is recommended. 

I have my drainback tank in a heated space and at 13% DowTherm to water mix here in Wisconsin.

http://www.dow.com/heattrans/solar/


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## Virgil (Sep 29, 2009)

I had typed in a reply... However, the system or Verizon kick me off line..as I tried to post the reply.... I will try again at a later time.... Does anyone know how I can save a posting before actual attempting to make the post...????? This as happen to me before.... We are stuck at this time with Verizon...so changing that is not an option... 

Virgil


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## woodsy (Oct 13, 2008)

> =Virgil;5494304] Does anyone know how I can save a posting before actual attempting to make the post...????? This as happen to me before.... We are stuck at this time with Verizon...so changing that is not an option...


Copy it before submitting, in case you get logged out by HT and lose the post

To copy.... highlight the post , hit ctrl C

To re-insert hit ctrl V.

If its verizon kicking you off line then open a seperate tab/page which should keep you from losing the post also. 

use the copy /paste method again if need be.


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## Virgil (Sep 29, 2009)

Oh gee Thanks Woodsy.... for that information .... I have made a copy of the information and will keep it near the online computer.... Thanks again.... 

I am going to try to keep my posting shorter due to the recurrent problems of doing posts to this website... for now... 

Now back to the solar question... First of which, It seems I need to back up and clarify that this system does indeed inject atmospheric air into the return manifold on a continuous basis... And the water does drain back to the storage tank immediately when the pump shuts off... When I stated that on the original thread inquiry I assumed that everyone understood what I was referring to... evidently not... 
More to follow... 

Virgil


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## Virgil (Sep 29, 2009)

Hopefully, the following explanation will be clear enough for everyone to understand how the dynamics of our system operates. I will probably need to break up this explanation into smaller text bits through multiple postings...

Situated on riser pipes at both ends of the return water flow manifold are two horizontally mounted mechanical one way valves. Additionally, two spring loaded vacuum breaker valves are mounted at the same locations. The latter valves are back ups encase the mechanical valves fail to open when needed.

Before the water pump is energized the entire collector piping is full of air. This places the whole system at one atmosphere given the altitude that we are at relative to sea level... This would be the total weight of air above our heads normally measured in pounds per square inch. The air above the tank water level would be equalized to that same air pressure. The return pipe which enters the tank is maintained above the expected highest level in the tank. It's always above the water. 
On to the next posting.... 

Virgil


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## Virgil (Sep 29, 2009)

When the water pump is energized the rising water starts to displace the air within the pipes and collectors. Initially, the one way mechanical valves remain closed due to the back pressure or upward movement of the air in the pipes. It should be noted that the mechanical valves are not air tight. There are no seals within them. The displaced air now is forced back towards the top of the storage tank. This helps to equalize the pressure within the storage tank. This is important so as to prevent a partial vacuum to develop over the water in the storage tank if the tank was very tightly sealed. This normally would not be a problem.

The water floods the collectors from the bottom manifold. As the height of the water increases its weight within the pipes increases the pressure that the pump must overcome. On to the next posting...

More to follow... 

Virgil


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## sevenmmm (Mar 1, 2011)

Never heard of it. Fraught with complexity is my initial response.

Is this a design you thought up Virgil? How long has it been in operation?


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## Virgil (Sep 29, 2009)

The technique is quite simple at equalizing the pressure within the pipes. it is automatic and self-regulating. This will be the fourth winter it has been in operation..

For our system the vertical distance from the top of water storage tank to the return manifold which is above the collectors is approximately 22 feet. The pump working against the force of gravity has pushed the water through all the collector pipes to reach the return manifold. This is often referred to as the vertical head for the pump. 

As the return manifold begins to partially fill with water the fluid dynamics begins to shift. The manifold is sloped towards the vertical pipe which returns the than heated water back to the storage tank. The moving molecules of water tend to stay together. In doing so gravity creates the turbulent free falling water effect as the water flows back down the pipe to the storage tank. The movement of this heavy weight of moving water displacing the air creates a negative pressure drop within the pipe. The atmospheric pressure outside of manifold is more than inside the pipe at this time. This natural pressure difference forces the flapper on the one way valve to swing inward. Air is than sucked into the pipe in an attempt to neutralize the pressure differential. 

On to the next posting.... 

Virgil


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## Virgil (Sep 29, 2009)

The flapper vibrates or pulsates as it increases or decreases the amount of air which is drawn into the system at any given moment. The volume of water leaving a particular collector is a driven dynamic relative to the amount of solar energy retained by the water. At any given time the temperature of the water leaving a particular collector maybe cooler or warmer than the others and hence it's weight maybe slightly different. 

The air which is constantly injected into the return manifold mixes with the water flow. This combination it is believed further oxides the water. 

Next posting... 

Virgil


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## Virgil (Sep 29, 2009)

When the pump shuts off the pressure maintained by the pump to sustain upward water flow is lost. The fluid dynamics drastically shifts again. The weight of the water through out the system causes it to flow back to the storage tank. The steady downward flow of water from all the pipes is only possible by the likewise sudden infusion of air via the one way intake valves. This in flow of air mass must quickly fill the volume displacement once occupied by the water. If the atmospheric air was not allowed to rush into the pipes partial vacuum cavitations could occur. Pockets of water would than be retained within the pipes. Dribbles of water would exit the pipes over time. In subfreezing conditions this could lead to expanding ice crystals and burst pipes. 

Next posting... 

Virgil


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## Virgil (Sep 29, 2009)

Finally, back to my original question, under the conditions of how our open to the atmosphere solar collector system operates does anyone have any knowledge concerning the following:

With air continually entering the collector return loop assuming it increases the oxidation of the recycling water which is in contact with copper pipes in the collectors and the outer surface of the copper heat exchanger coils located within the storage tank would this create enough copper ions in the water so as it is a self sustaining water purifying anti-bacterial environment ???

Comments ???

Lastly, we do have a partially constructed web site with some pictures of our system. It is currently off line. If anyone was interested we could place it back on line for awhile...

Virgil...


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## SolarGary (Sep 8, 2005)

Hi Vrigil,
The system you describe sounds a lot like the drain back systems of years ago when a vacuum breaker was used at the high point of the system to introduce air during the drain back. 

It was found over time that the vacuum break is just not needed for good drain back. As long as the return pipe is of adequate size, the air comes up the return line just fine. The vacuum breakers on older drain back systems would occasionally fail and cause a collector freeze. I believe that nearly drain backs done today are done without a vacuum relief valves.
My two drain backs have no vacuum breakers and have worked flawlessly in our -30F climate for years.

----

There was also mention in one of the comments about using antifreeze in drain backs. I guess practices vary in different parts of the country, but its uncommon to use antifreeze in drain backs around here -- and, its very cold around here. To my way of thinking, if the plumbing on a drain back is laid out correctly, the antifreeze is not necessary and just adds cost and maintenance. 

There is a good article on drain backs in issue 97 of Home Power by Chuck Marken -- I've pasted in an excerpt from it below.


Gary

From the Home Power article:

DB System Operation
The major components of a DB system are the collectors,
drainback tank (aka reservoir tank), hot water storage tank,
heat exchanger, and one or two circulation pumps,
depending on system configuration.
The drainback system is a closed loop system. However,
unlike the closed loop antifreeze system, a DB system has an
unpressurized closed loop, and it does not usually use
antifreeze as the collector fluid. The collectors and
drainback tank are part of a closed loop, which contains
both air and the collector fluid, which is usually water.
When the system is not operating, all the water is in the
drainback tank, located indoors or in
another freeze-free environment. The
collectors and outdoor piping have
only air left in them. That is the freeze
protection strategy.
When the system is activated, the
collector loop circulation pump lifts
the fluid up to the collectors. Once it
passes through the collectors, it
returns to the drainback tank by
gravity. When the system is
deactivated by the controller, the
pump turns off and all the fluid in the
collector drains back to the drainback
tank. Drainback systems require a
high head pump to lift the collector
fluid the full height to the collectors.
The solar heat removed from the
collectors is transferred to the hot
water storage tank by means of a
heat exchanger. Several tank/heat
exchanger configurations are discussed
below. DB system design can be very
simple. If the proper care is taken with
collector mounting and piping, the rest
is a breeze.
---
Drainback systems should always be installed with the
hot return pipe as vertical as possible. The collector loop
piping in drainback systems should be a minimum of 3/4
inch. This minimum pipe size and steep slope allow for air
in the drainback tank to quickly rise to the top of the
collector and break the vacuum that would otherwise hold
the water in the pipe. A well-known demonstration of this
www.homepower.com 49
hot water how-to
vacuum phenomenon is holding your finger over the top of
a common drinking straw filled with a liquid. The liquid
remains in the straw until you remove your finger.
Removing your finger breaks the vacuum by allowing air to
enter the top of the straw, allowing the liquid to drain.

Chuck has installed many many many drain backs, teaches workshops on how to do solar hot water -- he knows his stuff.


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## sevenmmm (Mar 1, 2011)

Virgil said:


> If anyone was interested we could place it back on line for awhile...
> 
> Virgil...


I would like to see it, please. It would also be interesting to know the parts cost of this system, as well as the solar guy's.


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## sevenmmm (Mar 1, 2011)

Oh, I just remembered. My teacher in training school told me never to install one as he has seen a few - in the frigid Wisconsin winter - that burst the pipe and filled the basement with water. I'm sticking with a closed-loop using solar fluid. Sorry I asked.


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## SolarGary (Sep 8, 2005)

sevenmmm said:


> Oh, I just remembered. My teacher in training school told me never to install one as he has seen a few - in the frigid Wisconsin winter - that burst the pipe and filled the basement with water. I'm sticking with a closed-loop using solar fluid. Sorry I asked.


Hi,
I am a fan of drain backs, so I may be a bit biased, but this is my two cents on why I like them and think they are a better solution.

Failures of drain backs are nearly always caused by bad plumbing that does not have a continuous slope toward the tank. If you get the plumbing right they will provide very very reliable freeze protection in the most extreme climates. 

Closed loop systems with antifreeze have their own set of issues. The antifreeze sits in the collector all summer and cooks. This causes even the best antifreeze to degrade and once degraded it will corrode the copper and cause the system to fail early. The antifreeze needs to be tested once a year and replaced if bad. Many people just won't do that. 

Closed loop systems are subject to overheating in the summer, especially if demand is down. When they do you end up with big green puddles of antifreeze where the relief valve is. They are also more complex systems with more components to maintain and to fail.

So, with a drain back you have to get the plumbing right when you build the system, but you only have to do that once. With a closed loop system you have to maintain the antifreeze forever every year.

Drain backs can't be used in all situations, but where they can (I think) they are a simpler and more reliable design than closed loop systems.

Gary


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## woodsy (Oct 13, 2008)

sevenmmm said:


> Oh, I just remembered. My teacher in training school told me never to install one as he has seen a few - in the frigid Wisconsin winter - that burst the pipe and filled the basement with water. I'm sticking with a closed-loop using solar fluid. Sorry I asked.


Just goes to show you can't believe everything you are told.

Happy DB solar hot water system owner, no antifreeze. Installed 2 1/2 years ago, frigid winter climate (lows to-20-30F), no problems whatsoever with the design and performance..

Back on topic,
Virgil, thanks for sharing your research on the potential bacteria issues in solar systems.
I did find that the U.K has some regulations on solar hot water systems because of potential issues.
If i recall correctly, they have to have some in line or in tank heating system that will bring the water temp up high enough 
and frequently enough to kill any bacteria.
But, can't see this would be necessary in a DB heat exchanger type system where the solar heated water never comes through a homes faucet or shower. 
In order to contract Legionnaires disease you have to inhale the mist
or water droplets from the contaminated water the way i understand it.


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## Virgil (Sep 29, 2009)

Good Evening Gentlemen... Yes, Gary I agree and we are aware of the rising air bubble phenomenon to help break up the partial vacuums which could develop in such systems once the pump shuts off. In our situation we felt that a more fast acting and automatic air infusion at the collector site was needed for a couple of reasons. 

We use horizontal mounted sloped serpentine loops within the collectors. The pipes are 3/4 inch copper which were recycled from solar collectors we had built years ago. Due to construction restraints the nearly eight foot long collectors are also horizontally mounted in a low profile position. The newer vertical wall mounted collector also uses recycled copper pipes. 

Unfortunately, all of the water return and supply runs had to be plumbed in long runs outside of the structure exposed to the elements. Not the best of situations but, made due the best we could. We live in the ever changing climate of the Northeast. Dealing with fresh water running through pipes intentionally exposed at times to sub zero ambient temperatures successfully requires a certain amount of careful planning. 

We first started building home brew wooden frame solar collectors in the late seventies. The last ones we built were in the middle eighties and were used for several years until the frames rotted out from within. Treated lumber maybe was not that available than. Metal framed collectors would seem to be better in terms of durability.

Another important consideration for not using pressurized solar collectors is because of our very close proximity to our neighbors. We are within twenty feet of our neighbor's house. Numerous children live in our immediate area. The spraying of hot liquids with or without chemicals from burst pipes from our elevated collectors into the environment would be a potential social and economic disaster. A situation that is best avoided. 

With the multiple air ports located directly above the collectors it is believed that a quicker and more positive flushing of the water from the pipes would be achieved. Therefore, this is the prima facial purpose for the redundant vacuum hindering system. We would rather error on the side of over protection than not. The additional spring loaded vacuum break valves were installed this summer during construction of the vertical collector. They too are backups and to date are untested.

Virgil...


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## Virgil (Sep 29, 2009)

And Woodsy, Thanks for the additional information concerning the U.K. regulations...

The prior comments from all have been a good exchange of information... Though, we seemed to have gotten slightly off topic...But, that's OK...

The information we have exchanged here concerning the possibility of bacteria growth in drain back solar systems seem to conclude that there is a lack of available information. That would seem to me as being a real good thing. There appears to be no smoking gun pointing to numerous health risk cases involving heat exchanger type solar collector systems. If anything, the general use non-heat exchanger hot water heater appears to be at a higher risk for such problems...

It is the air borne vapor inhalation risk which concerns me. That period of time when I have unsealed the tank. Obviously, the use of a filter face mask would be the item to use. 

I would still like to find out definitely if an all copper pipe drain back system would produce enough copper ions in the water to be a natural disinfectant... On the occasions that we have changed the water we have never found any evidence of slime residue on the inner surfaces of the tank or copper pipes. That would be a direct indication of bacterial growth. Over time fine sediment though, will form at the bottom of the tank from the use of the street supply fresh water. 

Perhaps, I'll drift around some of the chemistry forum sites as time allows... I would certainly be out of my element there....

Thanks again Gary, sevenmmm, Woodsy, Ky-Jeeper for your participation and of course, if any of you do come across some additional relevant information we are all eye balls...

Virgil...


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## SolarGary (Sep 8, 2005)

Hi Virgil,

Since you don't likely open the tank very often, how about just disinfecting the tank before you open it?

My tank as half inch diameter open pipe coming out the top that serves as a vent (using a cap with a 1/8 inch hole), as place I can check the depth with a dip stick. One could use the same kind of pipe to add a disinfectant a couple hours (or whatever works) before opening the tank?

Gary


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## Virgil (Sep 29, 2009)

Good suggestion Gary... Before we upgraded to the current tank insulated shell we had a reseal able flapper. It provided limited access to inspect the water level. It was somewhat cumbersome to use. During those times, as I mentioned earlier, we would add a few ounces of chlorinated bleach to the tank, the shot gun approach...

Out initial installation had the pipes routed through the top of the tank. That method proved difficult to seal with a fair amount of hot water vapor lost from the tank. This required periodic topping off of the water level in the tank to compensate for that water migration. 

The input/output pipes are now routed through the upper side walls of the plastic tank. The tank top is sealed with Reflextix bubble wrap and aluminum tape. The amount of vapor lost and condensation on the outside of the tank seems to have noticeably diminished. And with that the retained water level within the tank seems to be more stable. 

The cellar location of where this tank is located would be considered wet to damp. It is also cool. Therefore, a dripping condensation problem does come and go in intensity on the inner surface of the outer shell of the poly insulation board. This problem is a direct indicator of the relative humidity surrounding the tank shell. We do not vent the tank directly.

We do spray the top portion of the tank with Lysol aerosol disinfectant at the time of opening for maintenance and again a shot before the tank is resealed. 

A better support rack for the larger heat exchanger coil is currently under construction. At the time of its installation later this winter I'll consider adding a seal able inspection port. 

Thanks... 

Virgil...


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## sevenmmm (Mar 1, 2011)

woodsy said:


> Just goes to show you can't believe everything you are told.
> 
> Happy DB solar hot water system owner, no antifreeze. Installed 2 1/2 years ago, frigid winter climate (lows to-20-30F), no problems whatsoever with the design and performance..


Sure. I believe there are still some of those working from the 1970's, but I bet there are more that are not!

Nope, an open loop water system is at risk to freeze, and if it does, could fill your house and basement with water (unless you live in your house 24/7 and lucked out you were awake if it did).

Sorry, but with a little research you will find this does happen. It reminds me of those batch systems in Florida that all failed one winter a long time ago. A freak cold snap did them in. This is the reason solar installations stopped dead in its tracks. 

Bad design, won't install it.


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## woodsy (Oct 13, 2008)

OK, whatever floats your boat seven.
Its obvious people who have problems with drain back systems either didn't build and install them properly, or didn't have them built and installed properly. I rest my case.


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## sevenmmm (Mar 1, 2011)

woodsy said:


> OK, whatever floats your boat seven.
> Its obvious people who have problems with drain back systems either didn't build and install them properly, or didn't have them built and installed properly. I rest my case.



Sure. Even with a perfectly installed solar water heating system, of any design type, normal degradation still comes into play sooner or later. I would much rather minimize all the risks and reduce the complexity, of which a closed-loop drain back fits "my" definition.

Perhaps I pushed this discussion off track a bit, but a drain back is the best system which will allow higher temperatures to kill bacteria, yet, have a fail safe built in which will stop the transfer of heat to prevent overheating. Beyond that, one should compare and choose a system with the least likelihood of failure in any given weather and use.


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## woodsy (Oct 13, 2008)

Legionnaires disease cases up in New England and Quebec.
Don't see any mention of solar hot water systems though.

http://www.onlinesentinel.com/news/legionnaires-risein-region-mysterious_2011-11-28.html


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## sevenmmm (Mar 1, 2011)

woodsy said:


> Legionnaires disease cases up in New England and Quebec.
> Don't see any mention of solar hot water systems though.
> 
> http://www.onlinesentinel.com/news/legionnaires-risein-region-mysterious_2011-11-28.html


Nope. You wouldn't either (if you designed a solar hot water system that reaches 160 degrees on occasion). Thanks for the link, another reason to install a solar water heater!


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## Virgil (Sep 29, 2009)

Thanks Woodsy for the updated info.....

Virgil


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