[permaculture] any biologists out there?

Lawrence F. London, Jr. venaurafarm at bellsouth.net
Sun Dec 20 06:23:01 EST 2009

Lawrence F. London, Jr. wrote:
  > The factors affecting the vulnerability of the cheaper system to
> contamination by pathogenic microbes should be considered with an eye to 
> designing and building the more expensive system with the HE; i.e. avoid 
> obvious mistakes and pitfalls with the better system. Standing water in 
> the cheap system undergoing wide temperature swings and remaining 
> stagnant for periods of time may be what creates the environment 
> favorable for the pathogenic microbes to incubate and propagate. With 
> the better system you have water only in the 3/4" lines and what is in 
> the hot water heater which likely presents no more risk for 
> contamination than normal use of that type of heater using an electric 
> element or natural gas - plus you could hook it up to an energy source 
> for backup DHW source.

Another thought. What stimulates the bad microbes too grow in the water 
is water temperatures that are too low for too long and too often with a 
large quantity of water involved stored in a container with questionable 
sanitation. A possible solution might be a few options:
1) insulate the main working external storage tank very well, maybe R50 
to keep the water hotter longer
2) connect the conventional hot water heater used for storing house DHW
(probably the cheapest and best storage tank for the money) to an 
electric source or gas if that is available and simply use
hot water from the exchanger as preheated water to supply the working 
heater to reduce energy use; also convenient as a backup DHW system.
3) instead of using a conventional water heater use a demand water 
heater powered by LP gas, or even electric.

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