Originally Posted by westwinds
Can anyone tell me how long drinking water held in a tank will last before it is no longer pleasant to drink? I know this is going to vary depending on the organics in the water and the temperature. If you have any experience with how long the water takes to go bad, maybe you can tell us what kinds of temperatures you experienced and whether the water source for your tank is from a surface water or a well?
By the way Steve has brought up a point about total trihalomethanes that is not discussed much by the public health
types to the general public. Their belief is that we will get some excess cancers, but the benefit of being able to kill pathogenic bacteria cheaply out weights the cancer problem. I would be willing to pay more for disinfection by ozone or ultra violet. Unlike chlorine, both these disinfectants will kill giardia cysts. A public water treatment removes these cysts by filtration, not disinfection with chlorine. Google
giardia, it is prevalent in fresh water lakes from wild life and you will note that it is not a disease you want to experience. I will use ultra violet disinfection for any water I take on board if there is any question about its source.
The first question is like "how long is a piece of string." The obvious answer is that if the water is properly purified, practically forever.
You are far, far more likely to die of infectious disease than cancer from trihalowmethanes. I consider that to be read herring, or at least a lighten strike sort of fear. Keep your eye on the ball.
1. Neither ozone nor UV leave any resisdual in the tank. Thus, if any organisms survive, and they will, they will multiply out of control. This is not acceptable for a distribution system and it is not acceptable in your tank.
2. UV takes a lot of power for tap use because it must be left on (bulbs have long warm-up time). As for UV treatment before loading, the required treatment unit to kill both bacteria and cysts in unfiltered water (you will have to filter) at 10 gpm is impractical. Folks won't like waiting behind you.
3. trihallow methanes can be minimized by not over-chlorinating. Measure the dose.
There are proven protecoles that are safer and more reliable than the road you are considering. Quite easy, actually.
1. Prefilter to remove solids. Clean the tank annually. Nothing works if the tank is not clean.
2. Chlorinate. Measure the dose, it is actually very, very low.
3. Secure the vent. Bugs can crawl in.
4. Filter NSF 53 at the tap for cysts. If this is done with a carbon block filter it will remove the chlorine and much of the THMs.