Water doesn’t go “bad” per se. If left in a container long enough, it goes flat (mixed in air exits) and will taste bad (compounded if stored in HDPE or other suitable plastic). The residual chlorine can evaporate from the water but I think it’s safe to assume the water won’t become infested with bugs if it was stored using reasonable precautions (i.e., don’t take a swig from the container to test quality prior to storing—backwash happens!). There may be some risk from chemicals in HDPE or other plastic containers leaching into the water during long-term storage and this can be reduced by rotation and keeping the containers out of heat/direct sun. However, I’m not convinced the benefit of rotation is worth the labor.

In essence, if water is stored for years in plastic, it may not taste very good and it may have some chemicals in it (probably less than your average pint of “fresh” strawberries), but I’m relatively certain that it will still beat the snot out of death by dehydration. If you’re worried about bugs, keep some non scented bleach on hand and dose it before drinking (but let the bleach evaporate prior to filling your cup).

Question: if the chlorine in water evaporates out of a closed container (let's say glass with a ceramic lid), where does it evaporate TO?

Sue

Chlorine, itself is a gas and can be used for chemical disinfection, generally on a commercial basis. What most of us have available is a solution of sodium hyperchlorite (NaClO) or household bleach, which works through oxidation. As with many solutions, the individual ions will be in a state of flux. In the scenario you have presented, if the container was overfilled, ensuring that no air was present in the container when it was sealed (must be air tight), there would likely be no significant loss of chlorine. However, as soon as you opened the container, a degree of off gassing would occur. If the container was not filled all of the way or if not air tight, additional off gassing would occur.

Pete

Okay, Pete, thanks! That makes sense.

Sue

Another thing occurred to me: occasionally, municipal water is contaminated. I read about towns having to require everyone to boil their water for some reason or other for a few days. If you have a few score gallons in your hot water reservoir, you'll need to clean that out.

The other issue is cross contamination from water and sewage mains. In our area, if we have an earthquake, the water pipes and sewage pipes are likely to be ruptured, resulting in contamination of the water supplies, even if you have some water pressure. You then have your couple hundred gallons with some raw sewage in the supply.

Everything's a compromise, so you get to make your analysis and use your judgment as it applies in your situation. Then you get to live with your decision.

Regarding Arney's observation on the siphoning issue...many municipalities have requirements for backflow preventors to be installed on water lines to larger buildings.

Typically this is with multistory buildings and prevents the water from returning back to the municipal systems if/when they have low pressure events on the municipal mains lines. I've also seen these required when people install a separate irrigation water meter for residences and businesses.

In south Florida, these backflow devices are required to be inspected on an annual basis. Depending upon the chemicals in the water, the valves can have a limited lifetime. At work the eight inch main potable water and fire line back flows have been rebuilt twice in about fifteen years.

Regards,
Comanche7

Well, it is sounding more and more to me like this might be a viable water storage alternative. Relatively low maintenance, relatively easy install, not terribly expensive, and reasonably safe.

Excepting for space limitations, and perhaps some code enforcement issues, is there any good reason not to deploy this set up for home use, allowing for some means of front end/back end sanitation measures?

So this major water main break in the Boston area highlights the one drawback to a water storage arrangement like this--contamination. Which is not necessarily that big a deal if you're prepared beforehand. It's just another step that needs to be taken care of. Anyway, by the time the "boil order" went out in the Boston region, I think you have to assume that the water in your extra tanks have already been contaminated.

Hmmm, it does raise the question of how to clean the tanks once everything is back to normal and clean water is flowing again. Nothing that difficult, but not as easy as disinfecting a small plastic jug.

Not necessarily, but even if you have to boil the water first, at least you still have water to use.

Hot water tanks are easy to purge and clean. Open the bottom taps, flush, shock, flush, test, repeat as necessary.

I suspect that when the main went, the contaimination wasn't immediate, and one could've stood a good chance of shutting off the input before the contamination came through. If one had a monitor/filter/treatment system on the front end, likely the contamination wouldn't have been an issue. But even without all the pre-emptive precautions, contaminated water could still be used in the household for some things. There too, it would depend on what the contamination consisted of.