Hi,

I am planning to store water in 20L Jerrycans.

Do I need to treat the water with some kind of additive (chlorine, iodine, etc.) in order to prevent the growth of micro organisms ?

The idea is to replace the water every 6 months or so.

Yes, you do. It's addressed in the main ETS website. I forget exactly, but it's something like 1ml bleach per gallon (4 L). It's not a whole lot, but I'd reference the main site before taking what I just wrote as gospel.

the standard recommendation is 8 drops of unscented regular strength.. (5 1/2 to 6% sodium hypochlorite bleach (Clorox)) per gallon of clear water, 16 drops for cloudy water....there are approx 18 drops per milliliter...but I've seen other numbers

Thanks for the replies.

My personal view is that if you are storing clean water in a clean container and storing it properly, the risk of anything growing in your water is very, very small. And even smaller if you are changing the water at six month intervals. Properly stored water should have few microorganisms to start with, and no nutrients to sustain them in storage, let alone promote an increase in their population.

However, I think it is a good practice--just to be safe--to treat the water as you use it. In other words, I don't treat my water when I store it. However, if I do have a reason to start drinking my stored water, then I will treat it (my choice is bleach) at that time. But I have had water that was stored for a couple years straight from the container with no problems, too.

You do not `need` to put anything in your water to store it. This is especially true if it's "CITY" water, which has already been treated.

Store it in a cool, dark place.

Ready to use?
Open it, and then put in smaller container. Shake it to introduce oxygen through the water again, and then enjoy.

I agree with you under with one caveat, only in new, clean, enclosed containers made for water storage. Open buckets (remember that you are not the only creature that will seek water), old milk jugs, or other used food containers for water storage can be dangerous, as under certain temperatures (40 to 140 F) bacteria can grow in the trace food residues and excrete the toxins that cause food poisoning.

As mentioned, I'd strongly suggest you read Doug's "Disaster Prep" section at equipped.org. He provides some very specific recommendations.

What? From municipal water, and not a home well? Do you know how he stored the coolers?

Wow, if algae can grow in coolers not exposed to sunlight...there's gotta be significant fertilizer run-off or something in the water that the algae are feeding on, I would imagine. That's a surprising outcome to me, especially after just a week.

I would fully expect that all U.S. city water systems chlorinate the water to sanitize it (typically to about the same concentration as a well-maintained swimming pool, about 2-4 PPM).

The most likely cause is that the jugs, though new, weren't sterile. It is also possible - but unlikely since city water tends to sanitize plumping on-going - that your friend's plumbing is severely contaminated. It can happen.