When rainwater is stored in a barrel, how soon do you have to use it up before the algae forms?

If it had algae can you still drink the water?

Do clear storage containers promote algae growth more so than black?

I use the rainwater even if has algae in it for watering the garden, but if it's too funky, I just use it on trees or the non-food plants. As far as drinking it...I don't ever drink rainwater. My rainwater comes off the roof and too much bird poo, dust, dirt, soot, etc. I know in an emergency, water can be solarized to purify it, but I think it's a very bad idea to drink it. Years ago, maybe, but not now. As far as how long it takes for the algae..depends on temperature more than anything else. I don't have a clue about the colors making a difference. I would think that the black ones would get hotter than other colors. Does that kill the algae or promote more rapid growth? Something to ponder.

I might put some fish in the barrels to eat the mosquito larvi. There are also fish that eat algae.

I would not water people or critters with cistern water. Plants yes, vertibrates no.

Generally the Algae will form in about 5 days in water that is still, undisturbed. Once the Algae forms and attaches to the sides of the container, it will reappear again sooner unless the container is cleaned really well between uses. Since allof our water comes from sources where Algae grow in that water you do already drink water that has had Algae in it, although what you drink and use has been filtered, even those of use on well water have our water filtered (unless you pump it directly out of a pond or cistern). I've not seen that the type of container has much if any affect on the growth of that Algae, and I'm not sure I'd drink water that did not grow Algae because that would be sterile water, dead water.

There are so many forms of algae. Are you, Kimm, implying that the algae in cisterns and rainwater barrels, ponds, stagnant water is the same algae found in our wells? I was under the impression that the algae in wells is considered "safe". I think also, harmful bacteria will be growing along side of the algae, probably some mold and fungi as well. My well has been shocked twice in maybe 50 years and I have no filtration system whatsoever. Even with a filtration system, I would not drink water containing algae if I didn't know where it came from (not including wells). If the water has been purified, i.e., a municipal water treatment plant, certainly that is considered safe. As far as "sterile water", I think distilled water would be acceptable to drink. It's not mineral water that's for sure, but it would do a fine job of rehydrating if you were thirsty.

Thanks.

Sterile water - guess that is why my stored city water never forms algae. Had no idea non sterile water forms algae so quick. Its sounds like algae in a water source may not hurt us from what you say?

The bird poo and junk from the roof is a different story though - never thought about that stuff.

From some recent readings from the 1930s, with the old rain water cisterns they used to keep the valve to the cistern closed by default.

Had to let the rain wash the roof first of bird droppings, wood and coal ash from heating, etc.

After opening the valve, the water should go through a screen to remove the big stuff, then at least a sand filter, and if you could a carbon filter.

And you still had various chemicals to use on the water in the cistern, and flocculants like alum to use to settle out pollutants. And once a year get to go in and clean out the bottom.

A lot of work.

There are many forms of Algea, and the ones that form in lakes, streams, and ponds are the same as those that would be in well water and that can include the toxic Red or Green Algae formed in water sources with a much too high Phosphorus concentration. The same Algae that forms in your birdbath,if you do not change the water often enough, can be in the water from your well, or municipal water system. The wee buggers that form that Algae are in the water, unless the water is treated so heavily that they are killed off.

When I was first married years ago, we used a spring, built a spring house, apparently not a very good one though. We cleaned it out every year, but one year, the water started smelling terrible, like something rotting...which it was. We went down to clean it out, and there was a dead rabbit floating in the holding tank. We drained the tank, got in there and scrubbed and filled with water, poured in bleach, drained, rinsed and did some major repairs so it didn't happen again. We also drilled a well, and used the spring water for the garden, washing cars, etc. You have to be so very careful with your water supply. We were lucky that we didn't get sick, or worse.