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Sulaiman
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There is a big difference between drinkable water
(Rainwater or glacial melt water, rivers, lakes, aqueducts, reservoirs, cisterns, tanks, pipes.......
which contain variable types and quantities of 'contaminants' that are generally considered to be acceptable or desirable,
and 'distilled' water for analytical chemistry,
the type that I buy is distilled then 'polished' with ion exchange resins,
which is cheaper than diy.
A great deal of chemistry can be done with rainwater or municipal tap water,
the main contaminant for Rainwater is CO2, with some airborne dust, bacteria etc. but negligible dissolved solids.
Municipal water has chlorides and/or fluorides, iron, and much more.
eg here is a water quality report for my UK home
https://www.south-staffs-water.co.uk/household/my-water-supp...
In Malaysia (my other home) biological contamination of municipal water is significant due to the temperature, it is reduced by chlorination, but
water is boiled (or treated with filtration) before drinking.
At the moment I'm in Morocco, most cities and towns have private or municipal water supplies,
but like much of North Africa and the middle East, older homes were designed to catch rainwater and store it in a cistern... protected from daylight.
Seems to have been successful for centuries or millenia 
If you have space you could consider a solar still https://en.wikipedia.org/wiki/Solar_still
For cheap distillation maybe use a metal pot over a fire made from whatever you can find to burn
(wood, paper, used cooking oil......)
CAUTION : Hobby Chemist, not Professional or even Amateur
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SnailsAttack
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Some new findings:
Fresh snowfall is a nice way to gather a lot of rainwater without having to lay out a big fancy collection system. I just skim the top layer off our
cars into a big bucket.
As it melts you can pick out any little bits of organic debris before they have a chance to leach impurities into the water.
However, I still had issues. Firstly, the filter (a simple paper towel pinned against a mesh) somehow kept getting completely jammed on an extremely
small amount of impurity, which was strange.
Secondly, with no added disinfectants, the dirty-water smell manifested within just over a week; even hours-old snow is a vector for germs,
apparently, which raises some interesting questions about why the entire Earth isn't choked in dirty-water smell.
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Sulaiman
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Food chain?
CAUTION : Hobby Chemist, not Professional or even Amateur
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SnailsAttack
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Also, shoutout to the 12 and a half atoms of cobalt that sustain their entire ecosystem. The devil works hard, but chelating proteins work harder.
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unionised
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Quote: Originally posted by SnailsAttack  |
...
Secondly, with no added disinfectants, the dirty-water smell manifested within just over a week; even hours-old snow is a vector for germs,
apparently, which raises some interesting questions about why the entire Earth isn't choked in dirty-water smell. |
UV light and oxygen
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EF2000
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Mood: Taste testing the Tonka fuel
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The problem with snow is that snowflakes form around aerosol particles. Supercooled water droplets wait for something to freeze on. Those particles
are what jams a filter.
Ice self-nucleation occurs only in pretty cold clouds, so if you live not somewhere in Oymyakon, your local snowfall is most likely from a warmer
cloud.
Studies of snow samples show that biological particles are pretty widespread nuclei for snow. So, snow doesn't get colonised by bacteria after
snowfall, it carries its germs with itself.
Attachment: christner2008.pdf (109kB)
This file has been downloaded 272 times
Wroom wroom
"The practice of pouring yourself alcohol from a rocket fuel tank is to be strongly condemned encouraged"
-R-1 User's Guide
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pneumatician
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Mood: ■■■■■■■■■■ INRI ■■■■■■■■■■ ** Igne Natura Renovatur Integra **
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boiling the water don't disintegrates the chaos in the air dissolved and carried by rain water when the rain drops fall...
make a cultivation and see what type of shit grow in agar... then use a disinfectant tolerable for the use you want for the rain water.
Else use a wide spectrum disinfectant and good luck! because now you have water full of shit and disinfectant! :-)
snow?? this is the worse "water" you can use, layer over layer of shit!
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SnailsAttack
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Brief addition to this post, on the subject of bacteria:
I collected some rainwater from fallen snow about 3 months ago and have since stored it in a plastic jar, kept at room temperature away from sunlight.
It has a slight smell and some milky-white organic precipitate settled at the bottom, but is chemically very pure; content of dissolved solids was
measured at least below 0.005 g/L.
Two days ago I stirred up the jar and plated some samples of the water on a blood agar plate and MacConkey plate to investigate the presence of
bacteria.
The blood agar plate exhibited heavy growth and a number of colony species exhibiting mixed modes of hemolysis. To put the amount of growth in
perspective, I had also plated samples from an abscess on my shoulder which produced maybe a third as much growth.
The MacConkey plate (which isolates for gram- bacteria) also exhibited considerable growth of at least 3 distinct species, negative for lactose
fermentation.
The colonies on both plates were largely catalase positive. No pigmentation.
I'll look into some methods of disinfecting the rainwater without fouling it with dissolved solids if I can sneak a few more agar plates from the lab
at school.
[Edited on 4/2/2025 by SnailsAttack]
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fx-991ex
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I dont want to hi-jack this but i ot a related question.
At the cottage/chalet, we keep rainwater in the summer and add some pool chlorine(tcca), we only use it to wash hands and wash dish, do anyone think
washing dish with it can cause problem?(we boil part of it and add some cold water just to cool it slighly as not to burn our hands). So far it has
not made us sick but id like to avoid getting sick if possible.
[Edited on 2-4-2025 by fx-991ex]
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MrDoctor
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I see it got largely glossed over but, birds like to hang out on your roof, where they poop, in this economy, yes, and with the avian flu still
active, idk if the american one is the same as the australian one with the 50% mortality rate (according to the TV news anyway), i would be
considering that.
Also, i live in an awful rental house, so let me tell you something, long gutters hold water. the older or worse the place, the worse they hold water
since over time with poor maintenance they will sag, resulting in more water collecting. it doesnt take much for an ecosystem to spawn in that gutter,
especially with even minimal organic matter like dirt or leaf litter. prior to the recent cyclone i flushed out a colony of tadpoles from my gutter,
and pulled out a long patch of well developed grass and even a 30cm wild fig tree sapling. my case might be a bit extreme but your guttering will be
like a culture-pond depending on what the weather was like.
Also, for those not familiar with germ theory, bacteria is everywhere outside of antarctica, or above the cloud line on snowy peaks, if microbe-spores
(mostly fungi but still) were large enough you could see one glisten in the light with the ideal light souce, angle, etc, the world would be in a
perpetual haze and youd barely be able to see anywhere in any reasonable distance.
Naturally all sorts land on your roof, dirt and dust land on your roof, etc. In absolute terms, everything is filthy and the world needs to burn, but
in reality, its inconsequential as we tolerate all but a very specific set of microbes, furthermore few are able to make use of the limited resources
to be problematic to us.
On that note, to deal with those problem microbes, where i lived out in the country, peroxide was used. its also a good idea to give your roof a
yearly pressure-washing, the gutter too, once scum builds up in the gutter, its constantly seeding the water.
Peroxide has a pretty short half life as long as spores are there. spores contain enzymes to resist peroxide, presumably for sun-resistance, go try
putting some on literally any green mold on say, some moldy bread, it will fizz up like you soaked it in permanganate.
But its not like you cant toss a piece of human-inert catalyst in there too to shorten how long it is active. Peroxide pretty much eliminates most
bacteria and, really anything that doesnt form solid substrate colonies like mold or algae, though it will devastate those too.
Long metal pipes and the turbulence of your rainwater pump, assuming your tank connects to the home plumbing, will probably also deal with trace
amounts before it reaches your faucet. rainwater treatment bottles come with instructions and protocols, go read them. peroxide is pretty much your
only choice if you want something that technically leaves no residues.
Dogs are apparently VERY sensitive to peroxide, it makes them nauseated and vomit easily, so keep in mind that whatever the treatment protocol is for
you, your dog should probably stay off the rainwater for longer.
Also, degassing isnt practical but, you can get portable submersible ultrasonicators, its just the same element from a stronger bath cleaner but
everything is housed in a weird buttplug looking shell on the end of a cable. i got one for cleaning my glassware and doing reactions since i can just
put the sonicator in a plastic bucket of water to transmit ultrasonic energy safely into a beaker or whatever. same with cleaning, no risk of breaking
anything if it touched the bottom of the bath. putting one of those in your tank and running it each time it rains will also degas the water to some
degree, as well as dealing with any mold or algae or other scum. ultrasonic waves also disrupt/kill a lot of living microbes too, personally i wouldnt
do it except as a treatment protocol alongside say, phosphoric acid like star-san, since its going to liberate a lot of gunk, unless you have a good
filter that is.
UVC sterilizers probably wont work too well,
lastly, slapping a 0.3uM water filter on a dedicated drinking water faucet ensures no microbes can get through, its actually that simple, basic water
filtration setups have biological filters sometimes, maybe consider one? activated charcoal deals with toxins, and while at it might as well get one
with a remineralizer, there exists fancy salts that can give your rainwater a flavor profile like bottled spring water. When i was living on rainwater
tooth demineralization was an issue.
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Mateo_swe
National Hazard
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I would distill the rainwater if i wanted pure water for experiments.
If you have a vacuum pump you need almost no heat, depending on how good your vacuum pump is.
Or just buy the distilled water, if that is an option.
Using UV or other sterilization methods may kill the bacteria but it will leave junk in the water that may interfere with your experiments.
If the water is for consumption it´s another thing completely.
Drinking water contain a lot of minerals and stuff that is beneficial and needed.
You should´t drink distilled water, its too clean and our bodies need the minerals and other stuff in drinking water.
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SnailsAttack
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In the two years since I made this thread I've decided that the method of collecting rainwater by melting fresh snow is definitely better than
collecting rainfall. It's more practical and has fewer impurities.
When filtered, melted snow consistently yields a small amount of black-brown precipitate that eventually jams the filters, but otherwise doesn't
present much of an issue, and doesn't appear when filtering the snow-water a second time. It's most likely some atmospheric soot that the snowflakes
nucleate on.
On storage, the double-filtered snow-water sometimes generates a very small quantity of white bacterial mats/fibers that settles to the bottom of the
container, but this is easily removed by decantation and filtration.
I still haven't properly tested the efficacy of hydrogen peroxide as a disinfectant, but I usually add a few drops anyways for good luck or something.
[Edited on 2/13/2026 by SnailsAttack]
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teodor
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Rainwater has some conductance due to adsorbing water from sea/lakes etc which is present in atmosphere as a small droplets moving by wind, so the
atmosphere is not a perfect distillation column. And this conductance caused by essential cations and anions required by common life forms (because
they are result of evolution and require exactly what is there) as well as CO2 and other gases, but CO2 is that part which will be converted to
organic structures. Distilled water contains CO2 but doesn't contain the minerals - K, P, N - they are essential minerals for metabolic pathways, so
nothing can grow there. Because the conductance of rain water is very low the amount of minerals in rain water is low which makes it quite suitable
for many chemical purpose but enough to maintain CO2 -> organic conversion (one bacteria die and another reuse the minerals). There are some
cations, like Cu2+, Ag+, Co2+, Cr6+ which would disturb bacterial metabolism. Adding those in the same concentrations as, let say K+ in rainwater (the
micro-nano scale) will make no additional harm (it is not distilled water in any case) but will block all metabolic pathways.
I think those cations which are most rare in water should work better. But it is awesome how fast evolution can go in bacterial colonies. Over the
time they can find another type metabolism in their genetic library, so this is a really experimental science.
[Edited on 13-2-2026 by teodor]
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