Benifits to using rain water?

[TwoStems]

I've noticed a few people recently mention they collect rain water to use for watering their orchids rather than tap or filtered water. Just wondering if there is a significant benefit to doing this, and what the best of way of collecting is.

[orchidlady]

The main benefit is that it doesn't have the dissolved minerals that can cause problems in some areas with municipal or well water that has high levels of dissolved minerals. It is an alternative to using a reverse osmosis system. Many people find that collecting it off a roof works well.

Susan

[Bob]

I've often thought about doing that (collecting off the roof) but what about pollutants in the water, such as in a major metropolitan area like Chicago?
I'm a bit paranoid that it would't be clean enough, especially for Phrags.

[Joyce184]

I read in another thread that many like to water their orchids with warm water. For those that collect rain water (from their roof or by other means), do you do anything to the water beforehand?

[RedEcho]

I like using rainwater because it is free and in my area very clean. My city provided water will kill goldfish within an hour. I cannot imagine what harm it does to my plants roots.

[David Boyle]

It was suggested to me that I use snow water and then rain water (north of Calgary AB). I collected snow and melted it and my orchids improved in amount of growth and vigour quite rapidly. I have just started collecting rain water from the roof. We shall see how that goes. The vendor also suggested that I let tap water rest for a few hours but not for longer than 12 hours. I did not ask the reasons but I assume that what I don't want in the water bubbles off quickly. Then evaporation causes concentration of the rest. I haven't tried this yet. Our normal snowfall and rain comes straight from the rockies so polution is not much of a worry but I would NOT go back to tapwater except for short periods of time.

[Halloamey]

Ali, as Susan already pointed out its because of the low dissolved solids, most common orchids that we grow like CAtts, Phals etc grow as epiphytes (on trees for support) in nature, with not much around their roots apart from a few decomposing leaves and an occasional bird shit. They get the water directly from the rain or the mists and fog which is pure water with just some dust and dissolved gases, the purest form of natural water, so they have evolved to like water that is free of dissolved salts. When the water hits the ground it dissolves the water soluble salts in the soil in quantities depending on each type of soil. In some areas the water is so high in dissolved solids it orchids cannot tolerate this concentration of salts and will eventually die. So an easy and cheap way of ensuring good water for your orchids is to collect snow and rain water.

[Bob]

I've been using tap water that I let stand for as long as a few weeks on everything except Phrags. Paphs, Phals, and a few unidentifieds. They all seem to be doing fine.

[Dorsetman]

They get the water directly from the rain or the mists and fog which is pure water with just some dust and dissolved gases, .

Sorry to contradict Amey, but its not that simple. Epiphytes grow on other plants , and the water they get is not straight from the sky , it is what has landed on other plants, and then trickled down onto the epiphytes. Most plants in active growth express sap from the leaves - the pressure applied to keep the plant erect and turgid results in some " leakage " - e.g. as "honeydew" ( Try looking at your plants at 2 am - there may be surprised how much ther is then ). This gets dissolved in the rainwater, and provides nutrients to the epiphytes.
So I discovered when I sat in the rain forest in Thailand, in the rainy season, and took samples of water from the open sky ( EC as low as 20) and then collected drips from the roots of e.g. dendrobiums - and found the EC was up to 600. I did this at several sites,at different times, from several different genera ( paphs, Coleogynes, etc ) and always found more or less the same thing. My "research" to give it a rather grand name has been published in the orchid journals of UK, The Netherlands, South Africa etc etc ;my "experiments " have been repeated - as discussed in "The Organ Mountain Range, its History and its Orchids" by Miller, Warren et al with the same results.
IN general people either said, "oh we knew that" (lies) or ignored it... I had been asking the question of quite learned foljk for many years as to how orchids get their nutritional needs which are the same as for any other green plant , and never getting any sensible answer... personally I feel I ought to have got a medal or something for all this... (joke ). But there you are. Now you know.

[Dorsetman]

But to go to the other questions, tap water and ground water in general contain a lot of dissolved stuff which is useless for plant growth but contribute to a high EC (Electrical Conductivuty) reading - and if you pile in proper fertiliser to give plants what they need as well, you end up with an EC so high it will scorch the roots. That why rain or Reverse Osmosis water is excellent. Nothing in it to start with ( or very little ) leaving you room to put in what plants want.
And as for pollutants in the water - why not collect a smaple and check it out ? All you need is a pH meter and an EC meter , and personally I don't want to water a p[lant without having those to check what I putting on anyway !,
If it comes out ( your Chicago rain) under 100EC , then its great. I doubt if your tap water is less than 500 . pH is easily put right too.