Oh - I know that a very popular fertilizer put out by MI State U has two formulas, one for tap water & the other for rain/distilled/RO water, so there are SOME considerations, but nothing particularly significant.

Most rain water, but not all, will be slightly acidic - usually a good thing, and it will have some sulfur in it - sometimes some Ca. I have about 20 little houseplants and a few larger ones at work that are all watered with distilled water - roughly equal to your rain water. I add a few drops of FP 9-3-6 to a quart of water and use that every time I water, and it's been keeping them all pretty happy for 11 years +. If I had my choice between rain and a municipal water supply for my plants, it would be rain every time - hands down.

Al

I have a large water butt full of tapwater, but I worry since it's not being aerated by an air pump. Surely an environment with low dissolved oxygen levels is hospitable for some pathogens such as pythium?

I've started using a product from my local DIY/garden centre made for water butts that contains enzymes and supposedly prevents the water from going green or scum.

I'd love to use the water but it just seems risky. I was thinking of buying a small 9W UV pond clarifier to sterilize the water. In the meantime I might just use my hydrogen peroxide to kill of any pathogens, since the water's been sitting there for ages.

I think it all depends on whether or not the tap water is softened or comes from a municipal source where chemicals are used for purification or added for supposed health.

I would think it better to use rain water than softened water or water that comes from a city source.

Water pumped from a private well that isn't softened would be just ground filtered rain water.

As long as we leach our containerized plants to rid the medium of accumulated salts and minerals when needed, I don't suppose it makes too much difference what the water source is.

I use well water that isn't softened.

Thanks for the info everyone. I had thought rain to be slightly acidic. I heard that most of our native plants prefer acidic soil because of our rain amounts, normally 100+inches per year. We're in a wierd geographical spot I guess. Two weeks ago we got 8inches while everyone around us, even as close as 20 miles got around 3 or 4. And this happens alot.
My water comes from a well, as most do in my area. I don't trust it though unless it's boiled, because home tests I've done show alot of bacteria. And I live in a low, swampy area and everyone has septic problems. I figured if I won't drink it, I don't wanna eat vege's watered with it.

Hi Sam!

For my plants, ALL THE DIFFERENCE IN THE WORLD... That is an understatement.

My water carries salt despots, fluoride,chlorine, and the pH is very high.

In my case, if I use faucet water on my plants, the pH is too high, and the deposits from my water can stunt growth along with cause brown tip on many sensitive trees and plants. My gardenias, ferns, palms, peace lilies, and philodendrons in particular react poorly over time with faucet water.
That is why I will use distilled water if I can, or use rain water and fill 30 gallons buckets to hold me through the winter.
I had just enough rain water left over the long winter by sacrificing some of my not so important plants to faucet water, and this is the result.

Notice the tips on the first two pictures of what other wise is a very green plant until I stop using rain water. This is growth over the winter with faucet water. Even worst if you use a bagged mix.

Incredible difference with rain water as the new growth and growth since I switched to rain water is now coming and staying green to the very tips.

Mike

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With RIAN WATER..:-)

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Not only do I love to water and fertigate with rainwater....I also love to wash plants in the rain!
The lack of residue is such a bonus!

Josh

I use well water from two wells. Both are full of minerals from the soil which makes them plug up the drip system as the minerals are in solution and cannot be screened out. On the well used for irrigation I use a diatomaceous earth self cleaning filter to remove some of the mineral. For the drinking water for the house I use a 2500 gallon tank with an ozone generator and filter which precipitates out iron and manganese and makes the water palatable. All of the water I am sure was at one time rain water, but after a stay in the soil is is nothing like rain water. Al

You know... if you're not sure you'll have enough rain water, snow can be melted and brought to room temperature... if you have access to snow over winter, that is. Just a thought for those who collect rain water and prefer to use it.

This Season, I have inserted a filter in the head-end of my drip irrigation system:

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After researching RV filters and other options, the only one that is effective vs. Chloramine in our municipal water system is one made of KDF / GAC. Should last me through the growing Season. About $20.00 on Amazon.com.

Raybo

I normally just use reverse osmosis (RO) water. I think it's more important to use rain water/RO water on plants like Blueberries since they need acid conditions at the rootzone.