How to determine if water from rain barrel is safe in garden
July 13, 2010 9:29 AM   Subscribe

I'm looking for information regarding the safety of using water from a rain barrel in a vegetable garden. Has anyone seen any studies that test water from a rain barrel to determine its quality? How would I go about getting water tested to make sure it's safe?
posted by GernBlandston to Home & Garden (14 answers total) 4 users marked this as a favorite
Safe for drinking, or for watering your plants? I don't have a study, but I know many many people who irrigate with water from a rain barrel. Unless it's been stagnant for years, it is just rain after all.
posted by Think_Long at 9:33 AM on July 13, 2010

We've been using the water from our rain barrel for a few years in the veg garden- we've not had any problems. This might help.
posted by palacewalls at 9:37 AM on July 13, 2010

Not all rain is the same. In a region with serious air pollution you can get acid rain. If the rain is acidic, that affects the pH of the soil. Different types of plants have their own different pH requirements. If you are growing the kind of plants that do well in acidic soil, then acid rain will be good for them, and will act as a kind of fertilizer. If they require alkaline soil, then you can correct the soil pH by adding lime. In either case you can use the rain water even if it is acid rain. But if you are not measuring the acidity of either the rain or the soil, and do not know the specific requirements of your plants, you have no way to judge the situation other than to see how well the plants are growing (which can be affected by various other factors).
posted by grizzled at 9:45 AM on July 13, 2010

I'm having trouble understanding what you think might be the issues with rainwater? too acidic? pollutants from your roofing material? What? Generally, rainwater is 'softer' than tap water, it has fewer minerals, and is nearly always considered beneficial for plants. Unless you've got a toxic dump for your roof, the water collected from it should be no more harmful to your plants than when it falls out of the sky onto them.
posted by dbmcd at 9:48 AM on July 13, 2010 [1 favorite]

What are you thinking might be happening to the rain in the rain barrel that would make it different from what it would be if it just fell straight from the onto the plants?
posted by ThatCanadianGirl at 9:49 AM on July 13, 2010 [3 favorites]

I'm not especially careful about what I eat but frankly for an application like that I would stick to untreated wood barrels, FDA-approved food-grade plastic barrels, or virgin steel barrels (maybe). The recent bisphenol scare was a good illustration about how cross-contamination can occur, and growing plants will pick up a lot of different chemicals in its root system. I wouldn't go by any reports of no problems, as carcinogens are long term issues and it's like deciding whether to smoke by asking smokers you know whether they have any cancer.
posted by crapmatic at 9:50 AM on July 13, 2010

uh.. straight from the sky onto the plants?
posted by ThatCanadianGirl at 9:50 AM on July 13, 2010

Here is a press repease about just such a study being done at Butler University, starting last December. It might be worth emailing Professor Olujide Akinbo to see if anything has come of it.
posted by ChrisHartley at 9:59 AM on July 13, 2010

Be sure you're collecting it in a proper rain barrel. A lot of people will set out any old container and call it a "rain barrel."

A proper rain barrel has mesh and a lid which will exclude insects, bird droppings, mosquitos looking to lay eggs, etc.

I knew someone who used a big 50-gallon drum as a rain barrel one year. He drank from it, too, thinking that it was pure water having fallen directly from the sky.

Problem being, once he got down to the bottom, he found the remains of a bird which had fallen in and drowned.
posted by ErikaB at 10:04 AM on July 13, 2010

No studies but the concern with rain water collected from roofs is from what is on the roof. Namely what the roof is made of and what particulate matter has accumulated on the roof.

For the former asphalt shingles are less than ideal; metal, slate, wood or glass is better.

For the latter the contaminate load is going to depend on your local air quality and also how much and how often it rains.

Both issues can be mitigated somewhat by discarding the initial wetting and washing water, called first flush, from your roof. Many designs are available both commercial and diy to handle the automatic diversion of this contaminated water.
posted by Mitheral at 10:07 AM on July 13, 2010

I've been watering food plants with water from a rain water butt that gathered water from the roof for years. I'm still here. I have the usual amount of heads. Unless you live somewhere where the rain has to fall through smog of some kind, you should be safe.
posted by Solomon at 10:34 AM on July 13, 2010

Also, you're going to get a lot of chemicals in and on the food you eat, unless you buy organic.
posted by Solomon at 10:35 AM on July 13, 2010

Rainwater is better for plants than tapwater. Or at least, it is according to every single gardening book and magazine I've read (which is a lot).
posted by idiomatika at 12:33 PM on July 13, 2010

All the comments talking about concern about collected rain water are referring to drinking it directly.
There is no mechanism by which it could be harmful to you via your plants.
Consider that commercial farmers use chemicals including copper sulphate, ammonium nitrate and god knows what else. The tiny concentration of something from your roof or leached from a barrel is minuscule.
posted by bystander at 11:53 PM on July 13, 2010

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