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Food grade barrels are best for use in vegetable gardens.

Ask Gardenerd: Using Rainwater

A great question came into Ask Gardenerd this week:

“Is it safe to use rain barrel water on the organic vegetable garden? My first concern is that the plastic the rain barrels are made of. My second is that we have several of the barrels catching water from the composite roof. What are your thoughts on this? Thank you, Tia”

Yes, you can use rainwater to irrigate your vegetable garden. We’ve been watering with rainwater exclusively since December. Veggie gardens love rainwater, and soil microbes prefer it over chlorinated tap water. There are a few tricks to ensuring safety, though.

Photo by Andrew Cheeseman
Photo by Andrew Cheeseman

First flush

Don’t collect the first flush of rain coming off your roof. It will contain the dust, pollution and other gunk that has settled there since the last rain. In a down pour, wait at least an hour, usually two before diverting the downspout to your rain barrel. Then you’ll have pure water for irrigation at your disposal. The material of your roof shouldn’t be a factor at this point.


Use food-grade plastics for collecting rainwater. Most rain barrels are made from recycled olive shipping containers, so they are safe for use. Avoid using containers that are old and brittle. Those have been photo-degrading and will most likely leach plastic particles into your water. If you have concerns about your rain barrels materials, call the manufacturer to find out what type of plastic they used.


Food grade barrels are best for use in vegetable gardens.
Food grade barrels are best for use in vegetable gardens.


Make sure your rain barrels have a screen in the lid to filter out leaves and prevent mosquitoes from laying eggs in there. Safety first!

Clean it out

It’s important to clean out your rain barrel during the off season. Don’t leave last year’s dregs in there to stew through the dry season. Rain barrels collect sediment that coats the bottom of the barrel. Find a small child to crawl in there (just kidding) and clean it out each year. Then your rain barrels will be ready for the next downpour.

By taking these safety precautions, you’ll have a safe supply of water for your garden for many months. Thanks for writing in, and keep those questions coming.

This Post Has 2 Comments

  1. Hi, I just happened on your site in my search to braid garlic…thanks! I also enjoyed learning about rain water from a composite roof…always wondered about that. Lastly, I’m wondering if you know about clay pot irrigation, with an olla. It is an ancient system that saves up to 70% in water. Not many people write about it, but many people need it. I’ve sited a web,, which is down at the moment for some reason, but is worthy of a look.
    Thanks for the tips!
    Mary Kathryn

    1. Christy

      Thanks for sharing, Mary. We’re fans of Ollas here at Gardenerd. Good luck with your new business.

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