Flushing Your Toilet with Rainwater

With so much rain and so many eco-savvy homeowners, Michigan is a prime place for rain water harvesting in the Midwest. When you also consider that a half-inch of rain collected from just a 300 square foot section of roof will fill a 55 gallon rain barrel, it's easy to understand why every household should have 10+ rain barrels, or find a new way to use the water. So how about flushing a toilet with it?

It just so happens that there exists a practical how-to guide on this exact subject. This is a DIY project, but this guide takes it step by step, explains the very low costs and makes flushing with rainwater seem like a very natural thing to want to do. Here are a few highlights from this Rain Barrel to Toilet Installation Guide:

A few years ago, I bought a 90 gallon rain barrel and hooked it up to my rain gutter on the far side of my house. I used it once in a while, but found it time consuming to fill watering cans and so it went mostly unused. Living near Seattle, I get about 37 inches of rain a year. I often see installed rain barrels around here used for gardens and flowers that are full and overflowing, not living up to their potential. I thought there must be a simpler way to use more harvested rainwater year 'round.

My solution was to relocate my rain barrel on my back porch and then hook it up to my downstairs toilet. This configuration sets the rain barrel about 8 feet above the toilet. When flushed, gravity refills the toilet with rain water from the barrel.
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Rainwater to Toilet Diagram

I did a lot of hunting around on the internet and was unable to find much practical information about doing this on a residential basis. It is my hope that this web page may inspire and help others to hook up a rain barrel to their home black-water (toilet) system.

The City of Seattle is one place that promotes rainwater harvesting for beneficial use and has partnered with organizations like Seattle King County Public Health to develop rainwater harvesting policy and procedures titled, Rainwater Harvesting and Connection to Plumbing Fixtures. The policy provides design guidelines and addresses specific regulatory requirements and procedures for commercial and residential rainwater harvesting systems, including system components.