Home & Garden Home How to Install a DIY Rainwater-Flushing Toilet System (Video) By Sami Grover Sami Grover Twitter Writer University of Hull University of Copenhagen Sami Grover is a writer and self-described “environmental do-gooder,” now advising community organizations. Learn about our editorial process Updated October 11, 2018 glenn-specht / Getty Images Share Twitter Pinterest Email Home DIY Pest Control Natural Cleaning Family Green Living Thrift & Minimalism Sustainable Eating From safe and legal greywater recycling to urban humanure toilets, we've featured plenty of DIY plumbing aimed at more efficient water use. But this DIY rainwater flushing toilet from the UK is about as low-tech and effective as it gets. Using an upstairs balcony to house a barrel cistern; a simple gauze filter system; some charcoal for purification, and then some gravity-fed piping to a downstairs toilet cistern, the system automatically feeds the toilet cistern with rainwater whenever it's available. When rainwater runs out, the homeowners simply switch back to the mains water. Simple, huh?