This summer, some homeowners will be swimming in their backyard pools au naturel. The iconic, aqua-blue vessels of chlorine-treated water are starting to see competition from the leafy, greenish waters of natural pools.
As the second summer of the pandemic approaches, waiting lists for in-ground pools and a chlorine shortage are sparking interest in these so-called bio pools, which are chemical-free. Swimmers are invited to lounge, naiad-like, close to water mint and water lilies as dragonflies hover.
“Prices are going through the roof on chlorine tabs—if you can even find them,” says Christopher Paquette of Robin’s Nest, a natural-pool company in Buxton, Maine.
Natural pools are a tiny fraction of the U.S. residential pool market, which is dominated by pools that use chlorine and other chemicals to keep bacteria and microbes at bay. Theyare a sustainable choice, requiring less energy to operate.
The result is green water—somewhere between a mossy hue to a jade color. The roots of aquatic plants, such as water lilies, and materials like gravel create a naturally occurring ecosystem with biofilms called a regeneration zone. Water is kept clean and algae-free as it recirculates over the film of micro-organisms. Newer technology replaces this regeneration zone with a smaller, self-contained, plantless biofilter, which uses material such as lava rock and gravel to build up a biofilm.