Nancy already had the metal roof, gutters, and 1,200-gallon tank. From there, Innovative Water Solutions opted for a “wet pipe” system that collects water in a similar fashion to a house’s typical drainage system. The downspouts are connected to sealed 4-inch PVC piping, which feed a large underground p-trap located between the house and a cistern. This is common practice when the cistern is located more than a few yards away from the house, so there are not elevated pipes traversing the yard. In contrast, a “dry pipe” system enters the cistern from above without going underground—when it is not raining, the pipes hold no water, negating concerns about harboring mosquitoes. Nancy’s wet pipe system includes a 2-inch pipe at the low point in the collection system that has a faucet with a slow drip to empty the pipe after a day or two of no rain, which reduces insect concerns.
Since her home has two stories, the gutters generally sit well above the tree line, so maintenance for tree debris isn’t a big concern. There’s no need for screens or other covers on the gutter, and her system doesn’t include a rainhead—an open box that separates out leaves and other debris from the rainwater. Eschewing gutter screens and the rain head saved money initially, but meant the frequency of cistern cleanouts likely needs to be increased (something done on a typical rainhead-based system about once a decade).
At the cistern, the pipe comes above ground, stopping at a “first-flush” diverter that siphons off the first 50 gallons or so from each rainfall event and directs it to the surrounding landscaping via a slow-drip irrigation system. Small leaves, bird droppings, dead insects, and other unwanted bacteria-containing debris that have built up on the roof since the previous rainfall come off in this first flush. Keeping it out of the cistern greatly reduces sediment buildup and potential water contamination. The first-flush diverter has a rubber gasket at its bottom with a small hole in it for dripping out the water between rainfall events, as well as a 4-inch cap that unscrews for debris removal.
Keeping light out of the cistern is crucial, or else microorganisms such as algae can flourish. The polyethylene tank exterior is UV-resistant, with an expected life of 30 years or so. This can be extended if the tank is shaded, saving the top from becoming brittle and potentially broken by hail or downed branches. An overflow outlet drains off excess water and an access hatch on top allows periodic cleaning and maintenance. Sunlight heats up the water in the tank in the summertime to upwards of 90°F, but Nancy is able to cool the water by first routing it through her original, shaded 1,200-gallon tank. While hot drinking water coming out of the tap is not ideal, preheated water reduces the energy load for her water heater.
Water is pumped from the main 5,000-gallon cistern to the smaller 1,200-gallon auxiliary tank, activated by a float switch in the auxiliary tank. A screened floating intake valve—reinforced vinyl tubing attached by a short chain to a black-plastic floating ball—pulls water from a few inches below the surface, thus avoiding floating debris and bottom sediment.
From the smaller cistern, a Grundfos MQ3-45 pressure-booster pump with built-in bladder tank provides household water pressure. Before entering the house, the piped rainwater is forced through a two-stage filtration system—a 10-micron sediment filter and a 5-micron carbon filter. Nancy’s water is then purified by an ozone injection system. Once thoroughly mixed with the water, the extra oxygen molecule kills any bacteria and viruses.