Our first-flush diverter is finished. Now all we need is rain.
Our catchment water system takes runoff rainwater from the roof and stores it in a water tank. Pretty cool if you get enough rain (supposedly, we do, but for the last six months we’ve been well below average even though it’s been “rainy season”) and you can make sure the water is fit-for-purpose. In our case, we’re only going to use it for laundry and for backup to our municipal water supply. In the latter case, we would run it through a specialized disinfecting and filtering system before actually drinking it.
When it doesn’t rain, though, dust and dirt and fallen leaves accumulate on the roof, along with less savory things such as bird, rodent, and arthropod excrement and precipitated particulate air pollutants. Most of that washes off the roof early in a rainfall, so most catchment systems employ a first-flush diverter which is just a large, capped downspout. It fills up with the icky first rainfall and, only after it is full, does the overflow water go into the tank. It isn’t perfect, but it gets rid of the worst of the contamination. One need only remember to drain the diverter after each storm.
—2p