It’s important to understand the essential components of a rain harvesting system so you’ll know how the system works as a whole, the parts you need to purchase, and how to maintain it.
The diagram to the left, from the Australian Company, Rain Harvesting, marks each of the components found in a water collection system.
Let me break it down for you and go over each piece of the system. Those components I consider self-explanatory will not include a description:
- Roof or water collection surface
- Gutter screens – keeps out the big debris like leaves and other junk that falls from the trees.
- Rain head – otherwise known as the downspout filter, this component’s main purpose is prevent the gutters from blocking and flooding, but it also adds another level of water filtration. The Leaf Beater is a self-cleaning model that can be purchased for $50 at Rain Harvest Systems.
- First flush diverter – I already covered this item in part 1 of this series, but basically it collects the initial water that runs off the roof, keeping your water free of contamination. The First Flush Downspout Diverter sells for $50 at Rain Harvest Systems.
- Inlet filter or basket strainer – provides an additional level of filtration just before the rainwater enters the tank (sample basket strainer pictured to the right).
- Cistern or collection tank – I covered these in some detail in part 2 of this series.
- Overflow outlet – pretty self-explanatory, if the tank fills entirely the excess water is diverted out of the tank and into the ground.
- Auto-fill / Automatic Top-up Mechanism – this device ensures that your cistern never runs dry. When your water demand exceeds your tanks supply the auto-fill mechanism taps into a water well or the municipal system to keep your toilets flushing, laundry going and plants fed. Think of it as an emergency backup.
- Pressure tank or on-demand pump – this is necessary if gravity alone won’t provide enough pressure to get your water to the various areas in your home where you need it. In a pressure tank system, a pump draws the water from the collection tank, pressurizes it and stores it in the pressure tank until the water is needed. With an on-demand pump there is no need to have a pressure tank since the pump is activated in response to a demand. I should also note that the pump could be located inside the tank as well.
- Water filter – for a potable water collection system, according to the Texas Rainwater Harvesting Manual, “the most popular disinfection array in Texas is two in-line sediment filters – the 5-micron fiber cartridge filter followed by the 3-micron activated charcoal cartridge filter – followed by ultraviolet light.” The 5-micron filter removes suspended particles and dust while the 3-micron filter traps microscopic particles and removes any odors. For non-potable purposes (irrigation, laundry, and toilets) a 15-micron triple action filter would do the trick. The triple action filter removes odors, colors and fine sediments from the water.
- Water level indicator – this can be in the form of a dipstick (floating pole that indicates water level), float or the $100 ultrasonic Rain Alert that has a digital readout notifying you when the water level reaches various levels.
Finally, I should point out that many cities, counties and/or states offer rebates, property tax reductions or sales tax exemptions for purchasing or installing rain harvesting equipment. So do some homework before diving in. Fortunately for me, the state of Texas has several types of offers in and around the Austin area that I’ll be looking into. I’m sure there are other details to consider when installing a rainwater collection system, but this three part series covers enough of the basics to get you headed in the right direction.