Rainwater Collection: a Primer

13 May 2013 No Comment

Rainwater collection is a great way to reduce landscape water use, reduce erosion and recharge our aquifer by letting the water slowly percolate on site. Plants show significant response to the nutrient-laden chloramine-free water. All of the asphalt and concrete in our cities direct runoff water to our creeks and rivers, frequently at damaging rates that lead to floods down stream. Keeping water on-property allows soil life to thrive and ecosytem health to be at its prime. Swales, rain gardens and ponds all perform this function, but tank storage may be the best option for an urban resident. It is no surprise that more and more people are turning to harvesting all that rainwater pouring from their roofs during our unpredictable rainfalls. But where to start?

YardFarm rainwater collection tank installation

The first step is to ensure that you have a method of collecting and directing rainfall – a roof and gutters. Gutters help collect and direct rainwater towards a tank. If you don’t have gutters, you’ll want to consult a gutter company and see to that. Gutters are also good for your foundation and can help keep runoff from being a destructive force in the landscape.

Between your gutters and tank is a first-flush diverter. The first amount of water collected in a rain event can be contaminated with debris and residue from your roof (pollen, dust, droppings), which can gunk up your system and settle in the tank. To avoid this, we install a first-flush diverter, which simply diverts the initial dirty water away from your tank.

Many people are familiar with the small 50-75 gallon rain barrels around town. While 50 gallons may seem like a lot , consider that a 1,000 square foot catchment area (i.e. roof) in a 1 inch rain will shed 600 gallons. This means that your 50 gallon tank will fill up almost instantly in any significant rainfall and the rest will be wasted. Unless you want to chain 12 of these together in a system, it’s probably better to go with a more substantial tank. The other thing to consider is that rainfall in central Texas is sporadic and unreliable, and this factor makes storage even more important. You’ll want to collect and store all you can. Rain tanks can go from a few hundred gallons to thousands – consult with us and we’ll help you choose the right size for you and your family. www.tanksforless.com has a great section of tank styles and sizes including a few that are locally made.

People that utilize only rainwater in their homes absolutely love it and would never go back to chlorinated water. In the shower the feel of the water is preferable, it tastes delicious and the health benefits are numerous. A 3 part filtration system would be necessary for consumption. For whole house use its best to have in the 7000 gal /person vicinity. Average use varies widely, but about 15,000 gal/year per person is average. A decent size vegetable garden would be supported by an 850-1200 gal tank. Always keep in mind the numerous benefits of having clean stored water on your property in the event of a municipal supply failure.

Once you’ve selected a tank, you’ll need to decide where you want the tank. The tank needs to be set on a flat constructed pad at least 6 inches deep. A concrete slab is good, but a base of sand or crushed granite will also work. Tanks do not need to be top-fed so you can place the tank away from your house if you so choose. Once the location is decided and pad built you must plumb the system. This involves running the supply line from the gutters to the tank, as well as an overflow outlet and a municipal feed if necessary.

Now you’ve gathered all this wonderful rainwater, you need a way to utilize it. For smaller tanks, you could make great use of the water by hand watering potted plants and small beds. A drip system or other type of irrigation will most likely need a minimum pressure of 10 psi. To achieve this pressure by gravity you would need 23 feet of vertical drop. Some drip tapes work at 4 psi. You can achieve this pressure with a 9 foot vertical drop (between tank outlet and garden). For those of us that live on flatland though, a pump is necessary. Once set up, the pump will help deliver rain water to your plants and vegetables and leave you time to enjoy your garden and landscape.

Collecting your own rainwater is smart, economical, and environmentally responsible. No more running up your water bill to keep your landscape and vegetables healthy. And here in Texas, water is an increasingly scarce resource (and increasingly expensive), so harvesting your own rainwater helps lessen pressure on our precious water resources. Contact us today to discuss setting up the right system for you. We have designed and installed numerous systems and have received training from the Texas Rainwater Catchment Association.

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