How does rainwater harvesting work?
Water that would normally flow into a roof gutter and down spout is re-directed into a holding tank or rain barrel. A filtration system on top separates debris and leaves from entering the system. During the summer months, the stored water is then used for irrigation.
How much water can I collect?
As much as your system is designed for. Just one inch of rain on a 1,000 square foot roof will yield 550 gallons of water. Your tank or rain barrel will probably be full after the first big storm of the year. Excess water can be directed to a simple rain garden that helps recharge the aquifer.
What is the best use for stored rainwater?
Think of your system as an insurance policy for your outdoor landscaping. Should there be a mandatory restriction on outdoor watering, your rainwater system will see your garden through the dry months (June through September).
Also, plants thrive from rainwater as it is extremely low in dissolved minerals (salts) and has not been treated with fluoride.
How much can a rainwater system hold?
The most popular above-ground tanks options are 200, 300, 550, 1,000, 2,500 and 5,000 gallons. Tanks over 5,000 gallons generally require a concrete pad and possible design review.
| Size | Weight | Width | Height |
|---|---|---|---|
| 200 gallons | 60 lbs. | 36" | 53 " |
| 300 gallons | 80 lbs. | 42 " | 60 " |
| 1,100 gallons | 180 lbs. | 87" | 52" |
| 1,550 gallons | 215 lbs. | 87" | 66" |
| 2,500 gallons | 335 lbs. | 95" | 90" |
| 3,000 gallons | 400 lbs. | 102" | 95" |
| 5,000 gallons | 875 lbs. | 102" | 152" |
Is a pump necessary for a rain harvesting system?
It depends on how the collected water will be used. A pump with 30 psi (pounds per sq. inch) is needed to connect a tank to an irrigation system. A small pump is also necessary to create water pressure for hand watering, particularly if a yard has changes in elevation. That said, a garden hose attached to an elevated rain barrel is capable of delivering water on a level surface.
What roofing materials work best for a rainwater system?
For general irrigation purposes, any roof material is fine. For vegetable gardens and fruit trees, metal, tile and asphalt shingles are all acceptable surfaces for water catchment. Treated wood shingles and older tar/gravel surfaces could have contaminants and are best used for non-edible vegetation. If you have specific concerns, a local soil lab or plumbing company can test your system’s water quality.
What is a first-flush system?
During the dry summer months, dirt, pollen and bird contaminants can accumulate on a roof surface. A first flush system allows debris to flow off the roof with the first rainstorm of the year.
What about tank maintenance?
Before the rainy season, gutters and filters should to be checked and cleaned. They should also be checked after every substantial rain.
Does tank water become dirty?
Standing water in a tank can become old. It’s best if you can place your tank in a shady location. Tanks are made of an opaque material that minimizes bacterial growth. Simple, preventative maintenance will ensure that a rainwater system operates efficiently.
Will I save on water bills?
Yes, having an independent water source will reduce your summer bills - by how much depends on the size of your system and when you use the water. Many water districts have a multi-tier system to determine costs, so using water during the peak months will save money. The real savings could be in the cost to replace landscaping in the event of a drought.
I can only install a small tank, is it worth it?
Yes. Every effort to reduce our impact on the environment is an action worth taking. Of all the energy used in California, water delivery consumes 20% of this total. By keeping water at its point of origin, less energy is required to treat and re-deliver water.