Municipal water costs are rising, and in many areas of the country the municipal water supply is under strain. Systematically collecting rainwater for home use can help take pressure off the municipal water supply and also reduce homeowners' monthly water bills.
The most common way to collect rainwater is to "catch" water that falls on the home's roof and direct it, usually via gutters and downspouts, into a rain barrel or a cistern for later use. For every inch of rain that falls on a catchment area of 1,000 square feet, you can collect about 600 gallons of rainwater. For example, a home with outside dimensions of 27 x 37 feet with overhanging eaves of 1.5 feet at each wall has a total catchment area of 1,200 square feet [(27 + 3) x (37 + 3) = 1,200]; for every inch of rain that falls on this roof, 720 gallons of water [(1,200 ÷ 1,000) x 600 = 720] of water can potentially be collected. Note that rainwater catchment systems typically are 70 percent to 90 percent efficient; all systems lose some of the water because of spillage, wind, evaporation or other reasons.
A common and easy-to-implement use for collected rainwater is watering outdoor landscaping. Rainwater is naturally good for plants. It doesn't contain the minerals, chlorine, fluoride and other chemicals that municipal water does, and it can be used directly from the rain barrel or cistern without special filtering. The simplest way to collect rain for landscape watering is to put a rain barrel under one of the home's downspouts. A variety of barrel types and sizes are readily available for home use, ranging from 55 to 80 gallons. To collect more water, connect several rain barrels together near the bottom with PVC pipes or hose. The water can be used directly from the barrels via a spigot or hose, or install a small pump in one of the barrels to pump water to the landscape. Greater amounts of water can be collected by using gravity to carry water from all the home's gutters to a larger cistern for longer-term storage. These systems almost always involve a water-treatment system and pumping the water back to the landscaping.
Collected rainwater can also be used for drinking, but it requires special filtration. The simplest and least expensive type is a microfiltration process that uses gravel, sand and charcoal. More expensive treatments include UV sterilization and ozonation. If rainwater is going to be collected for filtration and drinking, it's important to understand that many areas require that the filtration system be certified and that the water be tested regularly.
Health and Safety Considerations
When using the home's roof as the rainwater catchment area, select the roofing materials carefully. Stainless steel and galvanized steel with a baked-on enamel, lead-free finish are the best because they’re smooth, impervious and not treated with chemicals that will leach into the water. Poor choices include organic roofing materials such as wood shakes, clay tiles and concrete materials, because they'll support algae and mold growth, and wood shakes treated with preservatives can contaminate the water. Other poor choices include asphalt shingles, rolled roofing and porous or rough materials, because they'll hold more particulates such as bird droppings and heavy metals. Porous materials also absorb more rainwater, reducing the collection efficiency.
In addition to roofing materials, consider the materials used for the gutters, downspouts and piping. Avoid using lead-based solder in all metal-to-metal connections. Opt for piping made of roll or channel-formed copper, aluminum, stainless steel, galvanized steel or PVC to limit water contamination.
Follow these additional guidelines for safe collection of rainwater:
- Check with the local government about possible environmental contamination. If the home is in an area that produces heavy industrial pollution, the rainwater may be contaminated.
- Locate rain barrels on level, stable ground. At maximum capacity, rain barrels will weigh quite a bit and will tip more easily on uneven ground.
- Cover barrel openings. A tight-fitting lid will keep children and small animals from drowning. It also will stop algae from growing, minimize accumulation of leaves and other contaminants and prevent the barrels from becoming mosquito-breeding grounds.
- Use an overflow device. Make sure the collection system has an overflow device to direct excess water away from the home's foundation when the rain barrels or cistern reach capacity. An overflow device can consist of something as simple as allowing excess water to continue through the downspouts into the municipal storm sewer.
- Monitor water collection. Check rain barrels regularly to make sure intakes and overflows aren't blocked with leaves or other debris that could limit collection or delivery.