Is a Rainwater Cistern Right for You?
These extra-large containers reduce runoff and save on the use of potable water for the landscape
It’s a win for everyone, because you can save money on your water bill and also allow water to infiltrate your property instead of heading offsite through storm drains. Read on to learn more about rainwater catchment systems and decide if you’re ready to take the plunge.
Because of their size, cisterns are more of an undertaking than rain barrels and benefit from professional advice and help with installation. Everyone can install a rain barrel. They take up very little space and are quite affordable. The barrels are always placed above ground, while a cistern can go above or below.
- Cisterns store more water for longer periods
- Potential to add additional cisterns later if space and budget allow
- Potentially eliminate the use of potable water irrigation for your entire landscape
- Can be integrated with greywater reuse systems to reduce your home’s overall water use
- Can be installed underground or above ground
- Require a large amount of space
- Large initial investment
- Require professional installation help because of their size
- Cisterns over 5,000 gallons in capacity also need structural support at their base
- Prohibited in Colorado; instead you can redirect roof rainwater to a rain garden for infiltration
Large-scale, high-end cisterns are usually used for offsetting the amount of potable water used inside the home and for the landscape and need to be designed in consultation with an architect and engineer.
An underground cistern requires excavation, which also adds to the cost. Underground cisterns are designed on a case-by-case basis and in consultation with an engineer and landscape architect.
Sizing a cistern can be done with a rainwater harvesting tool, like this one from Texas A&M University. Have someone double-check your calculations, and talk with the company selling you the cistern; it will likely confirm the calculations for you.
You can also hire a design professional or green building professional to help you choose the cistern that’s best for you. Among the types of professionals who can help: master plumbers, green builders, LEED-certified professionals, landscape architects and building architects. Look for professionals who specialize in green, sustainable building and design.
- Water holding tank (cistern): Collects and stores the rainwater for later use
- Cover or lid: Keeps tank airtight, but can be removed for maintenance
- Leaf and mosquito screen: Placed at the water inlet to keep leaves and bugs out of the tank
- Overflow mechanism: Allows water to overflow through a directed pipe; consider sending your overflow to a rain garden
Popular materials for cisterns include:
- Concrete: Can be pre-cast or cast in place; a major advantage is that concrete reduces the water’s acidity over time
- Metal: Strong and lightweight; needs to be galvanized and contain a plastic liner
- Polyethylene: Most affordable and most readily available cistern material; not particularly attractive
- Plastic: Affordable but has only a 25-year life span in most cases
- Wood (with a plastic liner): More aesthetically pleasing but also more expensive and not as readily available
- Check with your local building code on setbacks and regulations. A cistern will probably be treated as a “landscape structure” and may require a permit.
- The most cost-effective location will be closest to the source point for the water to be stored — for example, next to a downspout that collects roof runoff.
- It’s easiest to place the cistern uphill from where the water will be used. This eliminates the need for pumping the water, allowing gravity to do the work for you.
Show us: Have you incorporated a cistern into your landscape? Upload pictures in the Comments.