What Is a Cistern?

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A cistern is an underground tank that captures and stores rainwater that you can use for irrigation, emergencies, or daily water needs. Cisterns are especially helpful in areas with unreliable or expensive municipal water systems. We’ll explore the different types of cisterns, describe the benefits each offers, and explain how cisterns differ from wells in the guide below.

Definition of a Cistern

A cistern is a watertight tank that collects and stores water for later use and is typically made of reinforced concrete, cinder block, precast concrete, fiberglass, and steel. Your home’s gutters and downspouts usually funnel rainwater into your cistern, and you can use that water as a supplemental supply, an emergency supply, or for irrigation. Cisterns can also hold groundwater, household greywater, spring water, well water, or treated city water.

Professionals can install cisterns above ground, underground, or into building structures. Burying cisterns underground might be the best option, though, as underground cisterns keep water cool during warm months and prevent it from freezing during colder weather.

Cisterns intended for domestic use typically hold at least 5,000 gallons, but sizes and setups vary according to homeowners’ needs.

Types of Cisterns

Most cisterns fall into one of three basic categories: rainwater cisterns, water storage cisterns, and greywater reuse cisterns.

Why Have a Cistern?

Cisterns help homeowners tap into additional water sources, reduce their water consumption, and prepare for emergencies.

Emergency Water Supply

Ground cisterns provide backup if disaster strikes or service disruptions affect your primary water supply. Having this water source can be lifesaving if you live in an area prone to flooding or hurricane damage, as you can fill your cistern with city water ahead of potential natural disasters. 

Irrigation Systems

Cisterns make it possible to keep your lawn lush and green without wasting water. You can use your cistern’s rainwater or greywater to water crops and ornamental plants or offer it to livestock. Every drop of water you save is a step toward self-sufficiency and environmental conservation.

Supplemental Water Supply

Many homeowners use cisterns to reduce their dependence on municipal water. Having your own water supply can help you lower your water bills. This is especially advantageous if you live in an area with high water rates or one prone to drought, hurricanes, or service interruptions. 

Fighting Fires

The water stored in your cistern can be a helpful resource for firefighters. This is especially true if you live in a remote area far from ponds or fire hydrants. Quick access to plenty of water can help protect your family and property.

Water Quality

Potential Contaminants

Leaves, debris, and animal droppings can wind up in your rainwater cistern, affecting taste and exposing you to harmful bacteria, such as E. coli. Naturally occurring minerals such as iron and manganese can also affect the taste and color of water, while heavy metals pose a more serious health risk.

Testing and Monitoring

Be sure to test your cistern water for bacteria, heavy metals, and other contaminants at least once a year. Monitor the acidity and hardness of your water to protect your home’s plumbing system. Local water authorities or private labs can provide testing services. 

Treatment Options

You can employ several cistern treatment options to remedy issues or eliminate contaminants. Filtration systems remove sediment and larger particles, while UV lights or bleach can help disinfect the water. A roof washer or flush-first diverter can prevent rooftop debris from reaching the cistern. Consider installing an acid neutralizer, water softener, or reverse osmosis system to address specific water quality concerns. Before considering a water softener system, you’ll want to familiarize yourself with water softener system pricing.

Our Conclusion

Cisterns can keep your garden green, help you to conserve water, and lower your monthly expenses. Rainwater requires treatment to be safe for drinking, but it can be a literal lifesaver during emergencies. 

Cisterns are not a one-size-fits-all solution. Carefully weigh your specific needs and the initial investment against the potential long-term benefits to determine whether installing a cistern makes sense.

FAQ About Cisterns

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