The basic idea of a cistern water system, which collects and stores water in or near a home, goes back centuries. In some parts of Western Asia, archeologists discovered lime plaster cisterns in the floors of houses that were at least 5,000 years old. Ancient Romans also used cisterns beneath their houses to catch, filter and store rainwater.

A cistern is a closed tank, somewhat like a septic tank, but the similarities end there. Instead of sewage, it collects rainwater for household use or irrigation. A home with a well might have a large tank to store water to prevent the well pump from having to work all the time. In some cases, you could consider that tank a cistern, but according to longtime plumber Danny Pen, most cisterns are buried.

Here, we’ll describe a cistern water system and discuss the pros and cons.

What Is a Cistern?

A cistern is a container for collecting and storing water. It can be large or small, underground or above ground, and it’s usually supplied by a spring or rainwater. Sometimes the water comes from a well, but a cistern isn’t a well, because its walls are completely waterproof, which isn’t the case with wells.

Cisterns are often used for irrigation, but a properly equipped cistern water system can also supply household water, provided the source is clean and uncontaminated. That isn’t typically the case with rainwater, but it might be if the water comes from a well.

How Does a Cistern Water System Work?

Cistern water systems for domestic use work like this: Water from an outside source collects in the cistern before being piped into the household water system. This transfer can happen through gravity alone if the cistern sits higher than the main water inlet, but this isn’t usually the case. You often need to pressurize the water with a pressure pump and pressure tank.

Here’s an explanation of the parts of a modern cistern water system:

  • Water source: Cisterns can be fed by wells, rainwater (usually collected from roofs), springs and other sources. It can also be delivered by certified water hauling vehicles.
  • Fill port: This is where fresh water is added to the cistern. Fill ports often come with screens and other filtering mechanisms to prevent debris and contaminants from entering the water.
  • Storage reservoir: Technically, this component is the cistern itself. It’s a watertight container connected by pipes to the water source and your home’s water system. The size and location depend on the water source and your family’s daily needs. On average, a family of three uses about 200 gallons of water daily. It’s a good idea to size your cistern to hold multiple days’ worth of water at a time. According to PennState Extension, the minimum size for a domestic rainwater cistern is 5,000 gallons.
  • Reservoir hatch: All cisterns need a lockable access hatch for cleaning and water inspection. It needs to be watertight to prevent contaminants from mixing with the water inside. A water tank without this hatch is just a tank—not a cistern.
  • Water pump: If your storage reservoir is lower than the main water inlet to the house, you’ll need a pump to push the water into household pipes.
  • Withdrawal pipe: This connects your storage reservoir to your home’s water system. It should be installed several inches above the bottom of the cistern tank to prevent sediment from entering water pipes in your home.

Cistern Water System Pros and Cons

If you’re considering a cistern water system, it’s important to understand the main advantages and disadvantages to make an informed decision.

Pros

“No chlorine, no fluoride in your water, no surprise boil notices — valuable for people with sensitivities,” says Pen. “If groundwater levels drop or the well starts to fail, having a cistern means you can switch to rain collection or trucked-in water without facing the high cost of drilling a new well.” Here are some other benefits of a cistern water system:

  • More efficient and effective use of weak, low-yielding wells and springs;
  • The ability to store formerly uncollectible water, like rainwater for use during drought;
  • Gravity-fed cistern water systems don’t depend on electricity, so water keeps flowing during power outages;
  • Cistern systems make it easier to avoid groundwater contaminants.

Cons

According to Pen, not all cisterns are set up for drinking water — some are used only for toilets or irrigation. If you want to use that water for showers, cooking, or drinking, you’ll likely need to install filters, a UV system, or other treatment, “and that can get pricey fast.” Moreover, because most cisterns are buried, small leaks or system issues are easy to miss. “Mosquitoes, algae, or mildew are preventable but common problems with cistern water systems.” Here are some other drawbacks:

  • A cistern water system is difficult and costly to install. The larger your family, the more water you’ll need, and the higher the cost.
  • You need to conduct regular inspections, cleaning and testing to ensure the water stays safe and drinkable.
  • A cistern water system is more complex than city water or well systems, providing more opportunities for things to go wrong.

Cistern Water System vs. a Well

The main difference between a cistern water system and a well is that a cistern stores water from an external source, and a well itself is a water source.

A cistern can make a low-yielding well more useful. But cistern water systems are more troublesome, harder to set up and maintain and more expensive in the long and short term.

Cistern Water System Cost and Installation

Cistern water systems vary in cost. How much you spend depends mainly on how large a reservoir tank you need. Other factors include installation fees, pump and pipe requirements and filtration systems.

For cistern tanks with enough capacity to supply residential water systems, expect to pay from $3,000 to $10,000, not including installation fees. Smaller cisterns for irrigation only are much cheaper. A 200-gallon model might only cost $150 to $300.

Pipes, filters and other materials will likely cost about $1,000 for a system large enough to supply an average family’s household water. Installation could easily cost another $1,000 or more, depending on the cistern location (above vs. below ground), the length of pipe to be buried, etc.

For most homeowners, attempting to DIY cistern water system installation probably isn’t wise. It’s a big, complex job requiring considerable specialized knowledge and equipment.

Cistern Water System Maintenance

“With buried cisterns, problems like leaks, contamination, or a broken component can go unnoticed until the system fails — and by then, repairs usually mean digging up the whole thing,” says Pen. “When your entire home depends on that water, regular maintenance is your best way to prevent expensive, messy repairs, and keep water safe.”

To keep your cistern water system working properly and safely, follow these maintenance procedures:

  • Test the water for bacteria and contaminants four times a year.
  • Empty your cistern every year or two for cleaning. It’s best to call a professional if this requires a person getting inside it for cleaning.
  • Disinfect your cistern after each cleaning with a solution of unscented 5.25 percent bleach for every 1,000 gallons of water. Run all water lines until the bleach-filled water comes out. Let the solution sit for at least 12 hours, then flush out and refill the system. Be sure to stock lots of bottled water for the 12-hour interim.
  • Inspect all filters and screens at water inlets/outlets, cleaning and changing as needed.

FAQ

Is cistern water safe to drink?

According to Pen, to be safe for drinking, your cistern must have the following:

  • a food-grade tank;
  • screened inlets and vents;
  • a pre-filter for debris;
  • a sediment or carbon filter;
  • a disinfection step, ideally a UV purifier.

“Even with all that,” he says, “the water should be tested at least quarterly for bacteria and other contaminants. If the system was used for irrigation or toilet water, it likely lacks safe materials and filtration — you’ll need proper filters, UV treatment, and possibly new pipes or tank lining to make it drinkable.”

How do I prevent mosquito breeding in a cistern?

A cistern contains standing water, and that’s exactly where mosquitoes like to breed, so the cistern lid needs to remain tightly sealed. Even then, mosquitoes might still be able to get in, so to prevent that, Pen recommends installing fine mesh screens (at least 1/16″) on every opening, especially the overflow pipe and vent.

“If you already have larvae in your cistern, use a treatment like a BTI-based mosquito larvicide that is labeled safe for drinking water,” he advises.

About the Expert

  • Danny Pen has over 12 years of experience in plumbing, heating, and cooling. He currently leads New Era Plumbing & HVAC, a Massachusetts company specializing in inspection, repair, and replacement services.

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Robert Maxwell
Robert Maxwell is a seasoned carpenter, builder, cabinetmaker, homesteader, stone mason and mechanic. He's been sharing his knowledge through digital and print articles since 2010. Robert lives in a self-built cabin in the woods in Northern Ontario, Canada with his wife and daughter.
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Robert Maxwell