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Water Harvesting: Rain Barrels and Cisterns

Rain barrels and cisterns collect and temporarily store rainwater from roofs. This water can be used to water gardens, lawns, and trees. Rainwater enters them from gutters and downspouts and there is an outlet that can be connected to a garden hose. When they overflow, excess water is directed away from the building to a location on the property where it can soak into the ground. 


Why Should I Install a Rain Barrel or Cistern?

Image of a rain barrel with plant growing on top.
Rain barrels come in different designs and shapes. These rain barrels have plants growing on top. 


By collecting your roof runoff in rain barrels or cisterns, you can reduce polluted stormwater runoff from your property. Stormwater runoff is reduced, because you are collecting the stormwater and allowing it to soak into the ground when you use it for irrigation.

When you use the rainwater to water your gardens and landscaping, you also use less potable (tap) water for this purpose, which can lower your water bills. Since rain barrels and cisterns collect rainwater for use on site, they can reduce the harmful effects to streams caused by large and rapid stormwater runoff flows.


What is the Difference Between a Rain Barrel and Cistern?

Rain barrels come in a variety of sizes but typically as a 55-gallon container that collects roof runoff. Rain barrels can be added to any building with gutters and downspouts. All rain barrels require an overflow port. Rain barrels are usually around the size of a trash can, but cisterns can be much larger, ranging from the size of a washing machine to a car, to collect and store more water.

To be eligible for a RainScapes Rewards Rebate, the total rain barrel capacity on your property must be at least 200 gallons.


Cisterns are sealed tanks that can be located above ground, partially buried, or below ground. Cisterns are larger than rain barrels and they can collect water from several downspouts from one building’s roof or from multiple roofs if they are large enough. Large cisterns may require a permit, so please check with the County’s Department of Permitting Services. When cisterns or rain barrels are full, the overflow should be directed to a safe location away from the building foundation. Overflow may also connect into a dry well, rain garden, or other area where the runoff can infiltrate into the ground on your property.  To be eligible for a RainScapes Rewards Rebate, a cistern must be a above ground stand-alone system for landscape applications and non-domestic use, and there must be sufficient space on your lot to accomodate overflow.

To avoid mosquitoes, rain barrels and cisterns should be emptied within 1 week of a rain event. 

Water collected in rain barrels or cisterns is for non-potable, exterior uses only; the County does not currently permit hooking these devices into your home’s sewer system for actions such as toilet flushing. Cisterns may be connected to existing stormdrain systems, but it is expensive to do so and a direct connection will require a permit. 

Cisterns may require an electric pump to empty out the water, which may require a permit from the County’s County’s Department of Permitting Services. Contact Permitting Services to obtain information about the necessary right-of-way and other applicable permits to connect to a public storm drain system.





Is a Rain Barrel or Cistern Right for Me?

Rain barrels and cisterns are often the first stormwater management practice installed on properties, because they are relatively inexpensive, useful for watering gardens and they don't require a lot of space.  They may not be suitable for your property if you do not have access to a downspout, or you do not think you could provide regular maintenance. 

Image of the front of the RainScapes Rain Barrel and Cisterns Guide

Want Help with Assessing Your Property and Installing Rain Barrels or a Cistern? Download the Guide. (PDF, 661KB) 

Rain barrels and cisterns:

  • Reduce the use of potable, treated water for landscaping purposes 

  • Provide a small amount of storage for stormwater runoff from the roof 

  • Are a good option if roof downspouts currently discharge to a driveway or sidewalk 

  • Are relatively easy to install and are inexpensive 

  • Require some maintenance. Rain barrel and cisterns must be emptied 1 week after, or in between, rain events. They must also be winterized by the end of November

  • Are best suited to sites where there is a nearby garden where the water can be routinely used, or the drain spigot should be left open to empty the system 

How to Assess Your Property

Take some time to walk around your property to assess your roof gutter and downspout system. Do this when it is raining, so you can see where the rain lands on your property and where it flows. Follow these basic steps to identify your property’s drainage conditions:

  1. Locate each downspout.

  2. See where rainwater from each downspout flows. You may find that your downspouts are directed to your grassy lawn, a landscaped area, a storm drain, or your driveway. If rainwater from a downspout currently flows to a grassy or landscaped area, you may not need a rain barrel because water is already soaking back into the ground. The best place for a rain barrel is where downspouts discharge onto or near a hard surface, such as a driveway, sidewalk, or patio, where the water cannot be absorbed.

  3. Once you have identified downspouts for a rain barrel or cistern, you need to estimate the size of the roof area that contributes water to each downspout (see diagram below). Based on your observations in Step 2 of where the rainwater flows, estimate the drainage area (square feet) to the particular downspout. Web maps such as Google can be used to measure your roof areas (using the measuring tool) if you don’t have a site plan of your lot. You can also measure the length and width of the roof from the ground with a tape measure. We do not recommend climbing onto your roof to measure its area. Then estimate what percentage of the building’s total roof area this amount represents. The drainage area and percentage of the building’s roof area are required for the RainScapes Rewards Rebate application. 

Image of house with explanation of how to calculate the drainage downspout area


Image of people installing a rain barrel.Installing Your Rain Barrel or Cistern

Ready to move ahead with installing rain barrels or a cistern?  

Many rain barrels can be installed without a contractor.  If you would like to hire a contractor, download the Rain Barrel and Cistern Guide (below) for helpful questions to ask and other information. 

There are a lot of decisions that need to be made with your rain barrel and cistern after the assessment is complete.

  • Sizing the rain barrel or cistern

  • Finding the best location

  • Developing a maintenance plan

  • Design of the rain barrel.  Do you want to get creative with your rain barrel or cistern?

  • Whether you want to do the project yourself

The RainScapes Rain Barrel and Cistern Guide (below) has suggestions and useful information on how to best make the necessary decisions.  The RainScapes program has knowledgeable and helpful staff who can help you through the process as well as the RainScapes Rewards Rebates program with great financial incentives for installing the rain barrels or cisterns.  


Download the RainScapes Rain Barrel and Cistern Guide (PDF, 661KB)


Watch a Video from a Rain Barrel Make-and-Take Workshop




Maintaining Rain Barrels and Cisterns

Image of the front of the Rain Barrel Maintenance Fact Sheet.

Want Help with Maintenance, Troubleshooting and Timelines?  Download the Fact Sheet.  (PDF, 335KB)

Rain barrels and cisterns require maintenance to keep them healthy, functional and to prevent problems, such as mosquitoes and flooding. You can prolong the life of your rain barrel and save money on maintenance costs by regularly inspecting and maintaining the rain barrel to ensure it is functioning properly. Unmaintained rain barrels and cisterns may:
  • Overflow and cause erosion near the foundation

  • Become clogged and not allow rainwater to pass into or out of the rain barrel

  • Become a breeding place for insects or tip over

  • Cause ice dams in the winter if not disconnected

By maintaining your practice, you are doing your part to help the environment and protect  your local streams and the Chesapeake Bay.  




Actions You Can Take to Maintain Your Rain Barrel
As Needed Seasonally

✔ Check the entire system (e.g., gutters, debris filter, overflow pipe, fittings, spigot, etc.) to ensure the barrel is functioning properly

✔ Unless the rain barrel is made of a material specifically designed for freezing temperatures, disconnect it during the winter to avoid damage. Around Thanksgiving, disconnect the rain barrel from your downspouts, empty the barrel, wash out the barrel, and store it upside down in a protected location. Connect the barrel to your downspout around April Fool’s Day.
✔  Place gutter guards and/or screens on top of roof downspouts and on top of the barrel to prevent leaves and sediment from entering the rain barrel. ✔ Open the rain barrel spigot if you expect to be away from your home for an extended period of time; make sure it will drain away from your foundation.
✔  Remove leaves and other debris from the screen at the top of the barrel, the overflow pipe, and the roof gutters. ✔ Clean the barrel using a non-toxic substance such as vinegar to remove residue or algae.
✔ Regularly use water collected in your rain barrel between rain events to make sure there is room to collect rainwater during the next storm. Drain your rain barrel before the winter season. ✔  Clean out downspouts and roof gutters for the most effective mosquito control. However, if you find mosquitoes in your rain barrel, you may use dunks. A quarter dunk added monthly may be adequate for a 55-gallon rain barrel.
✔ If your barrel has a filter screen, make sure it is intact without holes and securely fastened to keep out mosquitoes.  


Actions You Shouldn't Take to Maintain Your Rain Barrel
✘ Don’t leave water in your rain barrel for long periods of time.
✘ Don’t drink the water in your rain barrel or use the water inside your home or for your pets. This water should only be used as non-potable water.
✘ Don’t let kids play in or around rain barrels.
✘ Don’t forget to reconnect your rain barrel every year after the winter frost season.
✘ Don’t spray the water directly on vegetables or leaves, as it may contain bacteria from the roof.
✘ Don’t let the barrel foundation become unlevel or unstable. A full 55-gallon barrel weighs 450 pounds and can tip over on an unstable surface.


DEP can answer your questions and provide additional guidance about maintaining your rain barrel or cistern. Please email, call the Montgomery County Customer Service Center at 3-1-1.


Rain Barrels and Cisterns in the Stormwater Facilities Maintenance Program

The Stormwater Facilities Maintenance Program is responsible for maintaining all public stormwater facilities as well as all private facilities that transfered their maintenance to the County.  The program also maintains facilities that were required as part of the Department of Planning permits.

Not sure if your rain barrel or cistern is part of the Stormwater Facilities Maintenance Program.  Check out online Facilities Map or email


Can I remove my rain barrel or cistern after installation?

No, you cannot remove any facilities that were part of your building installation - these are permitted structures and DEP maintains a database of these facility locations as part of the Stormwater Facility Maintenance Program. DEP may perform a maintenance inspection of your practice if it is a permitted structure.  Rain barrels and cisterns that are part of the Stormwater Facility Maintenance Program must contact DEP before any major changes can be performed to the structure. 


Rebates, Resources and Financial Incentives

Interested in installing rain barrels or a cistern?  The County offers incentives to help make the decision a little easier.


Logo of the RainScapes programThe RainScapes Rebates Program

The County offers technical and financial assistance (in the form of rebates) to encourage property owners to implement RainScapes techniques on their property, including rain barrels and cisterns.

  • Residential properties are eligible for up to a $2,500 rebate

  • Commercial, multi-family or institutional properties are eligible for up to a $10,000 rebates.

To participate, your property must be located in Montgomery County,outside of the municipal limits of the City of Rockville, City of Takoma Park, or City of Gaithersburg. Projects are not eligible if they are associated with permit approval requirements for new building construction, additions, or renovations.

​The program is funded each fiscal year (The FY begins July 1 and ends June 30). Annual funds for the programs are limited, so rebates will be awarded on a first-come-first-served basis.

The RainScapes program also provides technical assistance to help with the installation of your rain barrels and cisterns.  They have a wealth of information, expertise and want to help!

Learn more on the RainScape Rewards Rebates webpage.


Image of a group of people with rain barrels

The Water Quality Protection Charge Credit Program

After you have installed your rain barrel or cistern, you are now eligible to receive a credit off your annual Water Quality Protection Charge (found on your yearly property tax bill).  The credit provides an incentive for maintaining your rain barrel and other stormwater management practices.  

You must apply for the WQPC credit separately – the credit will not be provided to you automatically.

Residential property owners can receive up to 50% off their WQPC depending on the type and size of stormwater management practices on the property. 

Non-residential and multi-family properties can receive up to 50-60% off their WQPC depending on the type and size of the stormwater management practices on the property. 

Cisterns provide a large credit, while rain barrels provide the smallest credit of any stormwater facility practice.  The low credit is because rain barrels divert the least amount of stormwater of any practice. 

Learn more on the WQPC Credit webpage.