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Rain Catchment Systems

Rain catchment systems are easy and effective tools for conserving water outdoors. The captured nonpotable rainwater can be used in a number of activities, including watering lawns and plants, as well as washing tools, cars, and pets. Here are some commonly asked questions about rain catchment.

Frequently Asked Questions

What is rain catchment?

Rain catchment via recycled barrels and totes is an easy and effective method for conserving water, especially outdoors. Rain barrels or totes are placed outside of the house to collect rainwater - this water can then be used for nonpotable purposes, such as watering the garden, watering indoor plants, and washing tools, cars, and pets. During a water service outage, the water can be used for flushing toilets.

Why should I use a rain catchment system?

The Board of Water Supply (BWS) estimates that 50 percent of water use occurs outdoors. Because these systems use captured rainwater to irrigate your garden, they reduce the amount of potable (drinking) water used for nonpotable (non-drinking) purposes.

Research shows that up to 600 gallons of water can be collected from just one inch of rain on a 1,000 square foot rooftop. That's enough water to fill 12 large fish tanks! Not only will the use of potable drinking water be reduced when you use a rain catchment system, but the total amount on the water portion of your service bill will be, too.

Is a rain catchment safe for domestic use?

While rainwater catchment systems on individual homes are not regulated by the State of Hawaii Department of Health (DOH), the department encourages homeowners to take appropriate measures to help make the water they collect safe for domestic use. These measures include being proactive with the design, placement, maintenance and testing of their rain barrel catchment system. By taking those steps, homeowners will have greater confidence in their water quality and minimize the need for treatment or corrective action.

Learn more about how to keep your rain barrel water catchment safe for use at your home by visiting the DOH website at http://health.hawaii.gov/sdwb/raincatchment/.

Where can I purchase a rain barrel?

Local vendors often sell rain barrels. You may also check with local companies who use barrels for product storage and see if they have them available. Large trash cans may also be used to construct your catchment system. Please see our video on this page to learn how to construct  trash can catchment.

If we have rain barrels available, there will be a form below which allows you to register for a workshop and then purchase a rain barrel. We do our best to make rain barrels available, but our supply depends on our ability to obtain and process recyclable barrels from local retailers and agencies.

The prices for catchment purchased from the Board of Water Supply (BWS) is $40 for a 55-gallon barrel and $40 for a 55-gallon barrel. Sizes and prices are subject to change.

Can I make my own rain barrel?

Step-by-Step Instructions

Constructing your own rain barrel catchment system can be fun and easy! Check out our video on this page for tips. Step-by-step instructions and FAQs (PDFs) are available via these links for how you can make your own barrel at home. The supply list includes everyday items that may be obtained at your local hardware store.

Rain Barrel DIY Resources
- Barrel Dimensions and Setup Examples
- Construction Instructions and FAQs
- Barrel Placement and Maintenance

Drilling & Threading Services

Do you have a plastic barrel that you want to convert into a rain barrel but need assistance in drilling and threading the hole? Drilling and threading services are being offered to barrel owners by the Master Gardeners at the Pearl City Urban Garden Center. Those interested may call (808) 453-6055 to schedule an appointment for Tuesday or Thursday between 9 a.m. and 10 a.m. or bring your barrel to their Second Saturday event. (Note that pandemic safety measures may have impacted this program.)

Where do I place my rain barrel and how do I maintain it?

Effective placement and routine maintenance of your rain barrel is required to keep it running smoothly and at an optimum level.

Can you connect multiple rain barrels together?

Yes, you can! Homeowners often choose to connect multiple rain barrels together to increase their water storage capacity. Information about how to do this is included in our rain barrel placement and maintenance document.

Where can I go to learn more about catchment systems?


clean water hero logoAdditional information about rain barrels can be found at the City & County of Honolulu, Department of Facility Maintenance, Storm Water Quality Branch’s online Learning Center, including this set of fact sheets: Sustainable Practices for Homeowners.

The University of Hawaii College of Tropical Agriculture and Human Resources (CTAHR) has great resources through their Rainwater Catchment Systems Program.

Prior to the pandemic, the Board of Water Supply (BWS) and the Friends of Halawa Xeriscape Garden (FOHXG) offered quarterly rain barrel workshops at the Halawa Xeriscape Garden, While we currently aren't able to meet in-person, we've made available several other mini-workshops, which can be found here.


Residential Rain Barrel Catchment Rebate
If you purchase a 55-gallon rain barrel from a local retailer, you may qualify for a $40 Water Sensible Rebate!

rain barrel

BWS Recycled Rain Barrel Program

UPDATE: As of 3:00pm on Wednesday, March 6, 2024, registration is closed for the upcoming rain barrel workshop. Mahalo!

The next rain barrel workshop will take place on Saturday, March 16, 2024, from 10am to 11am in Pearl City. For this class, 55-gallon barrels will be available. (Note: Barrels purchased from BWS do not qualify for Water Sensible rebates.)

Please review the catchment information above to learn about other ways of meeting your catchment needs. Mahalo for supporting water conservation! Every drop matters.

Updated: 03/06/2024