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Rain Barrel Water Catchment Systems

The Board of Water Supply (BWS) offers workshops (currently on hold due to coronavirus pandemic) throughout the year at the Halawa Xeriscape Garden where attendees learn about rain barrel water catchment as an alternative and effective method for conserving water outdoors for use in a number of activities including watering lawns or indoor and outdoor plants, as well as washing cars and pets. Here are some commonly asked questions about rain barrel catchment.

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Uwe Ka Lani, Ola Ka Honua - When the Heavens Weep, the Earth Lives (00:07:20)

Using green infrastructure, including setting up a rain catchment system, are ways you can help to capture and use rain water more efficiently and to help keep our water infrastructure, both municipal water and stormwater systems, in good working order.

Residential Rain Barrel Catchment Rebate
If you plan on purchasing a 55-gallon rain barrel catchment system, you may qualify for a $40 Water Sensible Rebate!

Frequently Asked Questions

What is rain barrel water catchment?

Rain barrel water catchment is an alternative and effective method for conserving water outdoors. Rain barrels are placed outside of the house to collect rainwater - this water can then be used for outdoor purposes, such as watering the garden, watering indoor plants, washing cars and pets, and even flushing toilets during a water service outage.

Why should I get a rain barrel 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 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 barrel water catchment system, but the total amount on the water portion of your service bill will be, too.

Is a rain barrel 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/.

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 get a 55-gallon barrel?

Many local vendors sell 55-gallon drums as well as fully-constructed rain barrels online. You may also check with local companies who use 55-gallon barrels for product storage and see if they have them available. Instead of the traditional 55-gallon barrel, large trash cans may also be used to construct your catchment system.

The Board of Water Supply (BWS) does not have barrels available for purchase, except for participants in our rain barrel water catchment workshops (see below). Each household participant is limited to one barrel in an effort to share the product with as many as we can.

Where can I go to learn more about catchment systems?

The Board of Water Supply (BWS) and the Friends of Halawa Xeriscape Garden (FOHXG) offer workshops (currently on hold due to coronavirus pandemic) at the Halawa Xeriscape Garden throughout the year. These classes discuss important rain barrel construction points, installation, proper maintenance, and provide tips on how to easily integrate rain barrels into your gardening lifestyle. For a nominal fee, workshop attendees are given one fully constructed 55-gallon rain barrel. However, interested participants must apply quickly as space is extremely limited. See list of available workshops at the Halawa Xeriscape Garden.

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.


Can I make my own rain barrel?

Step-by-Step Instructions

Constructing your own rain barrel catchment system can be fun and easy! Step-by-step instructions and FAQs are available 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

Also, do you have a plastic barrel you want to convert into a rain barrel but need assistance in drilling and threading the hole? Well you're in luck! 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.

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.

rain barrel

Updated: 11/06/2020