The BWS offers Rain Barrel Water Catchment workshops throughout the year at the Halawa Xeriscape Garden. Workshop participants learn about rain barrel water catchment as an alternative and effective method for conserving water outdoors. Here are some commonly asked questions about rain barrel catchment.

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.

Why should you do it?

The Board of Water Supply (BWS) estimates that fifty 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 1000 square foot rooftop - that's enough water to fill twelve large fish tanks! Not only will the use of potable drinking water be reduced, but also the total amount on your water bill.

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.

How can you make your own rain barrel?

Constructing your own rain barrel catchment system can be fun and easy! Step-by-step instructions 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. A list of frequently asked questions (FAQ) is also included in this informational handout. For reference, see this document for barrel dimensions or to view how rain barrels are set up at the homes of past workshop participants.

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 would I place my rain barrel and what kind of maintenance is needed?

Effective placement and routine maintenance of you rain barrel is required to keep it running smoothly and at an optimum level. Information and instructions are available about the optimal area to place your barrel and how to properly maintain it. Also included is how you can connect multiple rain barrels together to increase water storage capacity.

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 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 53-gallon rain barrel. However, interested participants must apply quickly as space is extremely limited. See list of available workshops at the Halawa Xeriscape Garden.

Additional 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.

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