Rainwater Catchment

How to make a home rainwater catchment system safe for domestic use

  • Rainwater catchment systems on individual homes are not regulated by the Department of Health (DOH). Home owners that intend to use rainwater collected off their home’s roof can take action to help make the water safe for domestic use. To enhance safe water quality and reduce the need for treatment and corrective action, a catchment system should be well designed, regularly maintained, and periodically tested.
  • Careful design and construction with the right materials is important to reduce the potential for chemical contamination. The system should be designed to protect against disease carrying animals.
  • Regular and periodic maintenance, including cleaning of the system roof, tank, gutters, and filters will also reduce potential water contamination.
  • Testing catchment water will help assure that water in the system is safe, or will determine that action must be taken to make the water more suitable.
  • For greater assurance that rainwater catchment water is safe for consumption, DOH recommends that system owners implement the following actions:
    • Follow the recommendations contained in: “Guidelines on Rainwater Catchment System for Hawaii” by the University of Hawaii College of Tropical Agriculture and Human Resources. These guidelines can be downloaded from this link. Additional resources may be found on the University of Hawaii Sea Grant website
    • Consider installing a certified filtration/treatment system to remove contaminants of concern to you. These devices are certified for removal of specific contaminants by organizations such as the National Sanitation Foundation (NSF), Underwriters Laboratories (UL) and the Water Quality Association (WQA). These certifications are good for the contaminants that are listed on the certification. Do not assume that they remove contaminants that are not listed.
    • Perform and pass a screening test for E. coli bacteria, turbidity, lead and copper using a laboratory certified or approved by the DOH to perform these drinking water analyses. A list of certified laboratories can be found at this link. Water sampling must follow proper procedures to assure accurate test results. A qualified sampler will be required. The sample must be taken from a point after all treatment has been applied such as at your kitchen tap. Use of the certified laboratory and referenced EPA Test Method guarantees the quality of the sample results.

      In order to pass the screening test, the sample must meet the following Acceptable Levels using the listed EPA Test Method:

                                                                                  Screening Test and Acceptable Levels

Parameter Acceptable Level EPA Test Method
Turbidity <= 5 NTU 180.1
Escherichia coli (E. coli) = Absence SM 9223 (Colisure or Colilert)
Lead <= 0.015 mg/L 200.8
Copper <= 1.3 mg/L 200.8

                                           NTU = Nephelometric Turbidity Units
                                           mg/L = milligrams per liter = ppm

  • While the requirements here are less rigorous than what is required of regulated drinking water, DOH believes that these actions, appropriately applied, should help assure that a rainwater catchment system is safe for domestic use.

Subsidized Testing for Lead and Copper

DOH – Safe Drinking Water Branch currently subsidizes the testing for lead and copper in individual homes served by rainwater catchment systems. Owners or users of rainwater catchment systems can take advantage of the program once per year. Under this program, the owner or user of a “legal dwelling” can submit a water sample from their rainwater catchment system to a participating analytical laboratory for testing of lead and copper in the water.

The owner must pay for the shipping of the sample and $25.00 for the analyses. The DOH will be billed for the remaining cost of the analyses. AECOS Laboratory, Inc. is currently the only lab approved by DOH, and is participating in this program. The owner should ask the laboratory if they participate in the DOH subsidized lead and copper testing program. Due to the contractual nature of the analytical work, the DOH cannot pay for analyses of any other contaminants or work submitted to any other laboratory.

Information on water test kits is available at this link.

More Information

Additional precautions should be taken by rainwater catchment users during periods of increased volcanic activity. Information on these as well as other suggestions for rainwater catchment system operation and maintenance can be found in the document Precautionary Measures for Residential Rainwater Catchment Users During Volcanic Activity.

The Veterans Benefits Administration of the Department of Veterans Affairs issued Circular 26-14-4 on February 19, 2014, titled “Clarification of the Department of Veterans Affairs (VA) Acceptance of Water Catchment Systems in the State of Hawaii.” Per Item No. 4, “[t]his Circular is rescinded January 1, 2016.”

For Frequently Asked Questions on Rainwater Catchment Policy, please click here. For more information, see http://www.hawaiirain.org. Please note that the University of Hawaii Manoa – Cooperative Extension Service’s Hilo office number published in the Guideline booklet and on the CTAHR website for availability and purchase of the fecal test kits, pH and CL2 test strips is no longer valid.

Contact Us

Phone: Oahu: 586-4258
Hawaii: 974-4000 x64258
Maui: 984-2400 x64258
Kauai: 274-3141 x64258
Molokai and Lanai: 1-800-468-4644 x64258

Fax: (808) 586-4351
E-Mail: sdwb@doh.hawaii.gov

Safe Drinking Water Branch – Oahu
919 Ala Moana Blvd., Room 308
Honolulu, HI 96814-4920

Safe Drinking Water Branch – Hilo
Hawaii District Health Office – Hilo
1582 Kamehameha Avenue
Hilo, Hawaii 96720
Phone: (808) 933-0401
Fax: (808) 933-0400

Last Update: 3 July 2017