Specific Guidance for Water Catchment Systems

For households utilizing roof-collected rainwater tanks as their water source:

• Roof safety: Previous eruptions have led to injuries from falls during roof cleaning or maintenance. It is important that you have the proper equipment, skill and experience to work on the roof, and if not, hire a licensed contractor to do any work.
• To prevent contamination of your tank water, cover the water tank with a tarp and disconnect the downpipe. Wait until rainfall has thoroughly removed tephra or someone has manually cleared the tephra from the roof and gutters before reconnecting the downpipe to your tank.
• Contamination of drinking water by tephra fall can occur. This can lower the pH to undesirable levels and potentially toxic elements can leach from the tephra.
• Small amounts of tephra fall (several millimeters in thickness) are unlikely to render water unsafe for consumption, although the water may develop an unpleasant metallic or sour taste. Over time, subsequent rainfall will dilute tephra-related chemicals and enhance water quality.
• If tephra has entered your rainwater tank, consider using your emergency water rather than your tank water supply for drinking and food preparation until official guidance is issued and/or there has been water quality testing.
• Tank water may continue to be used for purposes other than drinking and food preparation, such as for cleaning and washing.
• Have a filter for the intake in your water catchment tank. For water systems employing pumps, ensure that the tank outlet is positioned well above any settled ash at the bottom of the tank to minimize the risk of drawing ash into the pumping equipment, which may result in equipment damage.
• Water quality in a catchment system can be tested before using it again for drinking water. The US Environmental Protection Agency (EPA) recommends that drinking water pH be between 6.5 and 8.5, with neutral pH 7 being ideal. A pH below 6.5 is acidic and can corrode pipes, potentially leaching metals like lead or copper into your water, causing a metallic taste. Rainwater in Hawai‘i is commonly below pH 6.5, due to volcanic emissions creating acidic rainfall. A pH above 8.5 is basic (alkaline), which is generally safe but can taste bitter, feel “slippery,” and cause scale buildup in pipes and appliances.
• Testing water for pH can be done easily at home using pH test strips (litmus paper), liquid test kits, or digital pH metersfor higher accuracy. Simply dip the test strip or probe into a water sample, compare the color change to a chart, or read the digital display to determine if the water is acidic (0-6), neutral (7), or alkaline (8-14).  Since pH is a field test, it is best done at home with regular field monitoring or test strips.
• If the tank water pH is too low (acidic), sodium bicarbonate (baking soda) can be used to raise the pH to the targeted levels.
• Drinking water test kits are available at local hardware stores or online and cost about $25-30. Some water kits test for pH, fluoride, copper, lead, bacteria and other minerals.  Check the label on the kits before you buy for the parameters tested.  The advantage of test kits are they are quick providing immediate results, easy to use, cost effective, portable and user-friendly.  However, test strips may produce inaccurate results, miss low concentrations, and have limited shelf life.
• Experience with past eruptions indicates that elevated fluoride in water is possible. With prolonged exposure, too much fluoride can weaken bones and teeth. Up to the present time, fluoride concentrations found in catchment systems have almost always been below the Maximum Contaminant Level (MCL) of 4.0 mg/L (or 4 ppm) for fluoride established by the US EPA for public water systems. However, if you are concerned about fluoride concentrations because you are in a tephra fall zone as depicted in the Kilauea Summit Eruption Map for January 24, 2026, or have been impacted by tephra, the water can be tested for this parameter out of an abundance of caution.
• Typical testing for water catchments independent of volcanic eruptions includes turbidity, E. coli, lead and copper. The Department of Health Safe Drinking Water Branch (“DOH SDWB”) can subsidize the testing for “legal dwellings” for lead and copper. (See Resources Section below under DOH SDWB).  This testing can be subsidized once per year, per residence, and the shipping and handling for copper and lead can be combined with fluoride.  According to the DOH SDWB website, AECOS Laboratory is currently the only lab approved by DOH for their copper and lead subsidized testing program.
• The homeowner should contact the DOH SDWB (email: sdwb@doh.hawaii.gov & phone: 808-586-4258) and/or AECOS Laboratory (email: aecos@aecos.com) for more details on participation in the subsidized testing program for lead and copper.
• Some other companies that can be contacted to determine whether fluoride testing can be performed and the costs are Culligan, Pural, mytapscore, and bigislandhomeinspectors.
• Test strips offer a practical starting point for evaluating drinking water quality, but they should be ideally complemented by more comprehensive testing methods for thorough assessment. Collaborating with neighbors or community members can lower testing, maintenance, and cleanup costs.