RAINWATER CATCHMENT SYSTEMS

Displayed above is a picture of our roughly 10,000 gallon water catchment tank.   Based on our annual rainfall of over 150" of rain and roof size, our catchment system is capable of harvesting over 200,000 gallons of free water a year.  The tank has a liner approved by the FDA for storing food and water.  The FDA has not approved a roofing material or gutters for drinking water but steel roofing and non-toxic gutters are used.  The downspouts and other pipes to the catchment tanks are regular plastic plumbing components.

Just like municipal water, catchment water should be treated before being used.  Here's what a typical system looks like:

The pump and pressure tank in the lower left of the photo pulls the water in from the catchment tank and pressurizes it. Water being held under pressure, the pump doesn't need to run every time a spigot is opened. It also ensures good water pressure even if you have all the showers, sinks, and toilets running at the same time. Two filters (one of them charcoal) remove impurities from the water. A UV sterilization unit kills any microscopic organisms that may have made it past the filters.   Before the water is made into ice or consumed many people prefer an additional combination charcoal filter under the sink or in the refrigerator. Some homes use reverse osmosis or other treatment methods. 

Because most newer homes have solar hot water, the water tank is 80 gallons or larger so extra hot water is stored for dark cloudy days. It has the ability to heat the water with electricity as a backup, using a timer to save power. However, we seldom run out of hot water and keep the electricity to it turned off. The system is capable of heating the water extremely hot- like to scalding. But because the system is not designed for that pressure it stops circulating the water through the solar collectors at a pre-set temperature. Any temperature above 150 will shorten the life of the tank, and the higher the temp, the shorter the life span. Ours is set at about 140 F. (most electric or gas home units are set at about 120). Because 140 degree water can burn the skin an adjustable mix valve mixes the hot water coming out of the heater with cold water before it enters the home so we don't get scalded. Ours is set at about 120.

Do people on catchment systems ever run out of water? We haven't, but it does happen.  Several water delivery companies service the community by delivering a tanker load of water into empty catchment tanks or to fill swimming pools.  Additionally, the counties provide free spigots where households can get potable water for drinking and other uses.

You may be wondering... what about sewer? Many homes without municipal access were built with cesspools, but building codes now require new construction to use septic systems. 

For more information, the state of Hawaii publishes a water catchment guide:  https://www.ctahr.hawaii.edu/hawaiirain/Library/Guides&Manuals/A_Guide_for_Rainwater_Catchment_Systems_in_the_Pacific_Portia_Franz.pdf

DISCLAIMER

Dayna Robertson and EXIT Realty Island Living are not affiliated with, endorsed by, or connected to the State of Hawaii, University of Hawaii (CTAHR), Hawaii Department of Health, EPA, Hawaii County, or any government agency regulating rainwater catchment, water quality, or public health. All information, examples, estimates, personal experiences, and the linked CTAHR guide on this page are for general informational and educational purposes only. Private residential rainwater catchment systems in Hawaii are largely unregulated; water quality, safety, treatment, and maintenance are the sole responsibility of the owner/user. No representations or warranties are made regarding accuracy, completeness, safety, potability, or fitness for any purpose. Use at your own risk. For official guidance on design, treatment, testing, health risks, or regulations, consult:

• Hawaii Department of Health Safe Drinking Water Branch (health.hawaii.gov/sdwb)

• UH CTAHR rainwater resources (ctahr.hawaii.edu/hawaiirain)

Seek qualified professionals (plumbers, water specialists, engineers, health experts) for property-specific advice, installations, or real estate decisions.