Catchment “101”

You may be surprised to learn that homes all over the world depend on catchment systems. The report “Guidelines on Rainwater Catchment Systems for Hawaii” estimated that in 2010, between 30,000 and 60,000 people in Hawaii relied on catchment systems for their basic water needs. In the past, catchment systems were considered inferior to public piped water. However, the combination of limited housing inventory and the desire of off-island purchasers for more space has made the issue of catchment much less significant. This is particularly true in East Hawaii, where abundant rainfall typically keeps tanks generously full.

Practical Considerations of Catchment Systems

While I don’t claim to be an expert on the technical aspects of catchment systems, there are several practical considerations related to value that I can speak to with confidence.

First, the size of the tank matters. While smaller tanks may meet basic supply needs, most insurance companies require tanks to hold at least 8,000 gallons. The type, style, and filtration system of the tank is a matter of personal preference.

Types of Catchment Tanks

In the past, Doughboy tanks were common due to their affordability and ease of installation. Galvanized tanks are seen as an upgrade and tend to last longer. Other variations, such as cement, hollow tile, fiberglass, and plastic tanks, are generally enclosed and believed to provide better-tasting water. These tanks also offer added protection against leaves and critters entering the water supply.

Filtration and Disinfection Systems

The best catchment systems use screens for gutter systems, incorporate particulate in-line filters, and include purification or disinfection appliances. UV systems have become increasingly popular over the past few years, as their cost and functionality have become more accessible. However, one thing to keep in mind: birds using the tank cover as a birdbath are not ideal!

Older Catchment Systems and Lead Concerns

Redwood tanks, which are no longer commonly used, can still be found in some older homes. Most of these tanks were installed before 1978, so there is a possibility that lead-based paint was used on the interior. It is advisable to have the water tested for quality, and several laboratories provide this service. You can check with the Department of Health for more information.

Get Professional Advice

Most REALTORS® can explain the basics of catchment systems, but it’s better to hire a professional home inspector who can explain the system’s maintenance and functionality. Some inspectors also perform basic water analysis and testing.

Where to Learn More

For the complete and updated guidelines, visit Hawaii Rainwater Catchment, or ask your REALTOR® for a copy. While this document may not be a bestseller, it should be required reading for even the most catchment-savvy households!