Water 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, some 30-60,000 people in this state rely on catchment systems for their basic water needs. 

Time was, catchment systems were deemed inferior to “piped” public water. In the past, limited inventory coupled with the desire of (especially) off-island purchasers to obtain respite from cramped housing spaces has made the issue of catchment very much a “non-issue.” This is especially true in East Hawaii where rainfall amounts generally ensure tanks are kept generously full. 

Featured image: This oceanfront home on Moana Kai Pali St. features a new 10,000-gallon cement water tank.

Go Big

While I don’t pretend to be an expert on the technicalities of catchment systems, there are a few practical considerations related to value to which I can speak with some authority. First, size matters. Smaller tanks may provide sufficient supply, but most insurance companies require a tank of at least 6-8000 gallons. 

Tank and Filter Types

Types, styles, and filtration systems are personal preference. 

  • Doughboy tanks were common in the past. They are the least expensive and easiest to install.
  • Galvanized tanks are considered an upgrade and tend to last longer. 
  • Redwood tanks, not commonly used any longer, are found in some older homes. Most were installed before 1978 so the possibility that lead-based paint was used on the interior exists. 
  • Other variations such as cement, hollow tile, fiberglass, and plastic tanks are generally enclosed and felt to provide superior tasting water. Additionally, they seem to provide added protection against intrusion by leaves and rodents. 

The best systems include “screening” for the gutter systems, use particulate in-line filters, and provide additional purification or disinfection appliances. UV systems have increased in popularity over the past few years as price and functionality have become more user-friendly.

And, by-the-way, cute little birds using the” pond” on the cover as a birdbath is not a good thing. 

Testing the Waters

Several laboratories test water quality. These are listed in the phonebook (under Laboratories) or call the Dept of Health at 974-4000 ext 64258 for assistance. Most REALTORS® can explain the basics but better yet, hire a professional home inspector who will explain maintenance and function. Some will even perform basic analysis and testing. For more information, visit or ask your REALTOR® for a copy. It’s not likely to show up on any best-seller list, but it should certainly be required reading for even the most catchment savvy households!

By-the-way, wanna know what’s up in your neighborhood? Contact me today to find out how to receive a report tailored to your neighborhood. 

About the Author

Denise Nakanishi

Denise Nakanishi is a REALTOR Broker with Hawai'i Life. Denise Nakanishi is one of Hilo's most acclaimed real estate agents. She reached the rank of Major in the US Army and is now known by many as "Major Mom." The nickname fits–not only does Denise bring the discipline and mission-oriented attitude you'd expect, she's also caring and compassionate, always looking out for her clients like they're her own family. Having made the Big Island her home since 1987, Denise combines her extensive knowledge of the area with a sharp focus on customer service and the results speak for themselves. She's the recent recipient of the Best East Hawai`i, Best of Zillow, Chairman's Circle Award, President's Circle, Top Producing Agent since 2001, and Realtor of the Year awards. Denise stays ahead of the curve because she's passionate about education–she served as Education Chair for Hawaii Island REALTORS® for many years. She's one of Big Island's best real estate resources, known for her weekly article in the Hawaii Tribune Herald. Denise leads Team Nakanishi for Hawai`i Life, who is committed to their family, work, and community. In her little time away from work, Denise is a committed runner and Grandy. She also devotes many hours to various Veterans' Organizations, the East Hawaii Cultural Center, and the Hawaii Island REALTORS®. You can email me at or via phone at (808) 936-5100.

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August 24, 2019

Aloha Denise,
I called you a couple weeks ago to set up a time to chat about rainwater catchment for household use and consumption. You would have an opportunity to update your information for your clients with new technology that outperforms UV systems.

Call or stop by our store in Pahoa Market Place next to Pahoa Fresh Fish Monday – Thursday 10am to 3pm. Its your chance to be a leader for your real estate clients.
Whether your client is listing or purchasing you can encourage them to bring the catchment system to a condition that can be safely used for household use and consumption.

Thank you for highlighting water catchment as a viable source towards becoming sustainable with earth’s resources.

Uncle Tilo’s Water Catchment

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