[PDF]Hawai Rain Harvesting Guide

Rainwater 1
Catchment
Systems



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Acknowledgments

The author wishes especially to thank the following people
for reviewing the manuscript and providing valuable in-
sights and perspectives: Melvin Hamano, Hawaii Depart-
ment of Health, Safe Drinking Water Branch; Deborah J.
Ward and Carl I. Evensen, CTAHR Department of Natu-
ral Resources and Environmental Management; Geeta K.
Rijal, Department of Microbiology and Water Resources
Research Center, University of Hawaii at Manoa; and B.
K. Blesh.

Thanks are also due the many rainwater catchment
system users who answered survey questions and al-
lowed their systems to be photographed, as well as to
the commercial vendors who provided insight and photo
releases, including Peter Epperson, Pacific Gunite; Verne
Wood, Puna Water Services; Mike Greenslaw, Paradise
Pools; Kevin Bradley, Chem-tainer; Terrence Hart, Safe
Water Systems; and Dennis DeNooy, Front Street Manu-
facturing LLC. Thanks go also to the Hawaii County
Fire Department; to CTAHR colleagues Samir A. El-
Swaify, Mike Robotham, Dale Evans, and Miles Hakoda;
and to Hawaii Department of Health-Safe Drinking Wa-
ter Branch chief William Wong and staff members Stuart
Yamada, Michael Miyahira, and Donald Yasutake.

Funding for printing this document was provided in
part by the Hawaii Department of Health* and in part by
the U.S. Department of Health and Human Services through
a grant to Rural Community Assistance Corporation, which
is dedicated to assisting rural communities achieve their
goals and visions by providing training, technical assis-
tance, and access to resources. Many thanks go to these
organizations for their financial support and efforts to en-
hance the quality of life in Hawaii's communities.



*Disclaimer:The views and recommendations contained
in this document are the views and recommendations of
the author, not of the Hawaii Department of Health. Be-
cause many variables affect the quality of water gener-
ated by a rainwater catchment system, the Hawaii De-
partment of Health does not endorse the concept that
water of drinking-water quality may be achieved or
maintained in all instances through compliance with the
recommendations contained in this document.



About this publication

The information contained herein is subject to change
or correction. Procedures described should be consid-
ered as suggestions only. To the knowledge of the au-
thor, the information given is accurate as of December
2001. Neither the University of Hawaii at Manoa, the
UH College of Tropical Agriculture and Human Re-
sources, the United States Department of Agriculture,
the agencies providing funding for printing, nor the au-
thor shall be liable for any damage or injury resulting
from the use of or reliance on the information contained
in this publication or from any omissions to this publi-
cation. Mention of a company, trade, or product name
or display of a proprietary product does not imply ap-
proval or recommendation of the company or product
to the exclusion of others that may also be suitable.

This information may be updated in more recent
publications posted on the CTAHR Web site, ctahr.hawaii.edu>. For information on obtaining addi-
tional copies of this book, contact the Publications and
Information Office, CTAHR-UHM, 3050 Maile Way
(Gilmore Hall 119), Honolulu, HI 96822; 808-956-7036;
808-956-5966 (fax); e-mail .

Important notice

Users of chemicals such as household bleach for water
treatment do so at their own risk. Most of these prod-
ucts are not labeled for use in rainwater catchment sys-
tems. Use of a commercial product as a biocide for sani-
tation purposes is subject to the limitations, restrictions,
precautions, and directions given on the product label.



Guidelines on Rainwater Catchment Systems for Hawaii
Patricia S. H. Macomber

Copyright 2001 ©

College of Tropical Agriculture and Human Resources,
University of Hawaii at Manoa

CTAHR Resource Management publication no. RM-12
ISBN 1-929325-11-8



Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June
30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University
of Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii without
regard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.
CTAHR publications can be found on the Web site or ordered by calling 808-956-7046 or sending e-mail to ctahrpub@hawaii.edu.



2



Guidelines on
Rainwater Catchment Systems

for Hawaii

Patricia S. H. Macomber
Department of Natural Resources and Environmental Management
College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa



An estimated 30,000 to 60,000 people in the state
of Hawaii are dependent on a rainwater catch-
ment system for their water needs. The major-
ity of those people are located on the island of Hawaii
in the Puna, Kau, and Hamakua districts. With proper
design, maintenance, and water treatment, a rainwater
catchment system can provide water that is relatively
free of contamination, soft, clear, and odorless; this wa-
ter can be used for drinking, bathing, washing, flushing,
laundry, and gardening/ But if the system is not prop-
erly designed and maintained, it can be a source of seri-
ous health risk and illness.

It is very important that those using water from a
rainwater catchment system understand all of the po-
tential dangers. In Hawaii, there are no government agen-
cies overseeing the safety of your catchment system. It
is up to you as the owner or user of the system to know
how to maintain the water source and use it in a manner
appropriate for yourself and your family.

This publication is for people who are building or
maintaining a rainwater catchment system. It is intended
to help them improve the quality of their water supply.
While there are too many variables to make any system
100 percent safe, this publication should help you recog-
nize problems, and it also suggests ways to minimize
them. It starts with the premise that from the raindrop to
your faucet, the whole system affects the quality of the



water you use. The information is organized into six sec-
tions, as follows:

1 Water collection — how to catch the water, how much
water you need

2 Water storage — what to keep it in

3 Catchment system maintenance — identifying prob-
lems, keeping the tank clean

4 Water treatment — sources of water contamination,
principles of water treatment

5 Water testing — keeping tabs on water quality

6 Firefighting concerns

Many people using a rainwater catchment system
have never noticed a problem with their water system.
This could be because they do not have any problems,
but it may also be due to the fact that problems with
water systems are not always obvious. Some problems
may take years to show up, and then it is too late. Some
people can be immune to many water-tank pathogens,
or they may be infected but not show symptoms, but a
visitor could drink the same water and become ill. Like-
wise, a healthy adult may not become ill, but an elderly
person or an infant — people that are particularly sus-
ceptible to illnesses caused by contaminated water —
could become deathly ill from drinking water from the
same catchment system.



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Guidelines on Rainwater Catchment Systems for Hawaii



Table of Contents



Introduction 3

Water pollution hazards for rainwater catchment

systems 6

1. Water Collection 7

Building materials 7

Roofing 7

Gutters 7

Screens 8

First-flush diverters 8

Downspouts 9

Water use 10

Rainfall 11

2. Water Storage 15

Type of tank 15

Swimming pool tanks 15

Corrugated steel tanks 16

Enclosed metal tanks 17

Concrete tanks ("cement" tanks) 17

Hollow tile tanks 17

Solid-pour concrete tanks 18

Ferroconcrete tanks 18

Redwood tanks 19

Fiberglass tanks 19

Polyethylene (plastic) tanks 20

Undesirable storage containers 20

Tank liners 20

Tank covers 21

Tank overflow devices 22

Drain pipes 23

House intake pipes 23

Adding other water to tanks 23

Tank location 23

Tank foundations 24

Pumps 24

Earthquakes 24

3. Rainwater Catchment System Maintenance ... 25

Tank maintenance 25

Sludge removal 25

Dead animals in the tank 25

Leaf and organic decomposition 25



Other problems with catchment water 25

Bacterial, viral, and parasitic worm diseases 26

Protozoans 26

Lead 26

Acid rain 27

Some bacterial illnesses associated with water ... 28
Some protozoan diseases associated with water.. 30
Other diseases associated with water 30

4. Water Treatment 33

The solutions to water contamination 33

Electrical wires and rats 33

Disinfection 34

Using chlorine in the water storage tank 34

Why almost everyone should purify

catchment water with chlorine 35

Concerns about using chlorine 35

What chlorine doesn't do for you 35

Other disinfection techniques 36

Filters 36

Coarse filters 36

Faucet, under-sink, and pitcher-type filters .... 36
What is the best system for you? 36

5. Water Testing 39

Water testing — a snapshot in time 39

How to get water tested 39

Microbiological testing 40

Total coliform 40

Fecal coliform 40

Heterotrophic bacteria 40

Inorganic contaminant testing 40

Other water testing 42

Other organic chemicals 42

pH 42

Turbidity 43

Color, odor, taste 43

Trucked-in water 43

6. Firefighting Concerns 45

Notes and References 47

Pump Systems for Rainwater Catchment 50



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Guidelines on Rainwater Catchment Systems for Hawaii



Water pollution hazards for rainwater catchment systems



Many sources of pollution can affect rainwater catchment systems. A few of the contamination problems you need to consider when living on
rainwater catchment are illustrated in this drawing. Few of these problems are insurmountable. With awareness, planning, and good catchment
system management practices, your water supply can be improved.



Erupting volcanoes, fireplaces, and other sources of combustion produce
smoke and fumes containing particulate matter that can land on your roof
and wash into your water supply. Gasses from these sources also can
combine with moisture in the atmosphere to produce acid rain.



Agricultural fields nearby can be
sources of pesticide drift if sprays
are applied incorrectly.




Trees and shrubs that
touch or overhang the roof
and gutters can cause
several problems. Plant
debris can block gutters
and downspouts so water
can't get to the tank.
Decomposing organic ma-
terials provide nutrients for
microorganisms and can
taint the water so that its
color and taste become
unappealing. Plants also
host insects, birds, and
other animals whose
wastes and corpses can
contaminate your water
supply. Rats in particular
are a potential source of
disease, and they are
adept at getting onto roofs
via branches and utility
wires.



Uncontrolled tank overflow can undermine
a tank's foundations, resulting in eventual
tank collapse. This runoff needs to be
directed to avoid causing problems on your
property or your neighbors'.



Downspouts that are not properly designed hold water
between rains. This water is not affected by water
purification treatments applied to the tank, and it stagnates
while waiting for the next rain to flush it into the water supply.



Birds delight in the baths formed by sagging mesh tank covers or
blocked gutters. Many insects, particularly mosquitoes, find these pools
perfect for breeding. Holes in the cover allow critters direct access to
your stored water. Rodents and larger animals such as chickens and
cats have fallen through holes in tank covers and drowned.



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Guidelines on Rainwater Catchment Systems for Hawaii



Section 1



Water Collection



Building materials

The key to choosing building materials for a rainwater
catchment system is to select and use materials that will
not leach toxins into the water under either normal or
acid rain conditions. The material should be both non-
toxic and inert (nonleaching). Acid rain, which is pro-
duced in Hawaii as rain mixes with volcanic emissions,
causes certain metals and other materials to leach much
more than normal rain would. The more acidic the rain at
your location, the more likely you are to have a problem
with chemicals leaching from materials the water touches.

Roofing

Ideally, only materials approved by the Food and Drug
Administration or the National Sanitation Foundation
would be used to catch drinking water. Unfortunately,
no roofing materials have been approved for drinking
water catchment use. The National Sanitation Founda-
tion has approved epoxy coatings for drinking water use
that can be painted over a surface, but these coatings are
very expensive, have an effective life span of only about
seven years, and were made for coating the interior of
tanks rather than roofs and gutters.

The most common type of roofing material used for
water catchment is galvanized metal that has been
painted or enameled with a nontoxic paint. Other ma-
terials that could be used are concrete, terracotta tiles,
slate, polycarbonate, and fiberglass/ 2 ' Paint used on the
roofing material should not contain fungicides or other
poisons that could leach into the water. Materials con-
taining lead should not be used anywhere in the catch-
ment system. Lead is a serious problem with older homes
because not only the paint but also nails, flashings, sol-



ders, and gutters could contain lead. Lead-based paint
was not manufactured in the United States after 1978,
but these paints were still in circulation after that time,
so if your home is an older home it would be wise to
have the paint checked. Simple, inexpensive test kits
can be purchased at local hardware stores to test paint
or surfaces for lead. In addition to lead, avoid using roofs
that contain uncovered zinc, asbestos (which used to be
mixed with concrete tiles), tar, asphalt, or pesticide-
treated wood.

With a new roof, always divert the first flush of rain-
fall away from the catchment system. The first rain will
help flush away dust and debris such as metal shavings
from the new building materials and keep these materi-
als out of your tank. Also, new acrylic paint used on
roofing and gutters can leach substances including de-
tergent into your catchment water, which could cause
the water to froth. (2)

In designing a roof for catchment purposes, keep its
pitch relatively low to maximize the amount of water
that gets into your gutter. A steep roof can cause water
to splash out of the gutter.

Gutters

Like roofs, gutters should be made of inert materials.
PVC or plastic gutters are the most common. Because
gutters are not likely to be made of food-grade material,
try to select materials that are as inert as possible. Be
wary of colored materials that could contain toxic dye
or fungicide.

When installing gutters, make sure that there is a
continuous downward slope toward the catchment tank.
Low areas that cause a backflow or puddling must not



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Guidelines on Rainwater Catchment Systems for Hawaii



be allowed. Standing water can collect insects, attract
animals, and catch organic materials, such as leaves. De-
caying organic material can ruin the taste and color of
the water and cause health problems.

Screens

One method to keep large debris such as leaves out of
your catchment system is to place screens over the gut-
ters. The screens then have to be maintained to remove
any build-up of debris that would block water from en-
tering the gutter.

It has been suggested that screens be placed at an
angle so that leaves and other things caught on the screens
will slide off. However, most gutter systems have outer
lips that are too high to accommodate such an angle.
Various types of gutter netting and screening are avail-
able; some arch over the gutters, which allows greater
access for water when leaves get caught around the sides,
but these types still have to be cleaned regularly.

Some people block the downspouts with screens.
This catches large debris, but like all other screens, regu-
lar cleaning is needed to prevent clogging. Most homes
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