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A Guide

ToRainwater

Harvesting inMalaysia

Written By:

Jitender Dev Sehgal President 2005 – 06

Rotary Club of Johor Bahru4N Susur3, Jalan Tun Abdul Razak,80000 Johor Bahru, Johor, Malaysia

This booklet is distributed as a Community Service byRotary Club of Johor Bahru, District 3310 of RotaryInternational. Contents of this booklet may be copied freely

with acknowledgement of the source, and used only for freedissemination of information to public.

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FOREWORD

Carl-Wilhelm Stenhammar, 2005 – 06 President of

Rotary International, in his Theme Address to 2005

International Assembly at Anaheim, USA, stated that

‘The United Nations calls the global water crisis “athreat to economic development, to povertyreduction, to the environment, and to peace andsecurity.” …… and more than one billion people don’thave clean, safe drinking water.’ He urged the

Rotarians all over the world to do what they can and

improve the availability of clean water in the world.

The Author, Rotarian Jit Sehgal, in this year of his

Presidency of the Rotary club of Johor Bahru, inspired

by the RI President, has written this guidebook to

remind Malaysians on how to harness this primary

natural resource of clean water that is delivered free

to our rooftops, by Mother Nature. The author is ahighly qualified chemical engineer, with more than

fifty years of experience in industry and is eminently

positioned to research and write on this topic. The

content of this booklet deserves serious attention by

all.

Although the Country enjoys abundant resource of

fresh water, already there are areas where water

supply becomes inadequate, and rationing is resorted

to. Following the guidelines of this booklet, no doubt,

will benefit the population, and the environment as

stated in the booklet, both in the short and long term.

Ir John Cheah Kam Loong P.I.S Johor Bahru

Past District Governor 1990-91 November 19, 2005

Rotary International District 3310

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��������Introduction

Water is an essential component forsustaining life. Life on our planet as weknow it would not have come into beingwithout it, nor can it be sustained in theabsence of water. Our bodies consistmostly of water. We need water fordrinking, cooking, washing, agriculture,to run our industries, and fortransportation on the waterways, and ina myriad other ways that form part of oureveryday living. For as long as water isabundantly available, we take it forgranted; when in scarcity however itbecomes our most precious resource. Askany desert dweller about water tounderstand its real value.

Did you know that although 70% of ourearth is covered with water, only 3% ofthis water is fresh? Out of this, 2% islocked up in the form of ice, and it is onlythe balance 1% of water that recyclesthrough the evaporation / condensationcycle, that flows into the rivers and lakes,to be used by mankind.

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The history of rainwater harvesting inAsia can be traced back to about the 9thor 10th Century to the small-scalecollection of rainwater from roofs andsimple brush dam constructions in therural areas of South and South-east Asia.Rainwater collection from the eaves ofroofs or via simple gutters into traditionaljars and pots has been traced backalmost 2,000 years in Thailand.Rainwater harvesting has also long beenused in the Loess Plateau regions ofChina.

In Malaysia, we are blessed with anample supply of water thanks toabundant rains. However, increasingusage by our industry, in agriculture andby household users is straining ourexisting water supply infrastructure. Thecosts of adding to this infrastructure andthat of replacing the ageing system arefurther burdening our Exchequer.

At present we primarily depend uponrainwater that falls over the hills and inthe countryside and which is thencollected into large reservoirs and asground water. This water is thenpumped into treatment plants and from

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there distributed through the watermains and a network of pipes.

However perhaps we should pause tothink that clean water is also beingdelivered to us right on our roof tops asrain but that we let this run off into stormwater drains, where it ends up causingflooding and soil erosion on its way to therivers and sea. In fact, the rainwaterfalling on our rooftops is one of thepurest forms of natural water that natureprovides us, yet we simply let it flowaway.

This booklet presents some usefulinformation on rainwater, and aims toprovide an understanding of many of therelevant aspects of rain with a view toharvesting it for both domestic andindustrial use directly from our rooftops,thereby allowing us to benefit from thisbountiful resource delivered free to us bynature. A simple method of harvestingrainwater, storing and using it isdescribed.

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��������The Water Cycle

The never-ending exchange of waterfrom the atmosphere to the oceans andback again is known as the hydrologiccycle. All forms of precipitation (hail, rain,sleet, and snow), and consequently allmovement of water in nature, forms partof this cycle.

Precipitation stored in streams, lakes andin soil evaporates while water stored inplants transpires to form clouds, whichboth absorb solar heat and form thestore of water in the atmosphere. Whenthe atmospheric conditions reach a levelof super saturation, a state achieved as aresult of increased humidity combinedwith changes in temperature andpressure, this water is released in theform of rain, sleet, snow or hail, whichfalls as a result of the force of gravity tothe earth.

This cycle continues, and results inshifting water from sea level all the wayinto the mountains and back into rivers,lakes and the sea etc.

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��������Quantitative estimates of waterresource in Malaysia

According to the InternationalCommission on Irrigation andDrainage1 “Rainfall (in Malaysia)generally occurs throughout the year, butthere is some concentration due to theNorth-East and South-West monsoons.The mean annual rainfall averages about2,300 mm, while the annual potentialevaporation averages about 1,500 mm.

The total annual surface water resourceis estimated to be 566,000 million KL peryear and of this 26 % is in PeninsularMalaysia, 54 % in Sarawak, and theremaining 20 % in Sabah. Groundwaterresource is estimated to have a safeyield of 14,700 million m3 per yearin Peninsular Malaysia, 5,500 millionKL per year in Sarawak, and 3,300 millionKL per year in Sabah.

The present annual total consumptiveuse of water is estimated to total 10,400million KL for irrigation. 4,900 million KLfor domestic and industrial water supply.On the whole, Malaysia has sufficientwater resources for development to meet

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all the demand provided there isproper water resourcesdevelopment, conservation andmanagement.”

��������Rainfall in Johor:Figure shows the monthly rainfall patternin Johor for the period 1971 – 20012.

Mean Rainfall in Johor 1971 - 2001

0

50

100

150

200

250

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Month

It is to be noted that monthly rainfall inJohor averaged at 187 mm with amaximum of around 230 mm occurringduring monsoon periods.

Thus, on a typical rooftop catchment’sarea of 100 sq m, average monthlyincidence of rainfall is estimated at 18.7KL (equivalent to roughly three barrels of

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200 liters each day). This is a significantamount of water sufficient to meet mostof the requirements of a typical Malaysianhousehold.

��������Benefits of RainwaterHarvesting:

There are many benefits to be derivedfrom harvesting this bountiful flow ofrainwater on our rooftops.

For the user, the benefits to be derivedare:

� Independent and ample supply ofwater in the dwelling.

� Water received is free of costs.Use of this water significantlyreduces water bills for purchasedwater from municipal supply.

� Costs incurred for purifying thewater for potable use are nominal.

� For users located in the ruralareas, an independent supply ofwater avoids the cost of installinga public water supply system.

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For the environment, there are manyadvantages as well:

� Harvesting rainwater is not onlywater conserving, it is also energyconserving since the energy inputrequired to operate a centralizedwater system designed to treat andpump water over a vast service areais by-passed.

� By capturing water directly, we cansignificantly reduce our reliance onwater storage dams. This places lessstress on these water storagefacilities and can potentially reducethe need to expand these dams orbuild new ones. Avoiding having tobuild additional dam reservoirsconsequently avoids ecologicaldamage to the area to besubmerged.

� Rainwater harvesting lessens localsoil erosion and flooding caused bythe rapid runoff of water fromimpervious cover such as pavementsand roofs as some rain is insteadcaptured and stored. A reducedlevel of storm water require smallersized storm water drainage systemsand also helps in reducing soilerosion into the waterways,

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preventing damage to thesurrounding areas.

� Secondary use of grey water (wateronce used in showers etc.) furtherreduces the need for processingeffluent water in treatment plantsbefore discharge into thewaterways.

For the Government:

� Reduce the burden for newinvestment to build, operate andmaintain additional water supplysystems such as reservoirs, watertreatment plants and distributionsystems necessary to meet the ever-increasing demands for water.

� Save on land area committed tostore water in artificial lakes built forthe purpose

Collecting the rain that falls on a buildingto be used nearby is a simple concept.Since the rain harvested in this manner isindependent of any centralized system,this activity promotes self-sufficiency andalso helps to foster an appreciation forthis essential and precious resource.

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��������Rainwater quality

Water quality is a term used to describethe chemical, physical, and biologicalcharacteristics of water, usually in respectto its suitability for a particular purpose.Although scientific measurements areused to define water’s quality, it's not asimple thing to say that "this water isgood," or "this water is bad." After all,water that is perfectly good to wash a carwith may not be good enough to serve asdrinking water. When the average personasks about water quality, he probablywants to know if the water is goodenough to use at home, to play in, toserve in a restaurant, etc., or if thequality of water is suitable for aquaticplants and animals.

Rainwater has a distinct advantage overother water sources in that it is one ofthe purest sources of water available.Droplets of rainwater contain mainly thefollowing impurities:

� Dissolved oxygen from the air incontact (beneficial to living beings)

� Dissolved carbon dioxide from theair (like that in soda water, but toa much lesser content)

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� Nitrogen oxides formed by thunderlightening (imparts very diluteacidity to the water)

� Sulfur dioxide gas contained in thecombustion gases from burning offuels on the ground (imparts verydilute acidity to the water)

However, the impact of thesecontaminants on water purity is negligiblefor most uses. Although the pH of rain isbelow neutral, it is only slightly acidic,and the smallest amount of buffering canneutralize the acidity. The low totaldissolved salts and minerals levels foundin rainwater allow for minimal addition ofneutralizing chemicals to adjust the pH tonear neutral where necessary.

Upon contact with surfaces such as roofs,gutters etc., the water may pick upsoluble and insoluble impurities andmicrobial contaminants that it comes incontact with. The amount of impuritiespicked up naturally depends upon thematerial used for the construction of thesurface over which the water runs, andits state of cleanliness. In Malaysia,

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where most roofs are built fromterracotta or ceramic tiles, with a slopingorientation, and frequent rainfall, theaccumulation of debris is minimal, andwhat there is, is easily washed awayduring the first flush of rain. It isimportant to ensure that this washingaway does take place becausecontaminants such as dried leaves fromtrees, bird droppings, settled dust onrooftops need to be excluded. Installingvery simple traps to bypass the initialportion of rainwater ensures that onlyclean water is collected.

With this provision of automaticallyseparating the first flush ofrainwater prior to collection intostorage, rainwater quality almostalways exceeds that of ground orsurface waters since rainwater doesnot come into contact with soil androcks where it may dissolve saltsand minerals. Further, it is notsubject to many of the pollutantsthat often are discharged intosurface waters such as rivers, andwhich can contaminategroundwater.

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It should be noted however thatrainwater quality could be influenced bythe locality where it falls since localizedindustrial emissions will affect its purity.Thus, rainwater falling in non-industrialized areas will probably besuperior to that in cities dominated byheavy industry.

Aesthetic concerns such as color, taste,smell, and hardness comprise thesecondary testing criteria used toevaluate publicly supplied water. Whenassessed according to thesecharacteristics, rainwater proves to be ofbetter quality than well or municipal tapwater. Inorganic impurities such assuspended particles of sand, clay, and siltfound in groundwater contribute to thewater’s color and smell.

Rainwater is the softest natural occurringwater available, with a hardness of zerofor all practical purposes. When usedwith detergents for washing purposes, itcan significantly reduce the quantity ofdetergents and soaps needed forcleaning, as compared to typicalmunicipal tap water. Additionally, soapscum and hardness deposits disappear,and the need for a water softener, often

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an expensive requirement for well watersystems, is eliminated. Water heaters andpipes will be free of deposits caused byhard water and should last longer.

Rainwater’s purity also makes it anattractive water source for certainindustries for which pure water is arequirement. This is of particular interestto industries where pure water isproduced using expensive and energyintensive processes, such as computermicrochip manufacturing, electroniccomponents, pharmaceuticals and certainfood industries. Since rainwater containsalmost no dissolved minerals and salts itapproximates distilled water quality. Forpeople on restricted salt diets, thisrepresents a decisive advantage overother water sources.

Caution: If it is intended to be usedas drinking water, it is advisable tosubject the rainwater to testing by aCertified Test Laboratory to conformto potable water standards.

����Water needs of a typicalhousehold

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Water is needed for various purposes.Some of the uses can be consideredessential while some others may fall inthe category of being peripheral innature.

a. Essential Uses:

This category consists of uses forwater that are related to food andhygiene in a household. Theseare:

� Toilets flushing – typically 7 Lper flush

� Floors mopping and washing –typically 20 L per room eachtime.

� Bathing (personal and pets) –typically 10 L per minute in ashower.

� Washbasin usage – typically 5 -10 L per minute while brushingteeth and shaving etc.

� Clothes washing – typically 100– 150 L per wash cycle.

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� Machine dishwashing – typically 50 Lper dishwater cycle.

� Hand dishwashing – typically 5 – 10 Lper minute under a running water tapin a washbasin.

� Cooking (potable)

� Drinking (potable)

b. Peripheral Uses:

� Gardening – typically 10 - 15 L perminute from a gardening hose. 5 – 10 Lper minute from a sprinkler head(depending upon size of the sprinklerhead and water pressure).

� Washing of cars, motorbikes etc. –typically 10 L per minute from a washspray gun.

� General outdoor washing

The actual quantity of water usage by ahousehold therefore depends on thenumber of occupants, user habits,number of vehicles maintained,gardening needs, and the physical sizeof the household premises.

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����Quantitative potential ofharvesting from the roof tops

For Households: As mentioned earlier,Malaysia receives 2,300 mm of rainfall onthe average, during a year. Based on acatchment’s area of 100 sq m (typicalrooftop size of an average dwelling) thisamounts to receiving 230 KL of rainwateron a roof in a year.

As noted above, in order to ensure thatonly clean water is collected for use, it isessential to segregate the initial rainfallthat may contain contaminants such asbird droppings, dried leaves, dirt etc. thatwould have collected on the catchment’sarea between rainfalls. Typically 50 L ofthe initial rain falling on a 100 sq. m areaneeds to be discarded. Since rain occursintermittently throughout the year thenumber of times roof washings need tobe diverted depends upon the number ofrainy days in a year. While detailedreliable data of rainy days is not available(and varies from year to year),conservatively one may assume thatrainfall occurs over half the number ofdays in a calendar year. Thus an

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estimated amount of 10 KL of rainfallneeds to be discarded annually ascontaminated water before collection ofclean water for domestic use.

Therefore it is reasonable to assume thatapproximately 220 KL of clean rainwatercan be collected from a 100 sq. mcatchment’s area of domestic rooftop,providing an average daily supply of 600L (approx three barrels of 200 L)available water for use. For mosthouseholds in Malaysia, this constitutes amajor part of the water consumed. Thebar chart below shows the averagemonthly rainwater that may be collectedfrom a 100 square meter roof topcatchment area.

Further, since rainfall is an intermittentphenomenon, sufficient storage capacityneeds to be made available to create abuffer and ensure that there is acontinuous supply for use.

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Monthly Estimated Rainwater

Harvested

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5

10

15

20

25

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Feb

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Ju

n

Jul

Aug

Sep O

ct

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Month

M3/

Mo

nth

For Industrial Users: The potential forharvesting rainwater for industrial uses isgreater due to the availability of muchlarger rooftop catchment areas. Inestablishments, using multiple buildingsand sheds, centralized collection tanksshould be considered. Typically, totalcatchment area of 10,000 Sq. M providesa potential rainwater collection of 23,000KL annually. Due to a very low mineralcontent, demineralization of this watermakes it attractive for uses as boiler feedwater, and other applications where softwater is used. Significant savings in costsare envisaged.

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��������Rainwater Harvesting Method

Rainwater is harvested using aninstallation of pipes and tanks in anarrangement that allows for automaticallydiverting the first flush of rain that iscontaminated with dirt etc deposited onthe catchment’s area followed bycollection in a storage tank for furtheruse. The installation also includes asystem of supply to water user outlets viapumping or gravity depending upon thearrangement. In certain instances,provisions may also be made for chemicaldosing and water filtration.

��� Components of anInstallation:

The Installation for rainwater harvestingconsists of the following components.

Catchment Area: Catchment area is thesurface area from which rainwater can becollected as clean water. Usually, thiscomprises the roof over a house, and anyassociated covered portions of thedwelling, including sheds, factory roofsetc. that are situated above ground level.

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Concreted or tiled pathways should notbe included, since these surfaces arenormally heavily contaminated with dirt,oil spills, soil bacteria etc. The size of aroof catchment area is the building’sfootprint under the roof. The catchmentsurface is limited to the area of roof,which is guttered. A simple method tocalculate the size of a catchment areawould be to multiply the length and thewidth of the guttered area that forms theboundary of the catchment surface.Often, the roof area is divided intoseveral guttered zones. A sum of allthese areas provides the total catchmentarea that is available for rainwaterharvesting. Caution: Rainwater collected fromsurfaces containing lead should notbe considered for any potable use.

Gutters: These are the transportchannels often shaped as half rounds, oras ‘V’ or ‘U’ shaped open top channelsthat are placed to collect the water runoff from the catchment area. Gutters arenormally adequately sized to allow flowof all the collected water from thecatchment area during heavy downpourconditions. It is advisable to install wire

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mesh screens over the gutters to avoidclogging of the downspout attached tothe gutters. The outside face of thegutter should be lower than the insideface to encourage drainage away fromthe building wall.

Downspouts: These are vertical orslanting pipes that receive water from theGutters and transfer the collected waterinto roof washers. An adequately sizeddownspout should be able to handle allthe rainfall collected from the catchmentarea. Downspouts designed to handle 5cm of rainfall during a 10-minute periodare considered adequate. Downspoutsare typically made of the same materialas the gutters but of a smaller crosssection.

Roof washer: This is a purpose builtcombination of a screen to collect debristhat may have fallen on the catchmentarea during dry periods between rainfallsand a stand pipe (or a small container) ofsufficient volumetric capacity to receiveand by-pass the first flow of rain andwash away any dirt, bird droppings etc.that may have collected on it beforecollecting clean rainwater into the storagetank. It is a simple device with no moving

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parts, located at a convenient and easilyaccessible height. It requires occasionalattention to clear away accumulateddebris if there is any. The device consistsof a funnel with a wire mesh screen fittedon it, with a standpipe of 150 to 200 mmdiameter underneath (or a container),that collects the first flush of rainfall.Once it has filled up with the first flush ofwater, the rest of the water overflowsinto the downspout connected to thestorage tank. The roof washer is sizedto collect at least 30 liters of waterfor every 100 sq m of catchmentarea. One has the option to either drainaway the water in the roof washer or useit for any non-potable purpose ratherthan wasting it. One must be extracareful about roof washing, if thecollected rainwater is to be used forhuman consumption.

Specially designed automatic diversionvalves are also used as roof washers todrain away the initial flow of rainfall priorto collection, as an alternative to theabove method. However, these are notcurrently available in local market.

Note: Trimming of any treebranches that overhang the roof is

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strongly recommended since thesebranches are perches for birds andproduce leaves and other debris.

Piping: The connection between thestandpipe and storage tank is a pipe ofsufficient size to allow rapid flow of cleanrainwater into the storage tank. PVC orGalvanized Iron pipes are commonly usedfor this purpose.

Storage Tank: A storage tank ofsufficient capacity to receive hold andsupply rainwater forms an important partof the installation. The tank should besized such that it maximizes thecollection of rainwater from the availablecatchment area, and also providessufficient storage capacity to meet thewater needs between refills withrainwater.

For an average household, a StorageTank of 1,000 L – 2,000 L capacity (tocollect rainfall on 100 sq m catchment’sarea) is considered adequate in view ofthe frequent rainfall pattern in the region.

There are several factors to be taken intoconsideration while selecting a suitable

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location for a tank. Among the importantones are:

Space and aesthetic considerations– a tank may be located above or belowground depending upon space available,and harmonizing with the surroundings.If supplementary water were to bereceived occasionally from road tankers,easy access to the tank for this purposewould be an important consideration.

Hygiene – the tank should be placed inlocations away from sources of pollutingsmells such as toilets, animal shelters,septic tanks etc. This is of particularimportance if the water is to be used forpotable purposes. The tank should alsobe easily accessible for inspection,addition of chemicals (when needed) andease of cleaning out when necessary. Atight-fitting cover is essential to preventevaporation, mosquito breeding, and tokeep insects, birds, lizards, frogs androdents from entering the tank. A tanklocated in a shaded area away fromsunlight, helps in keeping the storedwater cool, reducing the incidence ofalgal and bacterial growth in the storedwater.

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Elevated Location – a tank located at aheight obviates the need for pumping outthe water for ground level usage such aswashing of cars, gardening etc. However,a pump will be necessary to supply waterto any user points above the level of thetank. A tank filled with 1000 liters ofwater weighs over a ton. Care should betaken to provide supports and foundationsufficient for the size of the tankinstalled.

Water storage tanks can be either ofprefabricated type or built on site.Prefabricated tanks made of Polythene,PVC, Stainless Steel, Galvanized Iron,Precast Cement, Fiberglass, are readilyavailable. Tanks may also be built on siteusing reinforced cement concrete ormasonry. Such tanks should be suitablywaterproofed and sealed, to preventcontamination of contained water.

Water Treatment: As mentionedearlier, the rainwater as it falls on thecatchment’s area is very clean, andcontains minimal impurities. However,once rain comes in contact with thecollection surface, it can wash manytypes of bacteria, molds, algae, protozoaand other contaminants into the collected

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water. Health concerns related tobacteria, such as salmonella, e-coli andlegionella, and to physical contaminants,such as pesticides, lead, and arsenic, arethe primary criteria for drinking waterquality analysis. Falling rain is free ofmost of these hazards. Choice oftreatment depends upon its ultimate use.

If the rainwater is intended for use insidethe household, either for potable usessuch as drinking and cooking or for non-potable uses including showering andtoilet flushing, appropriate filtration anddisinfection practices must be employed.

If the rainwater is to be used outside forlandscape irrigation, where humanconsumption of the untreated water isless likely, the presence of contaminantsmay not be of major concern and thustreatment requirements can be lessstringent or not required at all.

Rainwater contains almost no dissolved

minerals and salts and is near distilledwater quality. Total dissolved mineralsand salts levels average about 10milligrams per liter (mg/L). TotalDissolved Solids (TDS) can range as highas 50 mg/L and as low as 2.0 mg/L.

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These values are very low whencompared to city tap water, makingrainwater virtually sodium free. The pH ofrainfall would be 7.0 if there werenothing else in the air. However, as rainfalls through the air, it dissolves carbondioxide that is naturally present in the airand becomes slightly acidic. The resultantpH is 5.6; however, any sulfates ornitrates dissolved from the air will lowerthis number below pH 5.6. Although thepH of rain is below neutral, it is onlyslightly acidic, and the smallest amountof buffering can neutralize the acid. Thelow total dissolved salts and mineralslevels found in rainwater permit evenvery small amounts of baking soda (onelevel tablespoon per 500 liters) to adjustthe pH to near neutral. If you plan to useyour harvested rainfall for drinking water,have the water tested by a certifiedlaboratory.

Conveying: Depending upon thelocation of the storage tank and thelevel at which the water is to be used,delivery system for the treatedrainwater may be either by gravity orthrough a pump.

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���Typical HouseholdInstallation:

Figure below shows a scheme ofarrangement to provide forpressurized discharge of water usingan automatic operating pump.

Roof Washer

Down pipe

Drain Drain

Level Indicator tube

Low Level Switch

Rain Water Harvesting System

PressureSwitch

Power Supply

Rainwater Supply Pump

Rainwater Storage Tank

Wire Screen

To outdoor use

Indoor Overhead TankFor toilets, Washbasins, Showers etc

From Water Mains

Leaf Screen and Roof washer:This consists of a simple standpipe (typicallya PVC pipe of 150 mm diameter) of sufficientlength (or a container) to accommodate 30 –50 liters of water, fitted with a coarse screenon a funnel at the top to trap leaves etc. Ithas a valve at the bottom to drain away thewashings collected into it (alternatively, thedrain valve can be replaced with a weep hole

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for slow self draining). A 50 mm pipebranches from near the top and is connectedto the collection tank to receive overflow ofthe rainwater for collection after the roofwasher is filled up with the initial flow ofrain. The roof washer may be locatedadjacent to the storage tank, to allow forshort piping connection to it.

Cisterns or Storage Tanks: Typically aplastic water tank of 1000 – 1500 Litercapacity is used. The tank should be locatedat a height of approximately one meterabove the ground for easy discharge ofwater.

Conveying: For transfer of water to indooroverhead tank, an inline water filter must beinstalled. Installing a second inlet connectionbelow the rainwater inlet connection shouldprovide for make up of water from municipalmains. This arrangement ensures receivingof municipal water when the water level inthe indoor tank drops to a level thatautomatically opens the valve connected tomunicipal supply.

A gardening hose suffices for the purpose ofuse of water for garden uses, car washing,and floor washing etc.

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Water Treatment: None or minimaltreatment may be necessary for non-potableuses of this water. Use of two tablespoonfulof household bleach may be added to a fulltank to avoid growth of algae in the tank.

Use of two heaped tablespoons of bakingsoda (to neutralize acidity) and twotablespoonful of household bleach (forsafeguarding against growth of algae) isrecommended for a 1000 L of watercollected.

It is to be noted, that rainwater mustnot be used for drinking or cookingpurposes unless it has been tested forpotability by authorized testinglaboratory and certified as fit for thispurpose.

��� Estimated Cost of installing aSystem for a Household: Breakdown of an estimate for asystem that is adequate for ahousehold to collect and store 1000 Lof rainwater is given below. Actualcost however may vary according tothe particular location and type ofsystem adopted.

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Estimate of Cost for Installing aRainwater Harvesting System

ITEM Cost RM

Storage tank (1000 L fibreglass) C/w feed funnel & Strainer 600Water Pump 450Pipes and valves 200Electric connection 75

Total 1,275(Excludes transport and labor cost)

������������Tips for reducing water usage:

General: � Practice routine common sense

leak detection.� Periodically “zero read” water

meter for leaks� Replace worn valves, faucet

washers, O rings

In the Bathrooms and toilets:� Install ultra-low flush toilets � Use water-wise showerheads

that use 10 l per minute

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� Use faucets that flow at 5 L perminute.

� Minimize running the water tapwhile brushing teeth and shaving

� Turn off shower while soapingthe body.

� Take shower of approx. tenminutes or less.

� Check the toilet tank for leakageinto the toilet bowl. To do this,add food color to a toilet tank.Appearance of color in the toiletbowl shows a continuous leakand wastage of water.

In the kitchen:� Avoid pre-rinsing of dishes before

loading dishwasher. � Soak dishes before hand washing

to remove stubborn deposits.� Avoid overloading clothes washing

machine and thus need forrewashing.

� Always run full load of clotheswash.

� Peel and clean vegetables in abowl of water instead of in runningwater.

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Car washing:� Use pressure spray gun for rinsing

the car after soap.� Avoid using open-ended hose.� Use bucket and sponge for

soaping the car.

Watering the lawns:� Use a sprinkler instead of flooding

the lawn with water. Use a cutopen empty sardine can on thelawn to know how much water hasbeen sprinkled.

� Water your lawns in the morningor evening to minimizeevaporation loss.

� Use hand held shower bucket forwatering the plants, shrubs etc.instead of flooding the beds.

� Use a layer of organic mulcharound the plants to reduceevaporation of water.

Careful implementation of these measurescan reduce water consumption by up tothirty percent.

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��� Acknowledgements:

Some of the information contained inthis Guide has been garnered fromvarious sources on the Internet. Dueto the varied nature of the sources, itis not physically possible toacknowledge these sourcesindividually.

Professor Dr. R Narayanan, Professorof Civil Engineering, University ofManchester, England, for reading themanuscript and making valuablesuggestions for improvements.

��� References:1. International Commission on

Irrigation and Drainage, 48 NyayaMarg, Chanakyapuri, New Delhi,India

2. Water Resources Unit, Hydrology& Water Resource Division,Department of Irrigation &Drainage, Malaysia

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������������BIBLIOGRPHY1. Domestic Roof water Harvesting

Research Programme,Development Technology Unit,School of Engineering, Universityof Warwick, UK.

2. Water Resource Research Center,College of Agriculture and LifeSciences, University of Arizona,USA.

3. Gould, J. E., 1992, RainwaterCatchment Systems for HouseholdWater Supply, EnvironmentSanitation Reviews No. 32,ENSIC,Asian Institute of Technology,Bangkok, Thailand.

��������Disclaimer

Readers are advised to ascertain theaccuracy and reliability of theinformation contained in thisdocument independently.

The author(s) and/or distributors ofthis document shall not be heldresponsible for any loss or damagethat may arise directly or indirectlyfrom the use of the informationcontained in this document.

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About the Author:Jitender Dev Sehgal was born in Lahore in undivided India (now inPakistan), and migrated to New Delhi during the partition of theCountry. He obtained a Degree Bachelor of Science with Honours inChemistry from the University of Delhi and a second Degree ofBachelor of Science in Chemical Engineering from the Institute ofTechnology, Banaras Hindu University in India. He went on to therenowned Massachusetts Institute of Technology, Cambridge,Mass., USA, where he earned a Masters Degree in ChemicalEngineering in 1959. While at MIT, he worked as a ResearchScientist, carrying out research into methods for ultimate disposalof radioactive wastes from nuclear power reactors. Upon return toIndia, he worked as a Research Scientist in the well-known BhabhaAtomic Research Centre in Mumbai. He then moved to work withUnilever Research Laboratories in India and Europe where over thenext 20 years he developed his career in research in chemicaltechnology development. He relocated to Malaysia in 1979, and hasworked in various managerial positions in the palm oil refiningindustry in the country for over 25 years. His interest inenvironment protection, and developing environment friendlymanufacturing processes has continued throughout his workingcarrier as a research scientist as well as CEO of various companies.He has played a key role in establishing a unique manufacturingplant for recycling industrial wastes generated by the palm oilprocessing industry in Malaysia, thus allowing that industry to avoidpolluting the environment. He is currently Managing Director of aMalaysian Company offering innovative technological solutions toprocess industrial wastes.

The author has been a committed member of the RotaryInternational since 1980. He is a member of the Rotary Club ofJohor Bahru, and was also a Charter Member of Rotary Club ofPasir Gudang. He has held various positions in these Clubs, beforebecoming the President of Rotary Club of Johor Bahru 2005 – 06.

This booklet is the result of his personal and professional interestsand the inspiration given by Carl-Wilhelm Stenhammer, President ofRotary International 2005 – 05, who has stressed the importance ofconserving world’s water resources for the future.

The author may be contacted by e-mail: jdsehgal@tm.net.my

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