1. HES 3112 –Water Resource Engineering 2011
The Use of Rainwater Tanks to Supplement Water Supplies: Urban
Water Issue Assignment
Sharifah Nur Azureen Binti Wan Osmani (4224698)
Tang Sieu Wei (4239547)
4224698@students.swinburne.edu.my
4239547@students.swiburne.edu.my
ABSTRACT
Rainwater tanks to supplement water supplies is an innovative technology where it can directly
benefits our state by reducing demand on water supply, save money, save energy and so on
There are a lot of advantages and as well as disadvantages in implement this method. The use
rainwater tanks to supplement water supplies are suitable to implement a sustainable water usage
practice in Malaysia.
KEYWORD
Rainwater Tanks; Sustainable; Water Supplies; Rainfall; Sarawak; Rainwater Harvesting
System
INTRODUCTION
Malaysia has one of the highest rainfalls in the world at an annual average close to 3,000mm for
west Malaysia and 4,500mm for Sabah and Sarawak. However, this does not mean that the
country has unlimited access to supplies clean water. The challenge now is for the water industry
in Malaysia to overcome the paradox which more flooding occurs and irregular supply of water
for consumer. A rainwater tank is a water tank which is used to collect and store rain water
runoff, typically from rooftops goes through the rain gutters. Rainwater tanks are devices for
collecting and maintaining harvested rain. Rainwater harvesting has thus regained its importance
as a valuable alternative or supplementary water resource, along with more conventional water
supply technologies. Rainwater tanks are installed to make use of rain water for later use, reduce
mains water use for economics or environmental reasons, and aid self-sufficiency. The capacity
of a harvesting system depends on the amount of rainfall, size of collection area, storage
capacity, and the household level of demand for water.
Sharifah Nur Azureen
Tang Sieu Wei 1

2. HES 3112 –Water Resource Engineering 2011
METHODS AND DISCUSSION
(1.0)Review of the selected topics
There are many ways to implement a sustainable water usage practice in Malaysia and one of
them are the use of rainwater tanks to supplement water supplies. The reason we choose this
topic as urban water issue assignment is because Malaysia is one of the country that received
highest rainfalls amount of rainwater in the world that is annual average close to 3000mm for
west Malaysia and 4500mm for Sabah and Sarawak. This fact shows that Malaysia is suitable for
the rainfall harvesting technology to achieve a sustainable water usage practice.
Besides, among all the other topics available, we think that this topic is the best to implement a
sustainable water usage practice in Malaysia because this is a simple practical method to
supplement water supplies whereas every house will be able to do this by themselves and
practice this method in saving water and one step ahead to achieve the awareness of Malaysian to
be sustainable in usage of water.
(2.0)Benefits
Rainwater acts as sustainable water supply option where rainwater can be utilized alone or
together with other supply sources in residential, commercial and industrial projects where pure
water is desired. Rainwater collected by rainwater tanks is suitable to use when there is a
uniform rainfall pattern in the area and even though a few days without rain, we still have a
reliable alternative water source nearby. Stored water can be used when the dry season
happening, when the groundwater is limited and contaminated, electricity and water prices are
rising, when storms and disaster strike and for bushfire prevention purposes.
Rainwater can be used throughout the year for all domestic purposes. For example, rainwater is
used for gardening, drinking, washing car, and other. The available water should be well
managed and make sure that have enough storage capacity to bridge the dry period or where
good quality water supplies are limited.
Besides that, rainwater storage can be provided for bushfire prevention purposes. One of the
benefits is to access the mains water to encourage the conservation of water. Installing a
rainwater tank will reduce the average household bill significantly. Rainwater tanks are the best
solution to the water restrictions during the current times of drought. In addition, in rural areas,
rainwater is usually unpolluted before reaching the ground. It means that the rainwater from
well-maintained roof catchments is most commonly safe for drinking. The rainwater are also
ideal for consumers that must restrict salt or chlorine intake because most of the tap water are
already mix the chlorine inside the water and this might not be good for the consumer.
2 The Use of Rainwater Tanks to Supplement Water Supplies: Urban Water Issue Assignment

3. HES 3112 –Water Resource Engineering 2011
(3.0) Advantages
Rainwater harvesting is a popular household option as the water source is close by, convenient
and requires a minimum of energy to collect it. The users can maintain and control the household
systems without the need to rely on the other members of the community. Operation and
maintenance of a household catchment system are solely by the tank owner’s family at any
times. As such, this is a good alternative to poor maintenance and monitoring of a centralized
piped water supply, this is the advantages that use of rainwater tanks to supplement water
supplies. Rainwater harvesting systems have been implemented successfully since almost all
roofing materials is suitable for collecting rainwater.
Rainwater harvesting is a simple low-cost technique that requires minimum specific expertise
and offers many benefits. The rainwater tanks built is no demands on public funds and can save
the cost. It can provide an important source in some places that relatively high rainfall spread
throughout the year. Water supplies from rainwater tank are more convenient than water which
needs to be carried. Collected rainwater can supplement other water sources when they become
scarce or are of low quality. It also provides a good alternative and replacement in times of
drought or when the water table drops and wells go dry.
Besides that, rainwater tanks can be found in all the great civilizations nowadays. The
construction of rainwater tanks can be very simple and local people can easily be trained to build
by themselves. It can reduce costs and encourages more participation, ownership and
sustainability at community levels. One 20-litre container of clean rainwater collected from the
roof can save a walk of many kilometers to the nearest clean water resources. Besides small
containers, large sub-surface and surface tanks also can be used for collecting larger amounts of
rainwater.
The use of rainwater from water tanks is a useful alternative when many piped water supply
systems fail to increased need for water results in lower groundwater tables and depleted
reservoirs. The availability of water from sources such as lakes, rivers and shallow groundwater
can fluctuate strongly. Collecting and storing rainwater can provide water for domestic use in
periods of water storage. Rainwater can be used for multiple purposes such as watering gardens,
washing cars, flushing toilets, agriculture, and in washing machines. It also can be used for
drinking especially when other water supplies are unavailable, expensive or poor quality, and
that safety measurement is taken that the water is not contaminated or the water is periodically
filtered. Rainwater may also provide a solution when the water quantity is low during the dry
season in rivers or other surface water resources.
One of the advantages of collecting and storing rainwater it is to improves the accessibility and
convenience of water supplies and has a positive impact on health. So, rainwater is generally of
good quality and better than other available or traditional sources. Other advantages of use
rainwater tanks to supplement water supplies are low environment impact. Rainwater is a
renewable resources and no damage to the environment. Rainwater is also not affected by local
geology or topography. Rainwater collection always provides an alternative wherever rain falls.
Sharifah Nur Azureen
Tang Sieu Wei 3

4. HES 3112 –Water Resource Engineering 2011
(4.0) Disadvantages
Some of the disadvantages of using rainwater tanks to supplement water supplies are high initial
investment cost, regular maintenance, storage capacity limits the supply, insecure water quality,
uncertain climate, and some other factors.
The high initial investment cost is one of the disadvantages of using rainwater tanks as an
additional water supply because the cost of constructing the rainfall harvesting system is high
and no profit is obtained until the system is complete and can be used or the cost of the tank and
associated accessories can be high compared to the cost of mains water actually saved. The
payback period is the length of time required to recover the cost of an investment and this is
depend on the size of tank, the volume it can cater, the total rainfall collected, the costing, the
assumption of usage daily and so on. After all the assumption and calculation had been
determined, then the payback period is known. If the payback period of the investment is in long
time, then the adjustment need to be made and we can say that the system is more expensive than
using the main water stream.
Next, the water used for harvesting is full of pollutants which can lead to health issues and this
polluted environment will result in increasing amount of nitrates and fluorides in the water and
bacteriological contamination levels will rise in water. The contaminations of bacteriological
levels rise such that the water inside the tank is exposed to the sunlight which can stimulate algae
growth. Plastic tank for example may allow light to penetrate in and to avoid this, the plastic
should be kept out of the sun or painted with dark color. Besides the contamination of
bacteriological, the need to prevent insect vectors from breeding inside the tank is crucial. By
providing water tanks without any care for prevention from insect breeding can cause problems
than it can be settle, for example, an area where the malaria might present is very dangerous,
safety and care should be taken to prevent this situation from happen. The precautions that can
be take is all the tanks should be sealed to prevent the insect from entering and breeding inside
the water tank. For more safety, the mosquito proof screen can be fitted to the opening of the
tanks.
Rainwater can also be used for drinking and cooking but there are some highest possible
standards are met. However, rainwater does not meet the World Health Organization (WHO)
water quality guidelines but this does not mean that water is not safe to be drink. Gould and
Nissen-Peterson (1999), in their book, point out that the Australian government have given the
all clear for the consumption of rainwater ‘provided the rainwater is clear, has little taste or
smell, and is from a well-maintained system.’ But as we know, the microbial quality of water
collected in tanks is not as good as the urban supplies and for a limited area that has a heavy
traffic and the industrial area, the chemical released may affect the chemical quality of rainwater
and this is not good for health especially the young one. However, there are some
recommendation and aspect that we need to consider when one person want to make rainwater as
drinking water supplies, we should boil the water to 100 degree Celsius to make sure the harmful
bacteria do not present anymore. Next, adding chlorine to the rainwater in a right quantity will
disinfect the water.
4 The Use of Rainwater Tanks to Supplement Water Supplies: Urban Water Issue Assignment

5. HES 3112 –Water Resource Engineering 2011
Moreover, the limited space is one of the disadvantages for using rainwater tank to supplement
water supplies in daily life. Adoption of this technology requires a high cost and space area
which making it less attractive to some governmental agencies to use this technology and
become sustainable. This are also the reason many people just used the tap water instead of
rainwater because they do not have to provide a space for the rainwater tank. However this will
not be a problem to a individual or a residents area to use this technology because each house
only require small amount of water compare to the governmental agencies and this does not
include for drinking but only for washing, car wash, gardening, and so on. Generally, the bigger
the catchment area, the bigger space required and the larger amount of rainwater can be
collected.
Next, the regular maintenance is required when installing the rainwater harvesting system for the
good flow of the water from the catchment area then through the pipe until it reached the tank.
Some of the debris may block the flow of rainwater to the tank and this may affect the amount of
water collected and the hygiene if no maintenance is done. The water from water tap is readily
available in any hour and we as a consumer do not have to do a regular maintenance for the
water and this can save many times and save budget. The maintenance is not only cleaning the
debris periodically but it is also required the maintenance in the material used where some of the
materials may worn out in time and this also need a cost to maintain it in a good condition.
Even though the regular maintenance is often and causing a lot in cash, the payback period can
be achieved in a short period of time, hence, this method is not actually a bad idea at all for
making the rainwater tank as the supplement for the water supply.
The other disadvantages of using rainwater as the supplement water supply is the inconsistency
in climate, even though Malaysia received a huge number of rainfall amounts, it does not mean
that the rainfalls amount is the same everyday and there will be rain daily. From the observation
obtained from Malaysia Metrological Department, the records for the monthly rainfall amount
are different for all the states and division, for example for December 2010 and January 2011,
the rainfall amount received in Kuching is 350mm (December) and 700mm (January); figure 1
and 2. As we all know, the La Nina phenomenon that Is still active in January had causing most
area in Peninsular, Sabah and Sarawak were still experiencing wet weather and received total
rainfall from average to very much above the monthly average. Whereas for December, the
Northeast monsoon were still in active phase of this season lasts from November to
January and during this season period, the east coast of peninsula, the coast of Sarawak and
eastern coast of Sabah would experiencing a few comprehensive heavy rain that go continuously
as long as three days as results from the surge monsoon. However, for Sarawak specifically for
Kuching the rainfall amount are in normal distribution. From this fact, obviously, we can see that
the inconsistency of rainfall for every month which can result an insufficient amount of water
when the rainfall amount per month is small.
Lastly, there are also other disadvantage such as the rainwater tank may be dangerous to children
who play around it and the rainwater harvesting system are often not part of the building code
and lack clear guidelines for users or developers to follows and others.
CONCLUSION
Sharifah Nur Azureen
Tang Sieu Wei 5

6. HES 3112 –Water Resource Engineering 2011
In conclusion, the usage of rainwater tanks to supplement water supplies is the best choice to
implement a sustainable water usage in practice in Malaysia. The rainwater acts as the alternative
water supply for the daily usage such as domestic purposes, emergency purpose and even for the
commercial purposes. This method is convenient, cost-efficient for small area covered and
requires a minimum of energy to collect the rainwater. This method is also suitable for the rural
area where the access of clean water may be insufficient and it is an easy installed system. On
top of all, rainwater tank to supplement water supplies is a suitable method to implement a
sustainable water usage practice for Malaysian.
REFERENCES
6 The Use of Rainwater Tanks to Supplement Water Supplies: Urban Water Issue Assignment

7. HES 3112 –Water Resource Engineering 2011
Agua (2010), Agua solution : Fundamentals of rainwater harvesting,
http://www.aguasolutions.com/fundamentals-en.html, viewed on 1 May 2011
Anonymous (2009), Level of services: water sanitation,
http://web.mit.edu/urbanupgrading/waterandsanitation/levels/provide-water-supp.html, viewed on 3May
2011.
Anonymous, (2009), Rainwater Harvesting in Delhi, Rainwater Harvesting in Delhi,
http://wwfenvis.nic.in/pdf/rain.pdf, viewed on 30 April 2011DVdesign, (2005),
Aussie (2009), The Benefits of Getting a Rainwater Tank Installed,
http://www.aussiewatersavers.com.au/freereport.pdf, viewed on 30 April 2011
Australian government department of health and ageing (2004), Guidance on Use of Rainwater Tanks, ISBN 0 642
82443 6, Australian government, publications production unit (Corporate support branch), PDF files, page 2
Http://www.nphp.gov.au/enhealth/council/pubs/documents/rainwater_tanks.pdf , visited on 2May 2011
Bacha (2008), Rainwater harvesting for domestic use,
http://www.rainfoundation.org/fileadmin/PublicSite/Manuals/AGRODOK_RWH_43-e-2006-small.pdf,
viewed on 2 May 2011,
Dupont. P, (2010), Technical Manual: Rainwater, Australia's guide to environmentally sustainable homes website
http://www.yourhome.gov.au/technical/fs73.html#disadvantages, visited on 30 April 2011
Harvesting (2005), Rainwater Tanks: Which rainwater tank is ideal for rainwater harvesting, Rainwater harvesting
guide website
http://www.rain-barrel.net/, visited on 1 May 2011
Jay R.Smith (2009), division of smith industries, A green idea: advantages of rainwater harvesting,
http://www.jrsmith.com/green_building/rainwater_harvesting_advantages_benefits.htm viewed on 2 May
2011
Lili (2009), Low-impact living initiative: Rainwater Harvesting,
http://www.lowimpact.org/factsheet_rainwater_harvesting.htm, visited on 3 May 2011
Meteorological Department Malaysia (2010), Monthly Weather Bulletin,
http://www.met.gov.my/index.php?option=com_content&task=view&id=849&Itemid=1586, viewed on 1
May 2011
Rainwater, savewater.com.au website,
http://www.savewater.com.au/index.php?sectionid=632, viewed on 29 April 2011
APPENDICES
Sharifah Nur Azureen
Tang Sieu Wei 7

8. HES 3112 –Water Resource Engineering 2011
Figure 1: Rainfall Amount (January 2011)
Figure 2: Rainfall Amount (December 2011)
8 The Use of Rainwater Tanks to Supplement Water Supplies: Urban Water Issue Assignment