Sustainability 2010, 2, 266-279; doi:10.3390/su2010266
Rainwater Storage Gutters for Houses
School of Engineering, University of Western Sydney, Locked Bag 1797, Penrith South, NSW 1797,
Australia; E-Mail: email@example.com; Tel.: +61-2-4736-0921; Fax: +61-2-4736-8333.
Received: 27 November 2009 / Accepted: 5 January 2010 / Published: 13 January 2010
Abstract: A history of the implementation of a system of water storage roof gutters
illustrates the difficulties which may be encountered in delivering more sustainable
construction systems. Utilizing some rainwater at the site where it falls has considerable
conservation benefit but it requires builders, roofers and plumbers to vary some of their
standard practices. The observed change delivery process involves incorporation of trade
knowledge, attention to detail, flexibility and the willingness of all parties including
local building control authorities to try new options. Lessons learned have implications
for the introduction of many kinds of environmentally driven improvements to
Keywords: storage gutters; rainwater use; potable water replacement; infiltration;
Despite an increased tendency towards building high-rise apartments in some major cities, the
Australian residential construction sector is still largely low-rise and medium or low density.
Individual detached houses, townhouses and villas made up 85% of residences built in 2001 . The
typical housing unit is a three bedroom detached brick veneer with a tiled roof surrounded by lawn and
exotic gardens. Such housing is largely being constructed on the periphery of existing cities and is a
major consumer of land, water and energy resources. It also has significant adverse impact on the
ecology of the surrounding areas . The attraction of such housing, however, remains strong in the
Australian population and consequently it is necessary to find ways of minimizing the environmental
impact of the traditional ways of building and living in the suburbs.
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Researchers have reported on the need to be more efficient in the use of water in urban situations
for some time. Extended droughts in the catchment areas of several major Australian cities in recent
years have meant that a strong focus has fallen on the need to minimize the use of piped water in
housing. There is also an increasing perception reported in the general news media and the broader
research literature that climate change may be leading to generally drier climatic conditions especially
in the south eastern portion of the continent. In response, state governments have introduced incentives
for householders to collect roof water and use it to substitute for piped water in some situations. The
New South Wales government‟s BASIX scheme requires a 30% reduction target in household water
usage and gives credit to home owners for the installation of rainwater storage devices and water
efficient fittings. While this is a welcome development has yet to impact greatly on the existing
housing stock . It has long been standard practice in Australia to build houses with pitched roofs
where rainwater is collected in roof gutters and passed through downpipes to a local stormwater
system which also drains the road surfaces and other hard paved surfaces. The system then passes the
stormwater on through pipes of increasing diameter till at some point it is discharged into a canal or
waterway. Although this was intended to prevent soil erosion and particularly flooding, the actual
result was often an increase in nuisance flooding when drains become blocked with litter and debris.
Large areas of hard paved surfaces prevent stormwater naturally infiltrating the soil. When there is no
blockage the stormwater picks up considerable kinetic energy through its swift passage down the pipe
system and often results in erosion damage at the outlet point into a natural waterway. As a
consequence of these effects, modern urban stormwater design seeks to slow down the passage of
water through the system by such means as detention ponds, rock baffles and restoring streamside
vegetation . In Australia, due to rainfall variability and to state government incentive schemes, there
has been a significant and accelerating trend towards including rainwater collection devices in both old
and new suburban areas [5,6]. The practice of using rainwater to substitute for piped water supply
for some purposes has also been adopted in several parts of the world and in varying climatic
A complimentary approach to these efforts has been the innovation of „roof storage gutters‟ as
rainwater tanks to reduce the input into the stormwater system and replace some of the potable water
that is currently used for secondary purposes. Toilet flushing and garden watering do not require
drinking quality water though it has been standard practice to waste potable water in this way. Storage
gutters replace the use of high quality potable water with rainwater for these secondary purposes. As
the gutter is in fact the tank there is no need for large, visually obtrusive rainwater tanks. The drive to
improve environmental performance is seen as one of the major drivers of innovation in the
construction industry [17,18]. The storyline of the implementation of roof storage gutters has
implications for many apparently small modifications of construction practice for sustainability
improvements which lead in fact to both downstream and upstream changes in standard practice.
2. Characteristics of Storage Gutters
The benefits of this innovation in water storage occur on three levels: the householder, the
community and the environment. Firstly, for the householder, there is reduced consumption of mains
water supply and resulting lower bills. Little maintenance is required and the gutters have long lives
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due to the leaf guard which ensures no rotting vegetation gets in to the gutter. Less water is needed for
the garden because of the associated infiltration system. In medium density attached housing the
savings in space on the ground compared to using water tanks can be significant. Secondly, for the
community, lower demand on the piped water service means less need for new dams. There is also less
need for piped street drainage and area retention systems and consequently lower costs in developing
land for housing. Thirdly, for the environment, there is a more natural level of water infiltration into
the soil in developed areas and a consequent replenishment of the water table. There may even be a
reduction in nuisance flooding and in the erosion hazard of high speed runoff during storms. The
system is, however, a departure from standard practice and as such requires a managed change process
for its successful adoption.
2.1. The Ideas behind Storage Gutters
Roof storage gutters as illustrated in Figure 1 have the advantage of being gravity fed and therefore
not requiring pumps to deliver water for household use. Once an installation is adjusted for household
usage patterns and exterior landscaping it can continue to function and reduce potable water usage
with minimal maintenance or need for other human intervention. A particular advantage that the
storage gutters have over rainwater tanks is that because the water is stored at height, gravity feed is
available for most applications. Pumps are not required to distribute the water and this avoids
additional cost and the possibility of mechanical breakdown. The gutters studied here are produced in
three sizes ranging from 15 litres/metre capacity for the small retrofit gutter, to 25 litres/metre for
standard applications and 48 litres/metre for heavy demand situations. The gutters are designed to be
supported off the roof framing but the large model is sometimes supported off the external wall. They
can replace rainwater tanks in suburban areas as they are much less visually obtrusive and take up no
floor space on a restricted site. They fit into the standard suburban streetscape in way that large
rainwater tanks do not. To date most storage gutter usage has been in standard mass produced housing
or „project homes‟ and examples in architect designed „high end‟ buildings are not available.
Figure 1. Cutaway section of medium sized storage gutter plus diagram showing storage zones.
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In contrast to traditional gutters which are laid with falls to downpipes the storage gutters need to be
laid level for maximum storage capacity. As a result, they collect water from 100% of the roof area,
and not just the plane of roof facing the downpipe. Outlet plugs are installed in the base of the gutters
at suitable locations to feed toilet cisterns, washing machines or garden taps. A mains water top up
valve is provided to ensure that the water level remains sufficient to feed toilet cisterns even in
extensive dry periods. During periods of normal rainfall the storage gutters can replace between 30%
and 60% of mains water usage, depending on local rainfall distribution, household usage patterns and
the collection area of the roof.
2.2. Infiltration Measures
An essential ingredient of the concept of storage gutters is that as well as storing water for later use
they should redirect overflow to infiltrate the soil and replenish the water table. Each installation of
storage gutters and/or tanks requires careful consideration of rainfall patterns and occupant usage
levels compared with the area of roof available for collection and the site area available to disperse the
overflow. In all installations the soil characteristics are tested to determine the absorptive area needed
to cope with the anticipated run-off once the storage gutters are full. A measure of the infiltration level
needed can be calculated in the following manner:
Di = A × S + IA × S
Di is the height of the column of water to be infiltrated by seepage area in metres
A is the roof area in m²
S is the 100 year design storm for the location in m/hr
IA is the seepage or infiltration area available in m²
This yields a column height of water which must be infiltrated . A simple test is then done on
site. An infiltrometer is driven into the soil to a level of at least the height of the column of water
calculated for the location. The infiltrometer consists of a 400 mm plastic pipe with inner galvanized
steel sleeve at the end that penetrates the ground. The pipe contains an inner plastic tank with
four 3 mm small holes in the bottom surface. A light shower of water is delivered from the holes to the
ground. The required volume of water to simulate the amount of rainfall received in one hour of
the 100 year design storm for the area is allowed to fall on the ground surface. A site passes the test if
all the water has been absorbed and there is no visible surface ponding after 24 hours. Since the
storage gutters retain the first flush of any rainfall event there is a considerable built in safety factor in
designing for infiltration areas to be able to cope with the runoff from a design storm of one in one
hundred years intensity. Estimates have been made of the potential displacement that the gutters can
provide in Australian cities based on rainfall averages collected over the pass hundred years. These
figures are shown in Table 1. Of course decreased rainfall due to climate change would lessen the
impact of the gutters and the savings that can be achieved. At the same time, however, decreased
rainfall makes the gains made from any efficiency more significant.
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Table 1. Estimated potential displacement of reticulated water with rainwater from storage
gutters in Australian cities.
Estimated potable water replacement % for
a 200 m² house with average occupancy patterns
(Source: John Argue, Urban Water Resources Centre, University of South Australia).
3. History of Implementation
The success of any new idea in construction is very dependent on achieving the cooperation of
tradesmen and others who work in associated areas and are partially affected by the changes required.
The result of this interdependence is that construction innovations which appear to involve changes to
a single component in the building process often have essential flow over effects on surrounding trade
practice. The management of the interaction between a green building innovation proposed by a
designer and the tradesmen who implement it can become even more important than the value of the
innovative idea itself. Certainly the diffusion of the innovation into general industry practice will not
occur without „winning the argument for change‟ with all the stakeholders. This inertia is an essential
characteristic of craft-based traditional construction, and cannot be ignored if construction is to lift its
environmental performance. An example is presented of the introduction to the Australian residential
construction industry of an innovative system for handling stormwater from roofs. The difficulties
encountered elucidate the process of construction innovation and indicate some of the necessary
conditions for the diffusion of a sustainable building idea.
A study of 23 early installations was made. The early installations of the storage gutters were
carried out by small individual house builders and by a large project home company. Several
difficulties were encountered due to the departure the gutters represented from standard practice.
Table 2 reports on some of the difficulties experienced with the early cases of storage gutter
installations in the late 1990s. Figure 2 illustrates some of the detailing involved in making the
installation work correctly.
Because traditional quad and fascia gutters are laid to a fall of between 1 in 100 and 1 in 20 it is not
essential that the fascia board or the roof edge be strictly level. In fact, fascia boards are usually not
level and this is not apparent with ordinary gutters because the fall in the gutter acts to camouflage
irregularity. Storage gutters, however, need to be laid absolutely level for their full storage capacity to
be achieved. This means that lower tolerances and a higher level of workmanship are required from the
roof framers and roof cladding installers. This was not always immediately apparent when builders
first agreed to fit the storage gutters to houses under construction. This presents an even greater
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difficulty when the gutters are retrofitted to existing houses where the fascia boards and roof edge are
likely to be slightly out of level, resulting in unsightly gaps between the roof edge and the gutter top at
Table 2. Problems experienced with the early delivery of storage gutter innovation.
Problem caused by
Gaps between roof
edge and gutter top
Adjustable brackets to enable the storage
gutters to be laid level around the whole roof.
Advice to builders of the importance of
maintaining level edge around roof.
Gutters leaking at
Internal painted-on waterproofing plus silicon
seal at joints. Roll form rather than fold gutters
for greater accuracy of shape therefore fewer
leaks at mitred joints.
Gutters overflow at
Overflow holes not to be situated at doorways
or projecting windows. Generally downpipes
and spreaders to be preferred to overflow holes.
Water stains on
Drip mould formed in gutter or at edge of eaves
lining. Gutter to be positioned with bottom
surface below the edge of the eaves lining.
Toilet cisterns not
Larger diameter pipes for inlet to toilet cistern
(18 mm no 12 mm). Plumbers are not to use
pipe sizes they would use for mains pressure
Top up valve not
failing to shut off
Cut-off valve to be position along rather than
across the gutter.
Instructional information to be provided for
occupant. Careful positioning of plug for
flushing sludge trap with a garden hose.
Occupant to be made aware of the need for soft
surface areas to absorb run-off. Restrictions on
percentage site areas that can be hard paved.
This is only a problem if the house is
unoccupied for long periods during a drought.
Normally the constant movement of the water
through the system would prevent infestation.
If the house is unoccupied arrangements need
to be made for periodic charging of the system.
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Figure 2. Gutter section showing downpipe and fixing brackets.
This quality issue was dealt with in two ways. Firstly, it was necessary to ensure that builders were
well informed on the system requirements before installation commenced. Indeed it was necessary to
insist that they address the issues, given that some tradesmen appear to operate on the principle of
„when all else fails, read the instructions‟. Secondly, customized gutter brackets were designed which
allowed for accurate adjustment to level during installation.
In the earliest installations, the top lip of the gutter contained perforations which acted as overflow
holes to allow rainfall after the initial storm surge to be returned to the garden. This proved to be
unsuitable in several instances. In reactive soils it is inappropriate to alternately wet and dry out the
soil immediately adjacent to the footings and, indeed, some local government regulations forbade the
practice. In addition, overflow holes over doorways or projecting windows gave unsatisfactory results.
This practice was modified by adding downpipes and spreaders which allowed controlled infiltration
to garden beds (see Figures 2 and 3).
Further issues arose with the plumbers who connected the storage gutters to toilet cisterns or garden
taps. These tradesmen tended to use the same size pipe that they would fit for a mains pressure water
service to the same outlet (even if larger pipes had been specified). However, since the water was
delivered by gravity feed rather than at mains pressure, it was discovered that toilet cisterns took too
long to fill up. They could even run dry at times of high usage which proved to be very unsatisfactory
for the occupants. It was necessary to get the involvement and compliance of the plumbers in selecting
the right capacity pipe for this new installation instead of allowing them to carry on with their standard
practice in the face of new requirements (Figure 4).
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Figure 3. Downpipes and diffusers in landscaped garden area.
Figure 4. Storage gutter serving pipes to toilet cisterns in a community centre retrofit.
Residential construction is essentially a collaborative exercise. The project-based and power-
distributed nature of construction means that innovations often “spill over” beyond the boundaries of
the initial idea . The management of this spill over effect can be the difference between success
and failure for a construction innovation. It has been noted, construction workers have considerable
informal involvement in the delivery of new products and systems and as a result their cooperation is
essential for changed processes to be effectively delivered . Successful technological change in
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construction usually involves an iterative process between designer and practitioner. A good idea will
not be accepted without correspondingly good delivery.
3.1. Occupants’ Experience
Once the construction problems have been ironed out there may still remain difficulties in the
operation of the system by the end user. Environmentally sustainable innovations that involve a
mismatch with the existing system, may be blocked simply because users are not accustomed to the
new innovation . There needs to be a learning and socialization process in the community for the
innovation to be accepted. It is particularly critical that occupants understand the way that the system
works so that they do not modify the landscaping or the gutters themselves in unsuitable ways.
Figure 5. Typical installations in Sydney suburbs.
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Observation of 23 early roof storage gutter installations in one local government area in Sydney has
revealed the difficulties involved in implementing an innovation that involves introducing a
non-standard practice to the general public (see Table 1 and Figure 5). Many householders have little
or no knowledge of basic construction and maintenance issues and they simply expect a new house to
function well without any significant intervention on their part. While this may generally be a not
unreasonable expectation, there are times when a certain amount of ongoing maintenance is critical to
the continued good operation of building services. The occupant needs to have a basic understanding
of how systems work in order that problems are recognized at a stage where they can be easily
corrected. This concept is understood with motor cars and few people would fail to be aware of the
need for a maintenance and adjustment regime to support the proper functioning of their motor vehicle,
however, this need is often not appreciated with a house.
The storage gutters are fitted with leaf-guard to prevent blockage from large quantities of leaf litter
but the design also involves the need for occasional flushing out of fine debris which collects in the
bottom fold of the gutter. Some residents reported considerable annoyance at this task and rejected the
system because of it. The early installations with a full circle of the infiltration holes in the lip of the
gutter also provoked occupant‟s ire because during heavy rain they sent curtains of water down in
front of doorways and projecting or bay windows. This is illustrated in Figure 6.
Figure 6. Curtain of water from overflow holes and splash line on wall.
An example of poor understanding of a new system by an owner/occupier is illustrated below in
Figure 7. Undersized pipes were used to feed to the toilet cistern. When the resident threw a party the
cisterns failed to fill quickly enough at peak usage and the toilet would not flush leading to
embarrassment for the host. Instead of fitting larger inlet pipes, his response was to reconnect the
cistern to the reticulated water service and cut a hole in the storage gutter fitting a pipe leading to a
plastic barrel. The collected water was used to hand water mango trees in the front yard. This was
working successfully during the drought period when it was installed but is likely to result in
considerable flooding problems when heavy rain eventually falls.
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Figure 7. User modification to storage gutters.
Further complaints were expressed about the gutters leaking at the joints, overflows running back
along the face of the gutter resulting in staining of the eaves lining and top up valves failing to cut off.
These complaints amount to simple quality control issues which result from the tradesman installing
the gutters being unfamiliar with the system. They are now being addressed by more stringent
specification of methods and materials to be used, as well as by training of the tradesmen involved by
the gutter supplier. In addition, a training module has been prepared for the trade training course for
roof plumbers, to ensure that future workers will be familiar with the requirements and properties of
the system. The 23 houses observed for this report were all early installations of storage gutters in the
late 1990s. Current installations have largely overcome the problems described through information
programs and better quality control.
Wider use of training packages for tradesmen and handymen who install roof gutters could go a
long way to preventing several of the problems experienced in the cases studied. It is also important
that householders are provided with information about the potential problems so that they know what
to do when they encounter difficulties. Mostly the measures required needed to avoid these problems
involve little or no extra cost. The cost of slightly larger service pipes from the gutters to the toilet
cisterns or washing machines is negligible. Ongoing maintenance of the storage gutters by occasional
flushing of any collected debris is also a negligible cost and something that most householders are able
to carry out as part of their regular maintenance regimes. It is, however, necessary that this is
understood from the start by the occupier of the house with a storage gutter installation. Increasingly,
owner manuals are provided with new houses as they have long been with new cars. This is a way of
ensuring that regular maintenance is carried out and major problems are avoided.
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It is of vital importance that the housing sector in Australia and countries where the conservation of
water is increasingly critical in the face of potential climate change, develop systems for water
efficiency which reduce reliance on new dams and large scale community water supply. Pressure on
existing resources is growing with the rise in suburban affluence, and global warming may threaten
expected rainfall levels in existing catchments. The storage gutter system represents an attempt to
reduce suburban household dependence on piped water supply by using rainwater for some non
potable uses in a systematic way. The system is compatible with, but separate from, grey water reuse.
If the installation is done correctly and if the system is properly maintained it can result in significant
savings in water charges for the householder, reduced infrastructure costs for the community while at
the same time reducing the environmental impact of residential development in areas of moderate or
erratic rainfall. The idea has the potential to make a significant contribution towards a more
sustainable management regime for water resources in suburban areas.
Unfortunately, the process of delivering a new idea to the established residential construction
industry is likely to be fraught with difficulty. This is especially true when the idea or innovation is at
first glance only a minor modification of existing practice. In these circumstances tradesmen tend to
think they need no special instruction or training about something with which they are already familiar.
In the case of storage gutters instances were observed where plumbers chose to ignore instructions
about pipe sizes from the gutter supplier because they believed their standard practice overrode such
instructions. Construction innovations, particularly those with environmental benefits, need to be
carefully explained to all those involved in their delivery or they are likely to fail to meet their goals.
The potential of the human factor to interfere with the achievement of environmental efficiencies
cannot be lightly set aside. In addition, when the construction industry has absorbed the purpose and
potential of the idea, there still remains the end users who need to know how the system works and
how it may be adjusted for their special circumstances. Otherwise they may make inappropriate
adjustments or reject the system out right.
The story of the early implementation of the innovative storage gutter system has lessons for other
ideas which seek to modify housing industry practice in order to achieve more sustainable
development. New ideas need to be carefully tested by the trades who will put them into practice and
their preceding and following trades. Understanding should not be assumed and the idea should have
all its features explicitly explained. In addition, an awareness campaign among end users should be
considered. Failure to take an inclusive approach to the delivery of the innovation is likely to result in
underperformance and unsuccessful diffusion of the system throughout the industry as a whole.
The author would like to thank the Australian Cooperative Research Centre for Construction
Innovation for supporting this research. Frank Smith of Rainsaver Australia Pty Ltd is the inventor
of the system discussed and was very helpful in providing information and access to storage
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