FLOW RESTRICTOR
In the UK, rainwater can be handled either by diverting runoff from buildings into
soakaways underground, into water harvesting tanks or by diverting the runoff directly
into the sewer system.
Due to the age of the UK sewer system, current building regulations in the UK may
include limits on levels of runoff water. For example, one criterion of new construction
projects is that they may not be allowed to increase the rate at which water is
discharged into public sewers compared to the pre-existing site. Thus, the sewers are
protected from spikes in water flow due to new constructions.
These regulations may be met by reducing hard landscaping and promoting natural
drainage, or by providing temporary storage tanks which regulate the flow over a longer
period and thus reduce the peak flow rates. In locations where large tanks are not
possible, one alternative has been to use flat roofs as a temporary storage tank by
limiting the rate of water runoff from the roof. These are commonly known as blue
roofs.
In blue roofs, the roof is designed to be substantially flat and is provided with a number
of outlets connected to the drain, through which the runoff water flows. The outlets may
be designed so that the maximum rate of water leaving the roof is not in excess of the
legal restriction. Since this is usually less than the rate at which the rain fills the blue
roof, the water builds up gradually. Overflow pipes may be provided in order to ensure
that the roof does not become overloaded and prevent any structural damage from the
weight of the water. While the system is effective in regulating flow output from the roof,
it requires careful planning to ensure that the flow rate through the provided outlets is
neither too great, thereby negating the effects of the blue roof, nor too low, and causing
water to build up too quickly and be diverted through the overflow pipes.
A further measure to reduce runoff rate is the use of green roofs, or living roofs, which
are covered with a layer of vegetation over a waterproofing membrane. Commonly this
involves a layer of soil in which grasses, mosses and other plants may be grown, which
absorbs rainwater and provides additional insulation to the building. Green roofs can
also be used in combination with blue roofs, e.g. areas of the roof may be discrete, or
the soil and vegetation layer may be raised from the surface of the roof so that the area
below the green layer may act as a drainage layer or as water store as in a more
conventional blue roof.
UK patent application GB2502515 describes a flow restrictor that can be inserted into a
conventional drain outlet with a narrow channel for limiting the water flow into the drain
system. A range of inserts are provided with varying channel widths. The flow restrictor
is then fitted with an insert with a desired channel width in order to provide a degree of
adaptability to the unit. However, the inserts must either be sold separately, or a range
of inserts must be provided with each unit.
It is an aim of the present invention to provide a flow restrictor which mitigates or
ameliorates at least one of the problems of the prior art, or provides a useful
alternative.
According to a first aspect of the invention there is provided a drain flow restrictor,
comprising:
a body comprising an aperture through the body, through which fluid flows, and
a mounting surface for mounting the flow restrictor on or in a drain outlet; and
a restrictor portion; wherein
said restrictor portion is movable from a first position to a second position in
order to restrict fluid flow through the aperture.
The flow restrictor according to the first aspect allows at least two different rates of fluid
flow without requiring any additional components or parts. In one configuration the
restrictor portion is in the first position and fluid may flow at a first rate. In a second
configuration, the restrictor portion is in the second position and the fluid flow is
restricted to a second rate, less than the first. Thus, two rates of flow are attainable with
a single flow restrictor.
The restrictor portion may restrict fluid flow through the aperture by restricting the size
of the aperture e.g. by blocking or sealing at least part of the aperture. The aperture
defines a flow path through the body through which fluid can travel. In one
embodiment, the restrictor portion reduces the cross-sectional area of the flow path
through the aperture. Cross-sectional area is intended to mean the area in the plane
perpendicular to the flow path. The restrictor portion may be movable through multiple
positions, for example, to provide multiple restriction levels.
The first position may correspond to the position wherein maximum permitted fluid flow
through the aperture is achieved. For example, the first position may comprise the
position wherein the cross-sectional area of the aperture is at a maximum. In one
embodiment, in the first position the restrictor portion may not restrict, or substantially
not restrict the fluid flow. E.g. the restrictor portion is not blocking or sealing the
aperture, or substantially not blocking or sealing the aperture. Alternatively, the first
position may comprise any position wherein the permitted fluid flow rate through the
aperture is greater than the second position. For example, the first position may
comprise any position wherein the cross-sectional area of the fluid path is greater than
in the second position.
The second position may correspond to the position wherein a minimum fluid flow
through the aperture is permitted. In one embodiment, the restrictor portion may
restrict, or substantially restrict all fluid flow through the aperture when in the second
position. E.g. the restrictor portion may block or seal the aperture, or may substantially
block or seal the aperture. Alternatively, the second position may comprise any position
wherein the permitted fluid flow rate through the aperture is lesser than the first
position. For example, the second position may comprise any position wherein the
cross-sectional area of the fluid path is lesser than in the first position.
The flow restrictor may comprise any number of intermediate positions between the
first and second positions. The intermediate positions may allow varying levels of fluid
flow through the aperture. In one embodiment, the intermediate positions may be
continuous from the first to the second position. In one embodiment, the intermediate
positions may comprise a series of defined positions, for example, regularly spaced
between the first and second positions.
The present invention is therefore more adaptable than those known in the prior art. In
some embodiments, the flow restrictor may comprise only two parts. Thus, there are
fewer parts to manufacture and thus manufacturing and shipping costs are reduced.
Furthermore, since there are no interchangeable parts or inserts, there is less wastage
caused by loss of parts or by the necessity to provide multiple redundant inserts with
each unit. The flow restrictor is also more desirable for users, since there is no need to
purchase and install multiple different sizes of flow restrictor and the flow rate may be
adjusted or configured after the flow restrictor has been installed. Instead, they can
purchase multiple copies of a single unit and adjust the flow rates to suit the specific
application. Furthermore, since the flow rate is selected by the position of the restrictor
portion, there is no need for additional parts, inserts or specialist tools.
The flow restrictor may be configured to fit in a conventional drain outlet. For example,
the flow restrictor may be circular. The flow restrictor may comprise an angled or
chamfered surface. In one embodiment, the body is frusto-conical. The angled or
chamfered surface and/or the angled face of the frusto-conical body may be configured
to fit with a similarly angled, chamfered and/or frusto-conical drain outlet. This design is
advantageous since it can be used with varying sizes of drain outlet without requiring
modification.
Additionally or alternatively, the mounting surface may comprise a stepped portion
designed to sit on a cooperating surface of a drain outlet.
In one series of embodiments, the restrictor portion is rotatably movable relative to the
body. For example, the restrictor portion may be rotated from the first position to the
second position. In one embodiment, the restrictor portion may be connected to the
body by way of a pivot means, e.g. a pin or rivet. The restrictor portion may be
rotatable about the pivot means.
In one embodiment, the body may comprise an overflow aperture. The overflow
aperture may be positioned in the centre of the body, e.g. the overflow aperture may
extend from the centre of a first face to the centre of a second face of the body. The
overflow aperture may receive an overflow pipe. The overflow aperture may define an
overflow path through which fluid can pass.
In one series of embodiments, the restrictor portion may comprise a projection received
within and/or extending through the overflow aperture. The projection may abut the
inner surface or edge of the overflow aperture. The projection may be rotatable within
the overflow aperture such that it forms a pivot about which the restrictor portion may
rotate. The first aperture may be arcuate and positioned radially around the overflow
aperture, e.g. the two apertures may be coaxial.
The projection may be cylindrical. The projection may comprise an open first end and a
closed second end, or it may comprise a pair of open ends. The projection may be
configured for provide a form interlock with the body, in order to inhibit the body and
restrictor portion becoming detached. For example, the projection may comprise a
concentric channel in its outer surface for cooperating with a projecting ridge provided
on the inside of the overflow aperture. The concentric channel may be segmented, for
example, to provide an interlock with a different strength to a continuous channel. In
embodiments wherein the projection comprises a closed end, the closed end face may
be provided with a drill location means at the centre thereof.
The projection may be housed within the overflow aperture and receive an overflow
pipe e.g. so as to provide an overflow path through both the projection and the overflow
aperture through which fluid can pass. The closed end of the projection may be
removed by a user, e.g. by drilling through the centre, so as to permit fluid flow through
the projection. The overflow pipe may extend beyond the upper surface of the body
and/or restrictor portion. The length of the overflow pipe may determine the maximum
water level permitted in a blue roof or water attenuation tank.
The flow restrictor may comprise one or more indexing means for indicating the first
and/or second position, and/or any number of intermediary positions. The indexing
means may comprise one or more detents, grooves and a complementary projection or
vice versa, or visual identifiers, for example, to assist the user in setting the desired
level of flow rate through the aperture. For example, the indexing means may comprise
a groove on either of the body or the restrictor portion, and a tooth on the other of the
body or the restrictor portion. The groove may comprise a pair of adjacent ridges with a
groove positioned between. The tooth and groove or grooves may cooperate so as to
interlock e.g. in use, the tooth may be loosely held in the groove so as to restrict
movement of the restrictor portion relative to the body. The indexing means may
provide a level of resistance that can be felt by the user when moving the restrictor
portion, but would not prevent movement beyond the indexing means.
The flow restrictor may further comprise a screw clip and/or a screw hole, e.g. on the
restrictor portion. The screw clip may be configured to hold a screw or bolt. The
restrictor portion may be moved into its desired position and fixed in place by inserting
the screw or bolt through the screw hole and either into or through the body. The screw
clip therefore provides a simple way to ensure that the screw or bolt is not lost during
transit, and is in the right location when the flow restrictor is being positioned.
According to a second aspect of the invention, there is provided a drain flow restrictor
comprising:
a body comprising a plurality of apertures through the body, through which fluid
flows, and a mounting surface for mounting the flow restrictor on or in a drain
outlet; and
one or more restrictor portions; wherein
said restrictor portions can be inserted into said apertures so as to limit fluid
flow therethrough.
In one embodiment, the apertures are all identical in size and shape. In a further series
of embodiments, the apertures may be different sizes. For example, the body may be
provided with one or more first apertures, and one or more second apertures, larger
than the first. The restrictor portions may be more than one size. For example, the
restrictor portions may be configured to fit into either a first, or a second aperture. The
restrictor portions may be colour coded, for example, to indicate variation in size and/or
shape.
By inserting a restrictor portion into the body, the number and/or size of the apertures
may be reduced. For example, the apertures define the fluid path through the drain flow
restrictor, and inserting one or more restrictor portions limits the cross sectional area of
the fluid path through the body. In one embodiment, the restrictor portion may
completely preclude fluid flow through the aperture into which it is inserted.
The restrictor portions may comprise removable inserts. The inserts may comprise a
body and a head portion, wherein the head portion extends beyond the edge of the
aperture into which it is inserted. For example, the inserts may have a T-shaped crosssection,
wherein the head portion abuts the surface of the body. The head portion may
therefore provide a fluid resistant seal. The restrictor portions may comprise a plastic or
rubber material. For example, the restrictor portions may comprise PVC or HDPE.
The restrictor portions may be held in position by an interference fit, frictional fit and/or
snap-fit. For example, the restrictor portion may slot in to the apertures without
requiring any further attaching means. Alternatively, the restrictor portions may
comprise teeth or lugs which clip into a corresponding groove, hole, channel or
depression in the side of the aperture, or vice versa. In one embodiment, the restrictor
portions are held in place by friction with the aperture, e.g. where the restrictor portions
are made from a rubber material. For example, the rubber material may be
compressed slightly upon insertion, so as to ensure a tight seal within the aperture.
The body may comprise a flat surface. The apertures may be regularly spaced around
the body, for example in a repeating pattern. In one embodiment, the apertures are
arranged in concentric rings.
The body may be fully housed within a drain outlet and/or it may comprise an upper
surface of a drain outlet. In one example, the body comprises a roof portion of a drain
outlet.
The drain flow restrictor may comprise an overflow aperture. The overflow aperture
may be configured to receive an overflow pipe, which extends away from the surface of
the body to provide an overflow flow path with an opening positioned, in use, above the
body. The overflow aperture may have a circular cross section, for example for
receiving a cylindrical overflow pipe.
The drain flow restrictor may comprise a combination of apertures and restrictors
according to the first and second aspects of the invention.
According to a third aspect of the invention, there is provided a drain outlet comprising
the flow restrictor according to the first and/or second aspect of the invention.
The drain outlet may comprise an outlet body with a pair of open ends, a connecting
portion adjacent the smaller of the open ends for connecting to a drain or pipe and a
mounting surface for receiving the mounting surface of the flow restrictor. The
mounting surface may be frusto-conical and/or it may comprise a stepped portion,
depending on the mounting surface of flow restrictor. The drain outlet may be frustoconical
so as to funnel water towards the connecting portion.
In one embodiment, the drain outlet may further comprise a flat roof portion. The flat
roof portion may sit within the outlet body and comprise a flat surface in substantially
the same plane as the uppermost open end of the outlet body. The flat roof portion may
comprise a series of holes or channels to act as a filter so that water may flow through
the roof portion but prevent solid objects from entering the outlet body. The flat roof
portion may be strong enough to hold the weight of a person standing on the outlet
roof. In one embodiment, the roof portion may comprise a drain flow restrictor
according the second aspect of the invention.
In an alternative embodiment, the drain outlet may further comprise a domed roof
portion. The domed roof portion may extend beyond the uppermost open end of the
outlet body. The domed roof portion may comprise a series of holes or channels so as
to act as a filter and prevent solid objects from entering the outlet body. The domed
roof portion may be curved, for example a hemi-sphere, spherical segment, or irregular
curve. Alternatively, the domed roof portion may be cylindrical, conical or frusto-conical.
The drain outlet may further comprise an overflow pipe. For example, the drain outlet
may comprise a pipe received within a projection and/or overflow aperture on the flow
restrictor. The overflow pipe may extend from the uppermost surface of the flow
restrictor and/or the uppermost surface of the outlet body. In one embodiment, the
drain outlet comprises a domed roof portion and an overflow pipe, wherein the overflow
pipe is housed within the domed roof portion. The overflow pipe may extend a distance
corresponding to the maximum depth of water permitted on a blue roof, green roof
and/or a water attenuation tank.
In use, the drain outlet is installed and the flow restrictor is set to permit the desired
flow rate through the outlet by moving the restrictor portion to the desired position
relative to the body. When it rains, the water flows through into the drain outlet and
through the aperture into the drain system. During heavy rainfall, the rate at which
water flows through the aperture may be less than the rate at which the blue roof,
green roof or water attenuation tank fills. Thus, the depth of water above the flow
restrictor slowly increases. In embodiments where an overflow pipe is installed, when
the water level exceeds the height of the overflow pipe, the water flows through the
overflow pipe and through an overflow aperture in addition to flowing through the first
aperture. Thus the flow rate through the flow restrictor is increased.
According to a fourth aspect of the invention, there is provided a drainage system
comprising at least one drain outlet according to the third aspect of the invention.
The drainage system may comprise a blue roof, green roof, water attenuation tank
and/or any other suitable form of water attenuator or combination thereof, at least one
drain outlet according to the third aspect of the invention, and at least one pipe
connecting the drain outlet to a municipal drain or soakaway.
In one series of embodiments, multiple drain outlets according to the second aspect on
the invention are provided. The flow restrictors may be configured to permit varying
flow rates. Additionally or alternatively, one or more of the multiple drain outlets may
comprise overflow pipes. In embodiments with more than one overflow pipe, the flow
rates through the overflow pipes may be different depending on the diameter of the
pipe and/or the diameter of the second aperture. For example, holes drilled through the
closed end of the projection may vary in size depending on the desired flow rate
through the overflow pipe.
The overflow pipes may be of varying length so as to permit fluid flow through a first
overflow pipe prior to permitting fluid flow through a second overflow pipe. The overflow
pipes may be configured to provide a gradual increase in capacity (i.e. flow rate) as the
depth of water on the blue roof, green roof and/or in a water attenuation tank increases.
This may be advantageous where the first overflow pipe is configured to permit water
flow prior to the maximum water level being reached. This may allow water to flow at
an increased rate, but still below the rate at which water fills the tank, so as to reduce
the rate at which the tank fills.
Embodiments of the present invention will now be described by way of example and
with reference to the accompanying figures, in which:
Figure 1 is a perspective drawing of the flow restrictor according to the first aspect;
Figure 2 is a plan view from above showing the flow restrictor in the first position;
Figure 3 is 2 is a plan view from above showing the flow restrictor in the second
position;
Figure 4 is a section through the line X-X;
Figure 5 is a plan view from above showing a drain outlet according to the third aspect
of the invention;
Figure 6 is a section through the line Y-Y;
Figure 7 is a section through the line Y-Y of an alternative embodiment of the third
aspect;
Figure 8 is a perspective drawing of a flow restrictor according to the second aspect of
the invention;
Figure 9 is a section through the line Z-Z of Figure 8 ; and
Figure 10 is a perspective view showing a further embodiment of the first aspect of the
invention.
Turning now to Figure 1, there is shown an embodiment of the flow restrictor according
to a first aspect of the invention. The flow restrictor 1 has a body 2 with an aperture 3
extending therethrough and a restrictor portion 4 on the upper surface of the body 2 .
The body 2 is disc shaped with an angled surface, with a series of indentations 5 in its
outer edge in order to fit around screw holes in a drain outlet (not shown). The angled
surface of the body 2 forms the mounting surface 6 .
The body 2 comprises a second aperture 7 in the centre thereof, through which a
cylindrical projection 8 extends and is held. The cylindrical projection 8 is part of the
restrictor portion 4 , and acts as a pivot around which the restrictor portion 4 can rotate.
Depending on the direction of rotation of the restrictor portion 4 , the first aperture 3 is
progressively covered or exposed so as to increase its surface area and thereby adjust
the flow rate of water through the aperture 3 .
The facing surfaces of the body 2 and restrictor portion are provided with a series of
indexing means 9 arranged at regular intervals around its outside edge. The indexing
means 9 comprise a pair of teeth with ramps 9a on either side and a groove 9b in
between. The restrictor portion 4 has a tab 10 extending radially outwardly so that, as
the restrictor portion 4 rotates, only the tab 10 passes over the indexing means 9 . The
surface of the tab 10 facing the body has an additional tooth (not shown) which
interacts with the indexing means 9 by riding up the ramps 9a to sit in the groove 9b.
This provides an easy mechanism by which defined positions for the restrictor portion 4
may be located by a user, and which are easily visible and/or felt. The upper surface of
the body 2 also has a ridge 14 running concentrically with the restrictor portion 4 . The
ridge 14 serves two purposes: firstly, by running concentrically with the restrictor
portion it provides a seal where the two parts abut so as to prevent water from running
around the restrictor portion; and secondly, it provides a hard stop preventing the over
rotation of the restrictor portion 4 by abutting the tab 10 when the restrictor portion 4 is
in the first position A and the second position B.
The restrictor portion 4 is also provided with a screw holder 11, screw 12 and screw
hole 13. When the user has rotated the restrictor portion 4 to the desired position, the
screw 12 may be removed from the holder 11 and screwed through the screw hole 13
into the body 2 . The restrictor portion 4 is thus locked in position relative to the body 2
so that it cannot become accidentally dislodged during operation (for example by a
piece of debris etc.) and change the flow rate through the flow restrictor 1. If the user
wishes the change the flow rate for any reason, they can simply unscrew the screw 12,
rotate the restrictor portion 4 to a new position, and then re-insert the screw 12 through
the screw hole 13 into a new part of the body 2 . When the body is produced from
plastic, for example HDPE, PVC or similar, the screw may be screwed directly into the
body without requiring a screw hole to be pre-drilled. In embodiments made from
stronger materials, such as aluminium, screw holes may be required to be drilled by the
user, or even pre-drilled during manufacture, adjacent each indexing means.
Alternatively, the screw may be replaced with a bolt and can thus be bolted in place.
Holes running through the body would be too small to affect the flow rate running
through the flow restrictor.
Turning now to Figure 2 , the restrictor portion 4 is shown in the first position A. The
restrictor portion 4 is fully rotated (i.e. further rotation is prevented by the ridge 14) to
give the aperture 3 the largest attainable cross-sectional area. This corresponds with
the greatest flow rate through the aperture 3 . The tab 10 is abutting a first end 14A of
the ridge 14.
Turning now to Figure 3 , the restrictor portion 4 is shown in the second position B. The
restrictor portion 4 is fully rotated in the opposite direction to that shown in Figure 2 , so
as to restrict flow through the majority of the aperture 3 . The tab 10 is abutting a
second end 14B of the ridge 14. In this embodiment, when the restrictor portion 4 is in
the second position B, the aperture 3 is not fully obstructed, and thus a small area is
still exposed. Due to the size of the exposed aperture 3 , the flow rate in the second
position B is very low and is the minimum flow rate.
Referring now to figures 2 and 3 , the projection 8 also has a drill guide 15 in the centre
of the base of the projection 8 . If a user wishes to fit an overflow pipe to the flow
restrictor 1, the user drills out the base of the projection 8 and inserts the overflow pipe
into the projection (see Figure 7). The overflow pipe provides an alternative flow path
for water to flow though the projection 8 and thus through the second aperture 7 .
Turning now to Figure 4 , the flow restrictor 1 is shown in cross-section through the line
X-X of Figure 3 . More clearly shown is the frusto-conical shape of the body 2 , with the
mounting surface 6 formed by the angled surface. In use, the flow restrictor 1 can be
simply placed in a drain outlet (not shown) if the angle of the restrictor 1 matches that
of the outlet. In applications with drain outlets of differing angle or shape (for example,
if retrofitting a roof to act as a blue roof) the flow restrictor may sit within an adaptor or
spacer (not shown).
Also shown is the interlock joining the body 2 and the restrictor portion 4 . The body 2
has a lip 16 running around the internal face of the second aperture 7 . The lip 16 fits
within a groove formed between a corresponding ridge 17 of the projection 8 and the
upper surface 18 of the restrictor portion 4 , which extends over the body around the
circumference of the second aperture. To connect the body 2 and the restrictor portion
4 , the projection 8 is inserted through the second aperture 7 until the lip 16 on the body
rides over the corresponding ridge 17 on the projection and sits in the groove formed
between the ridge 17 and the upper surface 18 to form an interlock. To disconnect the
body and the restrictor portion, the resistance caused by the ridge must be overcome,
thereby providing a strong connection between the two components. Since the
interlocking parts are both circular, it permits them to rotate relative to one another
while remaining sealed i.e. to allow the restrictor portion 4 to rotate about the second
aperture 7 and adjustably block off the first aperture 3 .
Turning now to Figures 5 to 6 , there is shown a drain outlet according to an
embodiment of the invention.
The drain outlet 20 is made up of a frusto-conical outlet body 2 1 with an open upper
end 22 and lower end 23. The lower end terminates in a connecting portion 24 which
can be attached to a drain pipe or similar. The internal face of the frusto conical body
2 1 forms a mounting surface 25 on which a flow restrictor 1 is housed. Above the flow
restrictor, a flat roof portion 26 is housed within the outlet body 21. The flat roof portion
26 has a flat upper surface 27 and a mounting surface 28 for mounting onto the inner
surface of the outlet body. Flat roof portion 26 also has a series of screw holes 29 into
which screws 30 can be inserted to securely hold the roof portion 26 to the outlet body
2 1 and sandwich the flow restrictor 1 in between. The open upper end 22 of the body
2 1 extends into flange portion 29 which are provided with further screw holes 34. The
flange extends around the circumference of the outlet body 2 1 so as to connect the
outlet to the surface of a blue roof or attenuation tank (not shown).
Figure 7 shows an alternative embodiment of the third aspect, wherein like parts will
not be further described. The flat roof portion 26 shown in Figure 5 and 6 has been
replaced with a domed roof portion 32, which extends upwardly from the upper surface
of the outlet body 2 1. Both domed roof portion 32 and flat roof portion 26 are provided
with multiple holes and slits 3 1 through which water can flow but which act as a crude
filter to prevent large objects blocking the flow restrictor. Both roof portions 26, 32
protect the flow restrictor from adjustment or accidental damage.
The extra height of the domed roof portion 32 means there is a larger gap between the
uppermost surface of the flow restrictor 1 and the inside of the roof. Thus this design
permits the use of an overflow pipe 33 which is housed within the projection 8 . The
base of the projection 8 has been removed in order to permit water to flow through the
overflow pipe 33 and thus through the second aperture 7 . The overflow pipe 33
extends beyond the uppermost surface of the body 2 1 by height H. The height H can
be varied by using longer or short overflow pipes. The greater the height H, the greater
the depth of water that can build up on the blue roof or tank. Thus the height H
provides a control to prevent the maximum weight on the roof being exceeded, for
example, if the first aperture becomes blocked or if the rainfall is exceedingly heavy.
Turning now to Figures 8 and 9 , there is shown an exemplary embodiment of the flow
restrictor according to the second and third aspects of the invention.
The drain flow restrictor 50 has a body 5 1, through which multiple apertures 52, 53
extend. The apertures 52, 53 are arranged in concentric rings, with first apertures 53
arranged in the inner circle and the second, larger apertures arranged in an outer ring.
There are six first apertures 52 and six second apertures 53 in total, although this may
vary according to requirement. It is envisaged that further sizes of aperture could be
provided, for example in an additional outer circle, for situations where larger flow rates
are required and larger drain outlets available.
The apertures 52, 53 are arcuate, with approximately square ends. This arrangement
allows for close packing of the apertures 52, 53, without compromising the strength of
the upper surface.
Selected apertures 52, 53 are provided with restrictor portions 54, 55, which slot into
the aperture. The restrictor portions are inserts 54, 55 produced from a flexible rubber
compound so that they may be compressed slightly upon insertion to provide a strong
frictional fit within the apertures. The first inserts 54 are of a suitable size to prevent
fluid flow through first apertures 52, and second inserts 55 are of a suitable size to
prevent fluid flow through second apertures 53. In an alternative embodiment (not
shown) the restrictor portions 54, 55 are produced from a plastics material such as
PVC or HDPE and provided with one or more protruding lugs for providing a 'snap-fit'
within a corresponding formation within the apertures 52, 53. The snap-fit may be
sufficient to prevent the restrictor portions being removed from the apertures 52, 53.
The body 50 is also provided with an overflow aperture 58 in the centre of the body 5 1.
In the overflow aperture 58, is provided a pipe holder 59 and an overflow pipe 60. The
pipe holder 59 is provided with a similar lip and groove arrangement 16, 17, 18 as the
rotating restrictor portion 4 shown in Figure 4 . The inner surface of the pipe holder 59 is
cylindrical in order to hold an overflow pipe 60 in a friction fit. The overflow pipe 60
extends above the uppermost surface by a pre-selected distance corresponding with a
predetermined acceptable depth of water.
In this embodiment, the body 50 forms the roof portion of a drain outlet 70 with a body
21A, wherein like parts have not been further described. The body 50 is also provided
with a series of screw holes 56 through which screws 57 are inserted to connect the
body 50 to the drain outlet body 21A.
In use, when a blue or green roof or a water attenuation tank is installed, the installer is
able to fit the drain outlet 70 and then adjust the flow rate through the drain outlet 70 by
selectively inserting inserts 54, 55 into the apertures 52, 53. Where a high flow rate is
desired, fewer of the apertures 52, 53 will be blocked with inserts 54, 55.
It is also possible for the inserts 54, 55 to be used in combination with the drain outlet
pictured in Figures 5 and 6 , since the holes in the roof portion are designed to be the
same size. The whole system is therefore highly adaptable and may be configured to
suit many applications.
Turning now to Figure 10, there is shown a further embodiment of the first aspect of the
invention. The flow restrictor 1A is largely similar to the flow restrictor 1 as shown in
Figures 1 to 4 , and has a body 2A with a restrictor portion 4A rotatably mounted
thereto. The difference between flow restrictor 1 and flow restrictor 1A lies in the
interlock between the cylindrical projection 8A and the upper surface 18A.
Rather than the continuous upper surface 18 shown in Figure 1, the cylindrical
projection 8A is surrounded by segmented region 19A, which extends around the
perimeter of the cylindrical projection 8A and joins the upper surface 18A. The
segmented region 19A is formed of connection segments 71, which have a crosssection
identical to that shown in Figure 4 to provide a snap fit as described above.
Alternately spaced between connection segments 7 1 are spacers 72. Spacers 72 are
apertures in the upper surface 18A, which do not provide a snap-fit arrangement. There
is a ridge (not shown) which runs around the cylindrical projection, similar to the ridge
17 of Figure 4 . The ridge may be continuous, like the ridge 17, or optionally it may also
be segmented.
By providing a segmented region 19A, the strength of the snap-fit connection between
body 2A and restrictor portion 4A can be configured depending on the number and
relative area of the connection segments 7 1 and spacers 72, without affecting the
ability to rotate the body 2A and restrictor portion 4A relative to one another.

CLAIMS:
1. A drain flow restrictor, comprising:
a body comprising an aperture through the body, through which fluid flows, and a
mounting surface for mounting the flow restrictor on or in a drain outlet; and
a restrictor portion; wherein
said restrictor portion is movable from a first position to a second position in order to
restrict fluid flow through the aperture.
2 . The drain flow restrictor according to claim 1, wherein in a first configuration the
restrictor portion is in the first position and fluid flows at a first rate and in a second
configuration the restrictor portion is in the second position and the fluid flow is
restricted to a second rate, less than the first.
3 . The drain flow restrictor according to any one of the preceding claims wherein
the first position corresponds to the position wherein maximum permitted fluid flow
through the aperture is achieved.
4 . The drain flow restrictor according to claim 3 wherein the first position
comprises the position wherein the cross-sectional area of the aperture is at a
maximum.
5 . The drain flow restrictor according to any one of the preceding claims wherein
the second position corresponds to the position wherein a minimum fluid flow through
the aperture is permitted.
6 . The drain flow restrictor according to any one of the preceding claims, wherein
the flow restrictor comprises at least one intermediate position between the first and
second positions.
7 . The drain flow restrictor according to claim 6 , comprising a plurality of
intermediate positions, wherein said intermediate positions are regularly spaced
between the first and second positions.
8 . The drain flow restrictor according to claim 6 , comprising a plurality of
intermediate positions, wherein said intermediate positions extend continuously from
the first to the second position.
9 . The drain flow restrictor according to any one of the preceding claims, wherein
the flow restrictor comprises only two parts.
10. The drain flow restrictor according to any one of the preceding claims, wherein
the mounting surface comprises an angled or chamfered surface.
11. The drain flow restrictor according to any one of the preceding claims, wherein
the restrictor portion is rotatably movable relative to the body.
12. The drain flow restrictor according to claim 11, wherein the restrictor portion is
connected to the body by way of a pivot means and said restrictor portion is rotatable
about the pivot means.
13. The drain flow restrictor according to any one of the preceding claims, further
comprising an overflow aperture.
14. The drain flow restrictor according to claim 13, wherein the overflow aperture
extends from the centre of a first face to the centre of a second face of the body.
15. The drain flow restrictor according to either claim 13 or claim 14, wherein the
first aperture is arcuate and positioned radially around the overflow aperture.
16. The drain flow restrictor according to any one of claims 13 to 15, wherein the
restrictor portion comprises a projection received within and/or extending through the
overflow aperture.
17. The drain flow restrictor according to claim 16, wherein the projection is
rotatable within the overflow aperture such that it forms a pivot about which the
restrictor portion may rotate.
18. The drain flow restrictor according to either claim 16 or 17, wherein the
projection is configured to provide a form interlock with the body, in order to inhibit the
body and restrictor portion becoming detached.
19. The drain flow restrictor according to claim 18, wherein the projection comprises
a concentric channel in its outer surface for cooperating with a projecting ridge
provided on the inside of the overflow aperture.
20. The drain flow restrictor according to claim 19, wherein the concentric channel
is segmented.
2 1. The drain flow restrictor according to any one of claims 16 to 20, wherein the
projection comprises a closed end face, and said closed end face comprises a drill
location means at the centre thereof.
22. The drain flow restrictor according to any one of the preceding claims,
comprising one or more indexing means for indicating the first and/or second position,
and/or any number of intermediary positions.
23. The drain flow restrictor according to claim 22, wherein the indexing means
comprises one or more detents, grooves and a complementary projection or vice versa,
or visual identifiers.
24. The drain flow restrictor according to any one of the preceding claims,
comprising a screw clip and/or a screw hole.
25. A drain flow restrictor, comprising:
a body comprising a plurality of apertures through the body, through which fluid
flows, and a mounting surface for mounting the flow restrictor on or in a drain
outlet; and
one or more restrictor portions; wherein
said restrictor portions can be inserted into said apertures so as to limit fluid
flow therethrough.
26. The drain flow restrictor according to claim 25, wherein the body comprises one
or more first apertures, and one or more second apertures, larger than the first.
27. The drain flow restrictor according to either claim 25 or 26, wherein the
restrictor portions are colour coded to indicate variation in size and/or shape.
28. The drain flow restrictor according to any one of claims 25 to 27, further
comprising an overflow aperture and an overflow pipe received within said overflow
aperture, wherein said overflow pipe extends from the surface of the body.
29. The drain flow restrictor according to any one of claims 25 to 27, wherein the
body also forms a roof portion of a drain outlet.
30. A drain outlet comprising a flow restrictor according to any one of the preceding
claims.
3 1. A drain outlet according to claim 30, comprising an outlet body with a pair of
open ends, a connecting portion adjacent the smaller of the open ends for connecting
to a drain or pipe and a mounting surface for receiving the mounting surface of the flow
restrictor.
32. The drain outlet according to either claim 30 or 31, further comprising a flat roof
portion.
33. The drain outlet according to either claim 30 or 3 1, further comprising a domed
roof portion.
34. The drain outlet according to any one of claims 30 to 33, comprising an
overflow pipe.
35. A drainage system comprising at least one drain outlet according to any one of
claims 30 to 34.
36. The drainage system according to claim 35, comprising a water attenuation
tank and/or a blue roof, at least one drain outlet according to any one of claims 30 to
34, and at least one pipe connecting the drain outlet to a municipal drain or soakaway.
37. A drain flow restrictor substantially as described herein and with reference to
the accompanying drawings.