Patent Publication Number: US-2013248016-A1

Title: Apparatus for the collection of rainwater from a downpipe

Description:
RELATED APPLICATIONS 
     This application is the national stage entry of, and claims priority to, UK patent application serial number GB 1204979.7, titled “Apparatus for the collection of rainwater from a downpipe”, and filed on Mar. 21, 2012, the entire specification of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to water collection generally, and more particularly to collection of rainwater from building runoff. 
     2. Discussion of the State of the Art 
     Getting the rainwater from the roof on which it falls into a suitable holding tank can be achieved simply by placing a tank (also known as a “water butt” or, in the United States, a “rain barrel”) under the open end of a downpipe (or “downspout”) connected directly or indirectly to the guttering around the roof. Water simply flows down the pipe and into the barrel. 
     However, there are a number of disadvantages to this approach. The location of the downpipe may not be a suitable site for a water butt. There may be several downpipes, each of which only catches a portion of the water required. Fitting the water butt under the downpipe often entails cutting off the lower portion of the downpipe. This requires tools, time and discourages temporary use of the pipe—especially in cases where the person that wants to collect the water is not the owner of the property or only wants a temporary solution. Someone renting a barn or stabling their horse at someone else&#39;s yard may not be allowed to cut a pipe in this way. There is also an issue with the overflow from the barrel. Ideally this should be piped back to the drain under the downpipe through which the water would have run away had the water butt not been installed. This can be tricky as the water butt itself may now be blocking the drain. 
     Hence “rainwater diverter” devices have been invented to intercept the water within the downpipe and divert it to the water butt which can then be placed to one side of the downpipe. These typically require that the downpipe is cut and the diverter inserted at the same height as the upper inlet to the water butt i.e. at the maximum height to which the water butt will fill. Such devices normally take advantage of the fact that most of the water flows down the outside of the downpipe rather than through its centre. By trapping the falling water in an annular ring with a lip of perhaps an inch in height, the water caught within that ring will flow out of a collection pipe in communication with the annular chamber thus formed and into the water butt at the other end of the collection pipe. Should the water butt fill to the level of the chamber, the water will no longer flow away to the water butt but will rise within the chamber until it overflows—with the excess water flowing down through the open centre of the device and on down through the pipe. 
     Although such devices avoid the need to remove the bottom section of the pipe, they still require the pipe to be cut. This is particularly problematic in cast metal pipes. Furthermore, if the water butt is subsequently removed, the outlet from the diverter must be blocked or the device removed and the two sections of pipe rejoined. Furthermore, the relatively small collection chamber accumulates debris washed down the sides of the pipe. The small outlet to the collection pipe clogs up easily due to leaves and other debris accumulating therein. Also, the height at which the diverter is fitted must match the fill level of the water butt or the overflow mechanism will not work. This level cannot easily be adjusted once the pipe has been cut and the device inserted. So, for example, replacing the water butt with a larger, deeper one is not an option. Furthermore, the collector typically only fits downpipes of a certain size. 
     The problem of dust and other debris collecting within water butts is itself a major problem. Several different approaches can be taken to achieve a “first flush filter”. When rain starts, the accumulated debris on the roof and in the gutters is washed downwards. The first few litres of water coming down the pipe in each shower contain a high proportion of this debris and are best not collected. A range of mechanisms have been designed to ensure that the initial few litres of water are diverted away from the collecting barrel. These include tilting gutter mechanisms and containers with floating ball valves that collect the water until full at which point the ball rises to the top, shutting them off and diverting the subsequent water to the water butt. A small diameter outlet hole is often provided to allow their contents to dribble slowly away, thus “resetting” them before the next shower. However, such devices also tend to collect debris—unsurprisingly—and need to be cleaned out regularly. They also tend to take up more space, are rarely elegant additions to the outside of any property and typically must be fitted in addition to the diverter mechanism rather than being an integral part of it. 
     There is therefore a need for a non-destructive, hidden mechanism for the collection of water from downpipes. This would not force the water butt to be sited next to any particular downpipe. It would allow multiple downpipes to feed a single water butt and, conversely, one downpipe to feed several water butts—or any number of pipes to feed any number of water butts. It would not collect the first few litres in each shower. It would avoid the accumulation of debris. It would ensure that any overflow continued down the original route the water would have taken prior to the device being fitted. It would be fitted and adjustable without the need for tools and without damage to the downpipe. The invention described here achieves these goals by exploiting the fact that the downpipe itself is normally substantially watertight and can act as the first flush collector. 
     SUMMARY OF THE INVENTION 
     The invention is an apparatus that facilitates the collection of rainwater flowing through a substantially vertical pipe such as a downspout from the eaves of a house. The bottom of the pipe is substantially sealed so that a column of water accumulates in the pipe when it rains. A perforated inner pipe, fed up from the bottom of the downpipe, through said seal, allows this water to flow into a holding tank such as a rain barrel. 
     In many parts of the world, water is scarce and becoming scarcer. Collection of rainwater is a valuable backup or alternative to mains water supply. However, adding rainwater collection to an existing building is sufficiently problematic that this valuable and free resource is often allowed to go to waste. 
     The invention exploits the fact that most rainwater downpipes are themselves hollow, watertight tubes that, if plugged or sealed at the bottom end, could hold a vertical column of water at least to the overflow level of a connected water butt. The apparatus consists of a bung or boot that can be affixed to the bottom of an existing downpipe without having to cut or damage the downpipe. Nor does this require significant space below the bottom of the downpipe. One or more ducts pass through this end seal and project upwards into the existing downpipe so as to allow water to be collected from a predetermined height within the watertight chamber thus formed from the bung or boot and the existing downpipe&#39;s walls. 
     A water collection pipe of diameter significantly less than that of the downpipe itself is inserted up from the bottom of the downpipe and extends up the inside of the downpipe. The upper face of this collection pipe is sealed so that water does not pour into its end. The wall of the collection pipe is perforated for several centimeters beneath the sealed end so that water can flow into it from the sides as and when the downpipe fills with water to that level. The other end of this collection pipe is connected (typically) to the bottom of the water butt allowing the water to flow from the downpipe to the water butt until the levels equalize. 
     Preferably, an overflow mechanism is also provided such that if the water level inside the downpipe exceeds the height to which the water butt can safely be filled, any excess water overflows down the drain above which the downpipe is sited. This mechanism can take a number of forms—such as a float lifting a flapper-valve or a second, “overflow” pipe inserted into the downpipe. The overflow pipe is watertight up to the overflow level but allows water to enter at or above this level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The accompanying drawings illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention according to the embodiments. One skilled in the art will recognize that the particular embodiments illustrated in the drawings are merely exemplary, and are not intended to limit the scope of the present invention. 
         FIG. 1  shows an example of the apparatus using a float activated overflow valve installed in a downpipe and connected to a water butt. 
         FIG. 2  shows detail of exemplary perforations towards the upper end of the collection pipe of  FIG. 1 . 
         FIG. 3  shows an alternative implementation with no moving parts, using a second tube to achieve the overflow mechanism. 
         FIG. 4  shows a plan view of the flexible rubber or silicone bung used in the apparatus of  FIG. 3 . 
         FIG. 5  shows a variant of the apparatus of  FIG. 3  in which a single tube with an internal dividing wall is used for both overflow and collection of water. 
         FIG. 6  shows how the apparatus of  FIG. 3  can be constructed as an integral part of a downpipe section as an alternative to adding it to an existing downpipe. 
         FIG. 7  shows a horizontal cross-section of the downpipe of  FIG. 6 , a few centimeters above the base of the downpipe. 
     
    
    
     DETAILED DESCRIPTION 
     The inventor has conceived, and reduced to practice, an apparatus for the collection of rainwater from a downpipe that addresses the challenges and problems in the art outlined above. Various techniques will now be described in detail with reference to a few example embodiments thereof, as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. However, it will be apparent to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not obscure some of the aspects and/or features described or reference herein. 
     One or more different inventions may be described in the present application. Further, for one or more of the inventions described herein, numerous alternative embodiments may be described; it should be understood that these are presented for illustrative purposes only. The described embodiments are not intended to be limiting in any sense. One or more of the inventions may be widely applicable to numerous embodiments, as is readily apparent from the disclosure. In general, embodiments are described in sufficient detail to enable those skilled in the art to practice one or more of the inventions, and it is to be understood that other embodiments may be utilized and that structural, logical, software, electrical and other changes may be made without departing from the scope of the particular inventions. Accordingly, those skilled in the art will recognize that one or more of the inventions may be practiced with various modifications and alterations. Particular features of one or more of the inventions may be described with reference to one or more particular embodiments or figures that form a part of the present disclosure, and in which are shown, by way of illustration, specific embodiments of one or more of the inventions. It should be understood, however, that such features are not limited to usage in the one or more particular embodiments or figures with reference to which they are described. The present disclosure is neither a literal description of all embodiments of one or more of the inventions nor a listing of features of one or more of the inventions that must be present in all embodiments. 
     Headings of sections provided in this patent application and the title of this patent application are for convenience only, and are not to be taken as limiting the disclosure in any way. 
     A description of an embodiment with several components in communication with each other does not imply that all such components are required. To the contrary, a variety of optional components may be described to illustrate a wide variety of possible embodiments of one or more of the inventions and in order to more fully illustrate one or more aspects of the inventions. Similarly, although process steps, method steps, algorithms or the like may be described in a sequential order, such processes, methods and algorithms may generally be configured to work in alternate orders, unless specifically stated to the contrary. In other words, any sequence or order of steps that may be described in this patent application does not, in and of itself, indicate a requirement that the steps be performed in that order. The steps of described processes may be performed in any order practical. Further, some steps may be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Moreover, the illustration of a process by its depiction in a drawing does not imply that the illustrated process is exclusive of other variations and modifications thereto, does not imply that the illustrated process or any of its steps are necessary to one or more of the invention(s), and does not imply that the illustrated process is preferred. Also, steps are generally described once per embodiment, but this does not mean they must occur once, or that they may only occur once each time a process, method, or algorithm is carried out or executed. Some steps may be omitted in some embodiments or some occurrences, or some steps may be executed more than once in a given embodiment or occurrence. 
     When a single device or article is described, it will be readily apparent that more than one device or article may be used in place of a single device or article. Similarly, where more than one device or article is described, it will be readily apparent that a single device or article may be used in place of the more than one device or article. 
     The functionality or the features of a device may be alternatively embodied by one or more other devices that are not explicitly described as having such functionality or features. Thus, other embodiments of one or more of the inventions need not include the device itself. 
     Techniques and mechanisms described or referenced herein will sometimes be described in singular form for clarity. However, it should be noted that particular embodiments include multiple iterations of a technique or multiple instantiations of a mechanism unless noted otherwise. Process descriptions or blocks in figures should be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process. Alternate implementations are included within the scope of embodiments of the present invention in which, for example, functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those having ordinary skill in the art. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Several variants of the invention are described by way of example. It will be obvious to one of skill in the art that there are many other ways to achieve the features described. 
       FIGS. 1 ,  2 ,  3  and  5  show different examples of the invention inserted into a lower end of a substantially vertical downpipe ( 1 ). A cross-section through only the lower two meters or so of downpipe ( 1 ) is shown. The downpipe ( 1 ) typically extends for at least a further one meter to the eaves of a building where it joins the guttering. The open, lower end of the downpipe may be horizontal (as in  FIG. 1 ) or bent through an angle, typically of fort-five or ninety degrees (so as to direct water away from the wall to which it is typically affixed). 
     Prior to the installation of the apparatus, water flows down from the roof, through downpipe ( 1 ) and into drain ( 3 ) beneath it. 
     Following the installation of the invention, a transfer pipe ( 4 ) may connect the invention to a water butt, rain barrel, or any other watertight container ( 5 ) that is to be filled with said rainwater. Transfer pipe ( 4 ) is typically thin-walled, very flexible and connected at or near ground level to the apparatus and to container ( 5 ). It does not matter that the center of the pipe rests on the ground even though the ends are often connected a few centimetres above ground level. Transfer pipe ( 4 ) may be contiguous with a collection pipe (described later) or may be joined to the collection pipe via any suitable connector. This detail is not shown in the diagrams. 
     Optionally, transfer pipe ( 4 ) does not connect directly to water butt ( 5 ) but, rather, passes through a low level inlet ( 9 ) via a watertight seal, joint or connector and is terminated in a non-return valve ( 10 ) such as a duck-bill valve inside water butt ( 5 ). Valve ( 10 ) allows water to flow into container ( 5 ) when the water pressure in transfer pipe ( 4 ) exceeds that outside valve ( 10 ) but blocks the flow of water in the opposite direction, even if transfer pipe ( 4 ) is empty of water. 
     The valve may be a simple flapper valve or a duck-bill valve made of a very pliable material, such as low-density polyethylene (LDPE) so as to present very little resistance to water flowing into the butt. This component ( 10 )—or some other type of non-return valve is needed only in cases where the apparatus is not completely watertight (as discussed later), and where transfer pipe ( 4 ) enters water butt ( 5 ) below overflow level ( 6 ). 
     Alternatively, transfer pipe ( 4 ) may enter water butt ( 5 ) through a higher-level inlet ( 7 ) at or above overflow level ( 6 ). In this case, water will only start to flow into water butt ( 5 ) when the water column retained in downpipe ( 1 ) reaches this level ( 6 ). Optionally, in this case, transfer pipe ( 4 ) may continue inside water butt ( 5 ) such that its open end is close to the bottom of water butt ( 5 ). This arrangement allows more water to be collected as, once flow has started, the resultant siphon action will drain the bulk of the water from downpipe ( 1 ) into water butt ( 5 ). 
     To make the diagrams clearer, the width of downpipe ( 1 ) has been exaggerated relative to that of water butt ( 5 ) and the vertical height compressed between bottom of downpipe ( 1 ) and the top of water butt ( 5 )—so as to show the detail within the bottom section of downpipe ( 1 ) more clearly. In other words, a real water butt ( 5 ) would typically be much wider and taller than it appears in these drawings—holding many more times the volume of water than does this lower section of downpipe ( 1 ). 
     Water butt ( 5 ) may be immediately beside or some distance from downpipe ( 1 ). It may be on the same level as the ground ( 2 ) beneath downpipe ( 1 ), or sitting up on a stand so as to allow a tap to be placed nearer the bottom of barrel ( 5 ) yet still be above the height of a bucket or watering can. The elevation of the bottom of barrel ( 5 ) relative to the lower end of downpipe ( 1 ) is of little importance. However, the upper fill level ( 6 ) above which barrel ( 5 ) would overflow through outlet hole ( 7 ) is important. This level generally should be above both the level of the bottom of downpipe ( 1 ) and the first flush level ( 8 ). 
     In this example, downpipe ( 1 ) is a simple vertical cylinder and is typically of circular, square or rectangular cross-section with walls made of plastic, iron, steel or concrete between 1 and 5 millimeters in thickness. However, downpipe ( 1 ) can be of any cross-section and could be at an angle. In this example the open outlet of the pipe, absent the invention, is a horizontal face a few centimeters above ground level ( 2 ). The explanation below assumes a circular cross-section and vertical pipe by way of example only. As long as the pipe is not horizontal, the invention can still work but requires a longer collection pipe to reach the required first flush ( 8 ) and overflow ( 6 ) levels. 
     Similarly, by way of example only, let us assume that the water butt ( 5 ) is full when the water in it is 1.5 meters deep and that it is on approximately the same level as the ground ( 2 ) beneath downpipe ( 1 ). Further, assume that there is typically 15 centimeters between the ground and the bottom of downpipe ( 1 ). Downpipe ( 1 ) itself is typically 68 mm in diameter and at least 3 meters high. 
     The invention consists of a cylindrical “boot” ( 11 ) which is clamped around the lower end of downpipe ( 1 ) so as to from a largely watertight seal. This allows water falling down the pipe to accumulate inside downpipe ( 1 ). This seal does not need to be tolerant of high pressure as the pressure will never exceed the depth of water butt ( 5 ) (1.5 m in this case), nor does it need to be perfect as any slight leakage will fall down through drain ( 3 ) in the same way that it did prior to the invention being attached. 
     Boot ( 11 ) can be clamped around downpipe ( 1 ) using a compressible watertight O-ring ( 12 ) and held in place by a jubilee clip ( 13 ) tightened by hand using butterfly nut ( 14 ). Other means of attachment are possible. For example, if downpipe ( 1 ) is designed to accept push-fit connection of a further section of downpipe ( 1 ), boot ( 11 ) may be made compatible with this connection style. As is the case with some existing rainwater diverters, it will be appreciated that a single design of boot, with appropriately stepped concentric profiles can be affixed to pipes of several different cross sections (large circular, small circular and square for example). 
     In the center of the lower face of boot ( 11 ) is a (typically) circular hole ( 15 ) of only slightly smaller diameter than downpipe ( 1 ) itself. This hole ( 15 ) is normally blocked by a circular disc ( 16 ) of slightly larger diameter than the hole ( 15 ). The outer lower edge of disc ( 16 ) and/or edge of hole ( 15 ) are covered in a washer of silicone or similar material so as to provide a watertight seal when disc ( 16 ) sits over hole ( 15 ) under its own weight or, more tightly, when water is pushing down on it from above. This type of seal is common in toilet cisterns, particularly in the United States (less so in the United Kingdom). From the center of disc ( 16 ) a narrow axial rod ( 17 ) projects upwards for approximately 50 mm. This rod is constrained to move within a vertical hollow cylindrical guide ( 18 ) of internal diameter slightly greater than that of rod ( 17 ). This allows disc ( 16 ) to move upwards by approximately 25 mm when lifted by a force applied upwards through rod ( 17 ). Guide cylinder ( 18 ) is held centrally within boot ( 11 ) by, typically, three or more narrow radial spokes ( 19 ) connecting it to the wall of boot ( 11 ). 
     In one side of boot ( 11 ) is a circular hole ( 22 ) with a central groove holding a circular flexible rubber, silicone or similar flange ( 23 ). Flange ( 23 ) is of slightly narrower diameter than transfer pipe ( 4 ), which can therefore be pushed through flange ( 23 ) giving a substantially though not necessarily perfectly waterproof seal around this pipe. Optionally, transfer pipe ( 4 ) may have a corrugated outer surface allowing the material of flange ( 23 ) to locate between successive corrugations providing a better seal than it would on a smooth pipe. 
     Inside boot ( 11 ), transfer pipe ( 4 ) may be bent through approximately ninety degrees and either expands into or is connected to a (typically) larger diameter collection pipe ( 24 ) that passes through a collar ( 25 ) in the centre of boot ( 11 ) (and hence downpipe ( 1 )). As with cylindrical guide ( 18 ) this collar ( 25 ) is held in the centre of boot ( 11 ) by typically three or more thin radial spokes ( 26 ) connecting it to the wall of boot ( 11 ). 
     Collection pipe ( 24 ) projects up the downpipe to several centimeters above the overflow level of water butt ( 6 ). As the pipe is flexible it will, in practice, meander slightly but is stiff enough that it does not double over when pushed up downpipe ( 1 ). The top of collection pipe ( 24 ) is sealed ( 27 ) to prevent water entering through this end of pipe ( 1 ). A rounded cap with a slight overhang is preferably used so as not to catch on any internal joints in the walls of downpipe ( 1 ) as it is pushed up pipe ( 1 ), but also to shield the openings below it from water falling downwards into them. Below this seal ( 27 ), but above a “first-flush level” ( 8 ), the walls of the collection pipe ( 24 ) are perforated so as to allow any water surrounding the pipe to enter it. Preferably, these perforations provide both a filtering mechanism (by being small but numerous) and a deflection mechanism. For example, as shown in  FIG. 2 , each perforation can be produced by making two cuts ( 28 ), ( 29 ) forming a notch with the point at the bottom. Pushing the tip of flap ( 30 ) thus produced outwards at the forms a “barb” that deflects any water and debris running down the outside of the tube. Water rising around collection tube ( 24 ) will easily flow into the tube through these holes but water running down the tube will not. 
     Alternatively, larger holes may be made in the walls of the tube and this section of tube wrapped in a porous material or fine mesh such as that used in the filters within vehicle fuel tanks or swimming pool clearing nets. Either approach achieves the goal of filtering out larger pieces of debris which will therefore accumulate within the base of downpipe ( 1 ) rather than enter collection tube ( 24 ). 
     Whether using overhung perforations or a mesh filter, the fact that this section of collection pipe ( 24 ) is typically 50 cm or more in length means that a large surface area can be provided—allowing easy passage of significant volumes of water, even if some particulates become lodged in the filter or perforations. 
     As collection pipe ( 24 ) is watertight below first flush level ( 8 ), when rain begins to fall, the initial flush of water (containing the bulk of the dust and debris collected on the roof and gutters since the previous rain) collects in boot ( 11 ) and bottom of downpipe ( 1 ). On its way there, very little water enters collection tube ( 24 ) due to the fact that the water tends to flow down the outside of downpipe ( 1 ) and overhanging flaps ( 30 ) and overhanging seal ( 27 ) deflect it from the perforations beneath them. Only after the water level inside downpipe ( 1 ) rises above first flush level ( 8 ) does it start to enter collection pipe ( 24 ). 
     Collection pipe ( 24 ) is connected via narrower-gauge transfer pipe ( 4 ) to the inside of water butt ( 5 )—typically via a screw connector or jubilee clip to a male to male nipple that is screwed into in a hole ( 9 ) near the bottom of water butt ( 5 ) using rubber washers to provide a watertight seal. On the inside of the nipple, optionally a duck-billed valve ( 10 ) is screwed or clamped. 
     If the water level in butt ( 5 ) is lower than first flush level ( 8 ), water will begin to flow down collection pipe ( 24 ), through transfer pipe ( 4 ) and hole ( 9 ) in the side of butt ( 5 ) and (if present) through low differential pressure valve ( 10 ). 
     If the level of water in the butt is higher than first-flush level ( 8 ), water will continue to accumulate in downpipe ( 1 ) and collection pipe ( 24 ) but will not flow from it into butt ( 5 ) until the height of water in downpipe ( 1 ) (and hence collection pipe ( 24 ) exceeds that in butt ( 5 ). 
     Thus as water continues to flow down downpipe ( 1 ) it will flow through collection pipe ( 24 ) and transfer pipe ( 4 ) into butt ( 5 ), with the water level inside downpipe ( 1 ) exceeding that in butt ( 5 ) by the small amount needed to open valve ( 10 ). 
     When water butt ( 5 ) is full to overflow level ( 6 ), the invention ensures that any further water coming down downpipe ( 1 ) is released down drain ( 3 ), thus avoiding any problems with overflow at water butt ( 5 ) itself and the consequent need to pipe water away from the top ( 7 ) of butt ( 5 ) to the nearest drain—typically the one ( 3 ) away from which the water has just been diverted in the first place. 
     The overflow mechanism in  FIG. 1  is achieved by means of a hollow cylindrical float ( 21 ) inside the upper, perforated end of the collection pipe ( 24 ). This is of slightly smaller diameter than the inside of collection pipe ( 24 ) and is blocked from falling down the tube by a constriction or obstruction such as a pair of pins ( 31 ) or wires pushed through the walls of the pipe at right angles to each other. As the water level inside downpipe ( 1 ) reaches the maximum required, this float will start to rise until it is blocked—just a few centimeters higher by sealed end ( 27 ) of the pipe. The small gap between obstruction ( 31 ) and top seal ( 27 ) is typically only 25 mm or so greater than the height of float ( 21 ) so the float can only move up and down by this amount. 
     A strong, lightweight smooth cord ( 20 )—such as fishing line—is affixed to a lower end of float ( 21 ). This has been threaded through the wall of collection pipe ( 24 ) via a small hole not much wider than the cord ( 20 ) itself, ideally in the bend of the pipe directly above the center column ( 17 ) of lift-check valve ( 16 ). Cord ( 20 ) is threaded through a tiny axial hole in the center of rod ( 17 ) and appears out the bottom of disc ( 16 ). There, a clip ( 32 ) grips cord ( 20 ) tightly—so that when float ( 21 ) pulls upwards on cord ( 20 ), clip ( 32 ) stops it from being pulled back through the hole in disc ( 16 ) and instead forces disk ( 16 ) to rise, opening hole ( 15 ) and allowing water to flow out and down drain ( 3 ) as it would have done in the absence of the invention. 
     As water leave downpipe ( 1 ), float ( 21 ) drops down again, letting valve ( 16 ) reseat, shutting off the flow of water. As water continues to enter the top of downpipe ( 1 ), float ( 21 ) and attached valve ( 16 ) keep the water level close to this maximum level. 
     As collection pipe ( 24 ) is typically less than half the diameter of downpipe ( 1 ), and valve ( 16 ) at the bottom lifts 25 mm above hole ( 15 ), water can flow through downpipe ( 1 ) at almost the same rate it could prior to the invention being installed. As the peak flow rate is typically determined by that of the (gently inclined) gutters feeding downpipe ( 1 ) rather than downpipe ( 1 ) itself, the overflow path can thus be designed to cope with storm flow rates as well as the gutters do. 
     Note that this overflow mechanism will typically only be operated a few times a year—during the heaviest rain storms (when the rate of inflow of water through the top of downpipe ( 1 ) exceeds the rate at which it can flow out to water butt ( 5 ) via pipe ( 4 ) and also when water butt ( 5 ) is already full. In either case, the overflow starts only once the head of water inside downpipe ( 1 ) reaches preset overflow level ( 6 ). There is therefore typically 1.5 m head of water pushing the bottom of the column of water out through valve ( 16 ). This rush of water helps to automatically clean out any debris that has gathered in the bottom of downpipe ( 1 ) since the previous overflow incident. 
     However, there is still a chance that debris accumulates above valve ( 16 ) and eventually stops it from being lifted and/or opening effectively. Although it is possible to push valve ( 16 ) up by inserting ones fingers into hole ( 15 ) and teasing out leaves, dirt etc. this may be insufficient to clear larger debris. The apparatus may be temporarily removed by loosening the butterfly nut ( 14 ), dropping boot ( 11 ) and attached components so that debris can be removed via the now exposed top of the boot. 
     Alternatively, an access door, typically 50 mm high and extending for 120 degrees or so around the upper edge of boot ( 11 ) can be provided. This is typically hinged at one end and snap-fit at the other end or snap-fit at both ends. A rubber grommet inset around the edge of this trap door provides a sufficiently watertight seal when the door is closed. Projecting tabs over the snap-fit end(s) allow a user to pop the door open, insert a hand or tool to remove any debris and then snap the door shut again. 
     Although  FIG. 1  shows collection pipe ( 24 ) perfectly straight, vertical, and central, it is actually preferable that both pipe ( 24 ) and float ( 21 ) within it are very flexible and can accommodate quite a small bend radius. This is achieved by using a thin walled pipe—typically of an elastic polymer. This allows collection pipe ( 24 ) and the float ( 21 ) within it to be inserted into downpipe ( 1 ) even when the bottom edge of downpipe ( 1 ) is only a few inches above the ground ( 2 )—or where there is a ninety degree bend at the bottom of the pipe. In this case, collection pipe ( 24 ) and float ( 21 ) will meander slightly as they are pushed up downpipe ( 1 ). The walls of downpipe ( 1 ) will support flexible inner collection pipe ( 24 ), which will remain substantially vertical as it snakes its way upwards. 
     Constraining float ( 21 ) within the limited space at the top of collection pipe ( 24 ) ensures that cord ( 20 ) cannot become tangled and that there is little to no scope for float ( 21 ) to become trapped—even where collection pipe ( 24 ) is not perfectly straight and vertical. 
     Similarly, to allow the invention to be used inside non-vertical pipes, it is important that float ( 21 ) is able to rise and fall inside the section at the end of collection pipe ( 24 ) when this is at, say, 45 degrees to the vertical. To avoid float ( 21 ) sticking inside collection tube ( 24 ), the latter should be smooth on the inside and the materials of float ( 21 ) and collection tube ( 24 ) should be selected for minimum friction. 
     Note that in the case of a non vertical downpipe ( 1 ) the “barbs” shown in  FIG. 3  also serve to hold the surface of collection tube ( 24 ) slightly off the lower wall of downpipe ( 1 ) on which it would otherwise rest. This again helps to stop water running down downpipe ( 1 ) from entering collection tube ( 24 ) until the column of water held inside the downpipe rises to the level at which the perforations start ( 8 ). 
     The upward force provided by the buoyancy of float ( 21 ) when fully submerged must exceed the weight of valve ( 16 ), column ( 17 ), cord ( 20 ) and clip ( 32 ) by at least as much force as is pushing down on the valve due to the column of water above it. Thus the weight of these components, the area of valve ( 16 ) and overflow height ( 6 ) determine the minimum volume of float ( 21 ) and hence an appropriate diameter of collection pipe ( 24 ). 
     Note that clip ( 32 ) allows the effective length of cord ( 20 ) to be adjusted from outside without having to dismantle the device. When downpipe ( 1 ) is empty of water, having positioned the appropriate length of collection pipe ( 24 ) above collar ( 25 ), clip ( 32 ) can be slid up or down cord ( 20 ) so that cord ( 20 ) is just taut when valve ( 16 ) is firmly seated. Any vertical movement of float ( 21 ) will then immediately lift valve ( 16 ). Similarly, the height of collection pipe ( 24 ) can be adjusted by pulling or pushing inlet pipe ( 4 ) through flexible flange ( 23 ). This allows the point at which valve ( 16 ) opens to be adjusted so that it does so when the water level in butt ( 5 ) is at required maximum level ( 6 ). 
     The tiny hole in valve ( 16 ) through which cord ( 20 ) passes also serves to let the water within downpipe ( 1 ) drip away slowly over the space of several hours. This effectively resets the “first flush” mechanism as the bottom of downpipe ( 1 ) will then have to refill to the first flush level ( 8 ) before water again flows into collection pipe ( 24 ) and hence via transfer pipe ( 4 ) to water butt ( 5 ). Where this hole is left open in this manner, it is essential to either install some form of backflow prevention such as valve ( 10 ) or to connect transfer pipe ( 4 ) to an inlet just below overflow level ( 6 ) to avoid the contents of water butt ( 5 ) slowly leaking away though this hole. 
     Often, such downpipes ( 1 ) have a ninety-degree bend at the bottom to direct water away from the wall to which they are affixed. In other cases the pipe is directly above a drain opening ( 3 ) and water drops straight down through the end. In cases where the bend at the bottom is not easily removed or it is important that any water leaving this end does so at exactly the same point as it did with the bend present, a variant of the design can be used. 
     Where a downpipe has a vertical open face rather than the horizontal open face shown in  FIG. 1 , it will be appreciated that vertically rising check valve ( 16 ) and associated guide rod ( 17 ) and cylinder ( 18 ) could be replaced by a flapper valve slightly angled from the vertical and hinged at the top so as to fall shut under its own weight. In this case cord ( 20 ) would be attached to the lower edge of the valve, pulling it open as float ( 21 ) rises. 
       FIG. 3  shows a simpler approach that achieves the same goals but without any moving parts. This is therefore more reliable than the previous version but has slightly lower peak flow rate under overflow conditions. 
     In this approach, two hollow pipes—overflow pipe ( 33 ), and collection pipe ( 34 )—are pushed up inside downpipe ( 1 ) and held in place by a bung ( 35 ). Although not shown in  FIG. 3 , the two pipes may be strapped or tied loosely together at intervals so as to keep them substantially parallel and to avoid either doubling back on itself as they are pushed up downpipe ( 1 ). 
     Bung ( 35 ) is a deformable, slightly tapered bung (narrower at the top edge) typically made of a soft waterproof, deformable material (e.g. neoprene, rubber or silicone). A plan view of an example bung is shown in  FIG. 4 . The thicker, central section ( 36 ) thins towards the top allowing it to be easily inserted into the downpipe and pushed up to form a tight fit. Holes ( 37 ) and ( 38 ) are of slightly smaller diameter than pipes ( 33 ), ( 34 ) respectively that fit into them so as to form a watertight seal around the pipes. Optionally, a rigid collar may be provided around these holes and/or a rigid insert provided within the pipes to as to strengthen them at the point they pass through the bung—allowing a tight seal to be achieved without crushing the pipes. Pinhole ( 41 ) allows water to dribble away very slowly, emptying the chamber formed at the bottom of downpipe ( 1 ) between rain showers. 
     Downpipe ( 1 ) is pushed down into a groove ( 39 ) to form a seal when the bung is in place. In this example, eight flaps ( 40 ) of thinner material, each of width approximately equal to one eighth of the circumference of the downpipe ( 1 ) can be folded up once the bung is in place so as to completely surround the bottom end of the downpipe ( 1 ). A jubilee clip ( 42 ) or similar is tightened around the outside of the eight flaps ( 40 ) that now surround the bottom of the downpipe ( 1 ). This is preferably tightened by a butterfly nut ( 43 )—allowing the bung to be fitted and subsequently removed easily, without the need for tools, for cleaning, adjusting or to be moved to another downpipe. The length of the two pipes ( 33 ), ( 34 ) can be altered independently by pulling them through holes ( 37 ), ( 38 ) and any debris that has accumulated above the bung can be removed—with much of it simply dropping down as the bung is released. 
     Alternatively, the bung may be held in place using a metal cage that is then tightened around the end of the downpipe ( 1 ) a few inches above the opening. This is much the same principle as is used to hold a champagne cork in a bottle using a wire cage. 
     Note that refinements to the design of the bung allow for optimisation of the cost of materials and for a single bung design to be adapted to a variety of downpipe cross sections. The former is achieved by making the bung largely of a cheaper, rigid plastic with thinner rings of deformable rubber around these rigid elements. The latter can be achieved by manufacturing a single bung as a series of concentric shapes, each almost but not quite cut away from the one inside it. The outer shape fits the largest downpipe profile supported. To use it in smaller downpipes, the installer tears off the outer ring or segments reducing the size to that of the next smallest downpipe profile. Where a circular and square profile overlap, four segments can be removed to drop from circular to square profile. In all cases, the bung ( 35 ) provides a snug fit inside the downpipe ( 1 )—in much the way that a tapered cork can be pushed into the neck of a bottle. 
     To facilitate the insertion of the pipes ( 33 ), ( 34 ), the bung ( 35 ) may be made in two halves or hinged at one edge. This allows the bung ( 35 ) to be clamped around the two pipes with the pipes projecting through the bung ( 35 ) and hence up the downpipe ( 1 ) to whatever height is desired. The remainder of the pipes protrudes from the bottom of the bung ( 35 ) once fitted. 
     Collection pipe ( 34 ) is sealed at the top with a slightly overhanging cap ( 44 )—so as to prevent water falling down the downpipe ( 1 ) from entering it directly. The top section, above the first flush level ( 8 ) is typically 10 to 30 cm in length and is perforated as described previously with relation to  FIG. 2  or has larger gaps in the walls which are then covered with a fine mesh filter. Either approach allows water to enter easily from the sides but blocks all but the finest debris from entering. The lower section of pipe, below the first flush level ( 8 ) is solid and watertight hence the height of the bottom edge of the perforated section above the top of the bung multiplied by the cross-sectional area of the downpipe ( 1 ) minus those of the pipes ( 33 ), ( 34 ) determines the volume of water that must accumulate in the bottom of the downpipe ( 1 ) before any flows to the water butt ( 5 ) which is connected to transfer pipe ( 4 ), again via one-way valve ( 10 ), so as to allow water to flow into the butt ( 5 ) but not out of it. 
     Overflow pipe ( 33 ) is typically of larger diameter than the collection pipe ( 34 ). There is a trade-off between peak overflow rate and first flush volume. A larger overflow pipe ( 33 ) improves the former but reduces the latter. This pipe ( 33 ) is also sealed with an overhanging cap ( 45 ) at the top and has a perforated section immediately below this cap. Again, water falling downwards does not enter significantly. In this case the perforations are typically vertical slits 75 mm tall and at least 10 mm wide. This makes the top section ( 46 ) of this pipe more of an open cage structure—deliberately allowing debris in the water to flow through the holes without blocking them. This allows any floating debris—such as fresh leaves—to flush out of the system whenever it overflows. The height of the bottom of this section of pipe above ground level determines the maximum height of the water column that can accumulate inside the downpipe ( 1 ) before any excess overflows straight down the overflow pipe ( 33 ) and into the drain ( 3 ) beneath the downpipe ( 1 ). This height should therefore be set to match the maximum fill level ( 6 ) of the water butt ( 5 ). This ensures that the water column in the downpipe ( 1 ) can never push water through pipe ( 4 ) if the butt is already full. 
     Note that in this design, it is immaterial whether the end of the downpipe ( 1 ) is vertical, horizontal or any angle in between. The bung ( 35 ) simply fits in the end of the downpipe ( 1 ) and, if the overflow pipe ( 33 ) is cut off as it exits the bung, any water exiting it does so in the same direction it would have done in the absence of the apparatus. Alternatively, the open end ( 47 ) of the overflow pipe ( 33 ) can be directed down into the drain ( 3 ) allowing subsequent adjustments to be made to the overflow level ( 6 ): increasing it by pushing the overflow pipe higher or reducing it by pulling the pipe downwards then retightening the bung around the downpipe ( 1 ). 
     A variant on this design is shown in  FIG. 5 . Rather than pushing two separate pipes ( 33 ), ( 34 ) of different lengths up the downpipe ( 1 ), a single, larger diameter pipe is used ( 48 ). This is divided internally into two chambers that provide the same functions as the two separate pipes of  FIG. 3 . With fewer parts and a more streamlined shape, it is easier to insert this assembly into the downpipe ( 1 ) and to position the bung ( 35 ) around it. The overflow grille ( 50 ) can be larger while the filter-covered or perforated area at the top of the collection chamber within the tube extends around at least part of the outside of the combined tube. 
     Although the invention has, thus far, been described as an add-on to an existing downpipe ( 1 ) it will be appreciated that the entire mechanism can be built into a downpipe section, thus avoiding the need for the “boot” ( 11 ) or bung ( 35 ) to be clamped on to the bottom of the otherwise open pipe. An example of this is shown in vertical cross section in  FIG. 6 , and horizontal section through the lower section (just below the first flush level ( 8 )) in  FIG. 7 . In this approach, the lower end of the downpipe is moulded or extruded to provide the overflow channel ( 48 ) and opening ( 51 ) and pinhole for first flush reset ( 52 ) in the otherwise sealed accumulation chamber ( 53 ). Collection of water for the water butt ( 5 ) is via small holes or filter mesh ( 49 ) between the first flush level ( 8 ) and overflow level ( 6 ) as before but now in a built-in channel down one side of the downpipe ( 1 ). Alternatively, rather than dividing the pipe as shown in  FIG. 7 , a concentric design with central collection column and annular overflow pipe or other geometric designs can be used. 
     As in the earlier figures, it will be appreciated that the transfer pipe ( 4 ) to the water butt ( 5 ) may be a continuation of the collection pipe or chamber inside the downpipe ( 1 ) or there may be a connector provided at the bottom of the downpipe allowing the pipes to be of different diameter and/or construction. Transfer pipe ( 4 ) is typically garden hose while that inside the downpipe is preferably a more flexible, thin-walled pipe which is easily bent as needed when inserting it. 
     In the case of a built-in unit as in  FIG. 6 , the option of removing the bung ( 35 ) to clean the collection area is not available. A hinged section at the bottom of the pipe with a push fit catch—similar to that described earlier with respect to the boot ( 11 ) of  FIG. 1-would  allow simple snap-open adjustment and cleaning. 
     For a downpipe section as shown in  FIG. 6 , the peak flow rate under storm conditions is not as great as it would have been for an unencumbered flow through the downpipe. In further variants, therefore, the cross-section of the pipe can be increased to provide larger first-flush collection volumes and/or to provide an overflow exit ( 51 ) of the same size as the original downpipe—with the collection pipe and accumulation areas being accommodated within this extra cross-sectional area. This results in a slightly wider section at the bottom of a downpipe. 
     Unlike the add-on solutions of the earlier Figures, the overflow height ( 6 ) of the apparatus shown in  FIG. 6  cannot be adjusted simply by raising or lowering an overflow pipe. Instead, the walls of the internal dividers could contain punch-outs allowing the overflow level to be set before the bottom section of downpipe is connected. Alternatively, a strip of plastic pushed up through a guide could progressively cover the holes in the overflow section ( 50 ) and hence by pulling this out from the bottom of the pipe, the height of the lowest exposed overflow hole could be adjusted. 
     In all the previous examples, note that the use of a non-return valve ( 10 ) is only required if the bottom of the downpipe is not watertight and where the transfer pipe ( 4 ) attaches to the water butt below the fill level ( 6 ). There is thus a trade-off between having an automatic trickle release reset on the first flush collector and the need for a non-return valve. If the trickle release (provided by the pinhole in the center of the valve ( 16 ) of  FIG. 1 ; the pinhole ( 41 ) in the bung of  FIGS. 3 ,  4  and  5  or the pinhole ( 52 ) in the bottom of the collection chamber of  FIG. 6 ) is blocked, then the water level in the bottom of the downpipe ( 1 ) and the water butt ( 5 ) will equalise and there is no need for valve ( 10 ). A refinement to the design is therefore to mould the bung ( 35 ) or downpipe section so that the holes ( 41 ) and ( 52 ) are not opened unless they are deliberately punched out or the end of projecting nipple is cut off. 
     As the invention relies on maintaining a column of water slightly higher than the water level in the water butt(s) that it feeds, it is important that the downpipe ( 1 ) is reasonably watertight. Where a non-return valve ( 10 ) is used, slight dripping is unimportant as long as the volume escaping is very much less than that flowing to the water butts. However, in some cases, it may be appropriate to seal a leaking joint within the lower section of the downpipe ( 1 ). A compressible rubber or plastic ring may be placed around the joint and compressed around it with a jubilee clip to form a substantially watertight seal. It will be appreciated that there are many alternative approaches to sealing, caulking or otherwise blocking such leaks. 
     An alternative to the deformable bung of  FIG. 4  is to use an inflatable collar. This avoids the need for flaps ( 40 ) and external fixation devices such as the jubilee clip ( 42 ) and butterfly nut ( 43 ). Such an approach is much less visible as the whole of the inflatable collar can be pushed up inside the downpipe ( 1 ) and inflated, gripping the pipe(s) going through it and the inside of the downpipe wall. All that is then visible outside the downpipe is the transfer pipe ( 4 ) taking the water to the water butt ( 5 ). This approach is ideal for historic buildings where attachments to the downpipes would detract from the appearance of the property. 
     The inflatable collar, being (when deflated) much smaller than the cross-section of the pipe, can be designed to grip the collection pipe ( 34 ) much further up—at the bottom of the perforated section if required. It can then be inserted up to the appropriate height and inflated well inside the downpipe ( 1 ). Although this reduces the first flush volume, it significantly reduces the length of overflow pipe ( 33 ) required since this does not need to project below the collar, merely to pass through it. As the overflow pipe is the bulkiest item in the design, this provides a more compact and material efficient design. 
     The very nature of such inflatable collars means that a single collar design can accommodate a range of downpipe sizes and shapes. Metric and imperial sized domestic downpipes differ in size by a few millimeters. Square, circular and rectangular downpipes all exist. A suitable flexible collar will fill the inside of any of these shapes as it is inflated. 
     Further refinements to the design include measures to make it easier to insert the collection and/or overflow pipes. Rounded edges and low friction material on the tops of the pipes help to stop them catching on internal obstructions or joints as they are pushed up the pipe. 
     A concern on very tall downpipes is that, should the downpipe ( 1 ) completely fill with water in a storm, the force acting down on the boot ( 11 ), bung ( 35 ), or inflatable collar at the bottom of the pipe may push it out. This can be countered by extending the overflow pipe ( 33 ) upwards with a watertight (and hence airtight) section between the top of the grille ( 46 ) and overhanging cap ( 45 ). Even if the water column inside the downpipe rises above the top of the grille ( 46 ) an air chamber is maintained in this top section of the overflow pipe. This provides up-thrust due to Archimedes principle and pulls the pipe ( 33 ) upwards—reducing the net downward force on the bung ( 35 ). The ratio of the cross-sectional area of the overflow pipe to that of the downpipe as a whole determines the net effect of additional water in the pipe. 
     An alternative approach to connecting the apparatus to the water butt ( 5 ) can be taken—in which the transfer pipe ( 4 ) is connected to an inlet at the overflow level ( 6 ) of the water butt. This may be done via the overflow outlet ( 7 ). In this case, water would not flow up the transfer pipe ( 4 ) and into the butt ( 5 ) until the column of water inside the downpipe ( 1 ) reaches the height ( 6 ) of the said inlet ( 7 ). The advantage is that, without any requirement for a valve ( 10 ), the water butt ( 5 ) cannot empty through the transfer pipe ( 4 ) even if the apparatus is removed for cleaning or the chamber at the bottom of the downpipe ( 1 ) is otherwise not watertight. Note that the porous/perforated section of the collection pipe does not need to be at this height. It can remain lower but the water will still not flow until the head of water above it reaches the new level ( 6 ) at which the transfer pipe enters the water butt ( 5 ). 
     In this configuration, the initial “first flush” volume of water that must flow down the downpipe ( 1 ) before the barrel starts to fill is significantly greater than when transfer pipe ( 4 ) connects to the base ( 9 ) of the water butt ( 5 ). This can be offset by the apparatuses of  FIGS. 3 ,  4  and  6  deliberately having a very wide overflow pipe ( 33 ), or section of pipe ( 48 ). This restricts the cross-sectional area of the chamber, which must fill before flow to the water butt starts. Under extreme flow conditions (typically summer storms) this approach provides a lower flow rate to the butt ( 5 ) as the head of water above the inlet level must be restricted more than in the case where the transfer pipe ( 4 ) enters low ( 9 ). With the transfer pipe ( 4 ) connected to overflow outlet ( 7 ) the butt ( 5 ) will overflow either through a further, slightly higher hole or over the lip of the butt. In either case there is typically only a few centimeters between these levels. There is nothing to stop the traditional approach of an overflow pipe being taken from this higher level in the water butt ( 5 ) to an appropriate drain or soak-away but if it is important to cope with excess water in the downpipe, the overflow mechanism within the apparatus must be adjusted to operate between these levels. There is therefore a maximum of a few inches of head pushing water into the water butt ( 5 ). Note, however, that this is no worse than the case with prior art apparatus inserted into the downpipe at this level. These typically have a collection chamber only a few centimeters deep and hence have similarly restricted peak flow rates. 
     The skilled person will be aware of a range of possible modifications of the various embodiments described above. Accordingly, the present invention is defined by the claims and their equivalents.