WO2007028207A1

WO2007028207A1 - A flow control fitting

Info

Publication number: WO2007028207A1
Application number: PCT/AU2006/001310
Authority: WO
Inventors: Matt Goodall Parsons
Original assignee: Samaran International Pty Ltd
Priority date: 2005-09-07
Filing date: 2006-09-07
Publication date: 2007-03-15
Also published as: NZ564057A

Abstract

A fitting for controlling the rate of flow of liquid in a conduit, including: a body having one or more openings formed through said body, such that, when said liquid defines a level in said conduit, at least one of said openings is at least partially submerged in said liquid so as to define an effective flow aperture relative to said level for controlling the rate of flow of said liquid through said body; wherein the selective rotation of said body enables adjustment of the size of said effective flow aperture.

Description

A FLOW CONTROL FITTING

FIELD

The present invention relates to a fitting for controlling the rate of flow of a liquid in a conduit.

BACKGROUND

There is a need to split the flow of liquids issuing from a holding tank (e.g. injunction pits) into desired proportions. This is a requirement for the proper management of on-site sewage processing systems. For example, as shown in Figure 1, an on-site sewage processing system 100 collects sewage effluent from sewer pipe 102 in a septic tank 104. After primary treatment in the septic tank 104, on-site sewage effluent is typically directed to absorption trenches 106, 108 and 110 located below the ground. An absorption line 112, 114 and 116 (e.g. a perforated pipe) is located within each of the aggregate filled absorption trenches 106, 108 and 110. Space, terrain and trench length constraints usually requires there to be a number of absorption lines 112, 114 and 116 that are spread out in a down slope direction. This arrangement typically allows the sewage effluent to flow to the absorption trenches 106, 108 and 110 under the force of gravity.

On-site sewage is best managed if it is spread out evenly over the absorption trenches 106, 108 and 110, in accordance with the tested soil percolation and designed long-term absorption characteristics of the soil. However, due to historical circumstances, some the absorption trenches 106, 108 and 110 are currently flooded beyond their designed application rates in a serial fashion. The junction pits 118, 120 and 112 that are typically used in this arrangement is shown in Figure 2 (as described in Victoria Environmental Protection Agency (EPA), 1996, Code of Practice - Septic Tanks). The common problem with the arrangement shown in Figure 2 is that under normal operation, a small number of absorption trenches (e.g. 106 and 108) are flooded beyond their assessed long-term absorption capacity and consequently fail in a premature serial fashion. However, it is often difficult to control and/or adjust the flow of effluent into different absorption trenches. For example, given the small spatial confines of the junction pits typically used in the on-site sewage processing industry, it is very difficult for plumbers and drainers to accurately assess the flow level in the pit, and to construct apertures for controlling the flow proportions and outlet levels to and from the junction pit.

An object of the present invention is to address one or more of the above problems, or to at least provide a useful alternative to existing flow control fittings or devices.

SUMMARY

According to the present invention there is provided a fitting for controlling the rate of flow of liquid in a conduit, said fitting including: a body having one or more openings formed through said body, such that, when said liquid defines a level in said conduit, at least one of said openings is at least partially submerged in said liquid so as to define an effective flow aperture relative to said level for controlling the rate of flow of said liquid through said body; wherein the selective rotation of said body enables adjustment of the size of said effective flow aperture.

Preferably, said body includes means for coupling said body to an open end of said conduit. Once the body has been rotated to define an effective flow aperture of a selected size, the body may be securely sealed to the conduit so as to reduce movement of the body with respect to the conduit.

Preferably, said body includes means for adjusting the height of said body relative to said level. The means for height adjustment includes an elbow joint for coupling with said fitting, said elbow joint also for coupling to said conduit. Preferably, said openings define one or more flow control regions, each said region for defining a corresponding said effective flow aperture of different size relative to said level.

Preferably, at least one of said regions defines a said effective flow aperture for allowing a high rate of flow relative to the rates of flow for other said regions.

Preferably, at least one of said regions defines a said effective flow aperture for allowing a rate of flow of around 50% of said high rate of flow.

Preferably, at least one of said regions defines a said effective flow aperture for allowing a rate of flow of around 33% of said high rate of flow.

Preferably, at least one of said regions defines a said effective flow aperture for allowing a rate of flow of around 25% of said high rate of flow.

Preferably, said effective flow apertures for said regions are defined by a single said opening.

Preferably, said openings define one or more weirs, each said weir corresponding to a different one of said regions.

Preferably, each of said weirs is substantially V-shaped.

Preferably, each of said weirs includes a rounded weir invert portion.

Preferably, each of said weirs includes a knife edge.

Preferably, said fitting is made of a plastic material, such as PVC, polythene or polypropylene plastics.

Preferably, said body is rotatable along a cross-sectional axis of said body. The present invention also provides a conduit including a fitting as described above.

The present invention also provides a fitting for coupling to an end portion of a conduit for controlling the rate of flow of liquid in a conduit, said fitting including: a disc-like body having an opening formed therethrough, said opening being shaped to form one or more respective weirs, such that, when said liquid defines a level in said conduit, at least one of said weirs is at least partially submerged in said liquid so as to define an effective flow aperture relative to said level for controlling the rate of flow of said liquid through said body; . wherein said body is selectively rotatable relative to said conduit to one or more predefined positions, each said position for defining a different said effective flow aperture, wherein said body, in use, is coupled to said conduit in one of said predefined positions.

The present invention also provides a method for controlling the rate of flow of liquid in a conduit using a fitting as claimed in any one of claims 1 to 16, the method including the steps of: i) rotating said fitting relative to said conduit to an orientation that allows one of the one or more openings of said fitting to form an effective flow aperture relative to the level of the liquid in said conduit; and ii) coupling said fitting to said conduit at said orientation.

The present invention also provides a method for controlling the flow of liquid through a plurality of conduits using fittings as claimed in any of claims 1 to 16, said method including the steps of: i) rotating each said fitting relative to said conduits to orientations that allow said fittings to form effective flow apertures relative to the level of the liquid in each said conduit; and ii) coupling each of said fitting to said conduits at orientations; whereby the relative flows of liquid through respective conduits is in accordance with a predetermined distribution. The steps of the above methods can be performed in any order, and is not limited to the order as described above.

The present invention also provides a sewage dispersal system for controlling the flow of sewage through a plurality of conduits using fittings as claimed in any one of claims 1 to

16, wherein said fittings are coupled to said conduits at predetermined respective orientations, said orientations being defined by rotating each said fitting relative to said conduits to allow said fitting to form effective flow apertures relative to the level of the liquid in each said conduit, so that the relative flows of liquid through respective conduits is in accordance with a predetermined distribution. - ' ^' > .

The present invention provides a number of advantages, firstly by the construction of a fitting for a conduit (or pipe) that has predetermined proportional apertures (or weirs) for adjusting the rate of flow of liquid in the conduit (e.g. in the junction pit and absorption line arrangements) by selective adjustment of the fitting. A further advantage is the ability to adjust the height of the fitting relative to the surface level of the liquid, by rotating the fitting, so as to enable equal weir outlet levels for more accurate split flow conditions. This is particularly advantageous where the common weir outlet level in the conduit is different to the ideal common weir outlet level for each respective fitting (due to pipe level inaccuracy during construction).

The present invention is useful in providing a simple way to enable the proportional distribution of the flow of liquid in multiple conduits (e.g. extending from a holding tank or junction pit). The present invention is further advantageous by providing an easier and more economical way to control flow rate and/or flow distribution, in light of the difficult human and environmental constraints presently associated with such a task.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a diagram of the components of an on-site sewage dispersal system; Figure 2 is a cross-sectional view of a junction pit in existing on-site sewage dispersal systems;

Figure 3 is a front view of a flow control fitting; Figure 4 is a cross-sectional view of the flow control fitting;

Figure 5 is a cross-sectional view of a junction pit in the on-site sewage dispersal system after installation of flow control fittings to the inlet and outlet pipes; Figure 6 is a top view of the junction pit shown in Figure 5;

Figure 7 is a diagram of the rotational adjustment of the fitting to compensate for pipe level inaccuracy; ' ^{■; ;}

Figure 8 is a cross-sectional view of a junction pit in the on-site sewage dispersal system after installation of flow control fittings and a height adjustment elbow joint to compensate for substantial pipe level inaccuracy;

Figure 9 is a top view of the junction pit shown in Figure 8; Figure 10 is a diagram of an asymmetrical dispersal system; and

Figure 11 is a diagram of a symmetrical dispersal system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes a preferred embodiment of the present invention in the context of a specific area of application relating to on-site sewage dispersal systems. However, it is expected that the present invention may be useful in other applications, such as for the regulation or adjustment of the flow of liquid in a conduit in general (e.g. in aquaculture systems).

An on-site sewage dispersal system 100, as shown in Figure 1, includes a septic tank 104 which passes sewage effluent to a number of junction pits 118, 120 and 122 via a series of pipe 124, 126 and 128. Each junction pit 118, 120 and 122 may distribute the effluent into one or more underground absorption trenches 106, 108 and 110 via one or more perforated pipes 112, 114 and 116 located within the trenches. Alternatively, each junction pit (e.g. 118) may distribute the effluent to one or more other junction pits (e.g. 120). Figure 2 is a cross-sectional view of a junction pit 118, which is partially buried in the ground 202 and is covered by a lid 204. In a typical configuration, the junction pit 118 receives effluent from the septic tank 104 via an incoming pipe 124 (in a flow direction indicated by arrow B), and then distributes the effluent into an absorption trench 106 via the perforated pipe 112, or to another junction pit 120 via the outlet pipe 126 (in a flow direction indicated by arrow C). The outlet pipe 126 includes a 90° elbow outlet weir 206. The opening 208 of the outlet weir 206 is generally aligned with the top of the aggregate lfill 210 inside the absorption trench 106 (accessible via perforated pipe 112). Typically, the base level 212 of the absorption trench 106 is situated about 250mm below the top of the aggregate fill of the effluent 210 in the absorption trench 106. ^:

Figure 3 is a front view of a fitting 300 for controlling the flow of liquid in a conduit. A liquid, as referred to herein, is defined as any composition of matter that, as a whole, is capable of flowing and is able to conform to the shape of a container or a conduit for carrying the liquid. A liquid includes mixtures that include solid or semi-solid matter, such as that typically found in sewage effluent.

As shown in Figure 3, the fitting 300 includes a body 302 that has one or more openings formed through the body 302. The body 302 may have only one opening 304, and preferably, the edge of the opening 304 is shaped to form multiple weirs. The one or more openings (e.g. 304) define one or more flow control regions of the body 302. For example, in the configuration shown in Figure 3, the body 302 has only one opening 304, and different peripheral portions 306, 308, 310 and 312 of the opening 304 each respectively defines a different flow control region.

When the fitting 300 is coupled to a conduit (e.g. a pipe), the openings (or a portion of an opening 304) belonging to a particular flow control region defines an effective flow aperture relative to the surface level of the liquid in the conduit to control the flow of the liquid through the fitting 300 at a predetermined rate. This may be achieved in a number of ways. For example, the openings (or a portion of an opening 304) belonging to a flow control region becomes partially submerged in the liquid in the conduit so as to define an effective flow aperture relative to the surface level of the liquid. In this example, the openings (or a portion of an opening 304) act as a weir, which enables the rate at which the liquid flows through the opening(s) to be controlled based on the width, height and/or shape of the opening(s). The flow rate for V-shaped weirs 308, 310, 312, as shown in Figure 3, may be controlled by adjusting the apex angle 324 and/or the apex radius 326 of the weir. Alternatively, the one or more openings belonging to a flow control region may be sized so as to enable the liquid to flow through the opening(s) at a predetermined rate of flow when the opening(s) are fully submerged in the liquid in the conduit.

Different flow control regions of the fitting 300 enable the liquid to flow through the fitting 300 at different rates of flow. In the configuration shown in Figure 3, different peripheral portions 306, 308, 310 and 312 of an opening 304 may be arranged about a central cross- sectional axis 314 of the body 302, such that the selective rotational adjustment of the body 302 about the axis 314 enables a different flow adjustment region to be selected for use to control the rate of flow of liquid in the conduit. For example, the peripheral portion 306 is used to define an effective flow aperture that allows the liquid to flow through the body 302 at a particular rate of flow. When the body 302 is rotated about axis 314 to a different position, a different peripheral portion 308, 310 or 312 is used to define a different effective flow aperture, which respectively allow the liquid to flow through the body 302 at different rates relative to the rate of flow for portion 306. For example, portions 308, 310 and 312 may be configured to respectively allow the liquid to flow through the body 302 at 50%, 33% and 25% of the rate of flow through portion 306. Portion 306 may be shaped as a circular weir, and portions 308, 310 and 312 may each be shaped as a V-notch weir.

Figure 4 is a cross-sectional view of the fitting 300 across section A-A shown in Figure 3. The inner length 408 corresponds to the inner diameter of a pipe. The outer length 410 corresponds to the outer diameter of a pipe. The fitting 300 includes an inner flange 402 for engaging with an inner portion of a pipe (e.g. 124 or 112) so as to enable the fitting 300 to attach (e.g. by frictional engagement) to the pipe. For example, the inner flange 402 may have a smaller diameter than the body 404. This enables the outer facing portion of the inner flange 402 to engage with the inner surface of a pipe (at its open end), thus securing the body 302 to the pipe. The inner flange 402 may have a shape corresponding to the cross-sectional shape of the pipe (e.g. 124 or 112), or alternatively, may include an arrangement of one or more flaps extending from the body 302. The fitting 300 may also include an outer flange 404, which provides directional assistance to the flow of liquid towards or away from the opening(s) 306, 308, 310 and 312. The peripheral edge of each of the openings 306, 308, 310 and 312 may include a knife edge 308, which improves the accuracy of the flow rate proportions controlled by the size of the openings.

Measuring small water flows accurately has traditionally been carried out by the use of knife-edge V-notch weirs, as shown in Figure 3. In this case the discharge over the weir, represented as parameter Q (units in m³/s), is calculated by Equation 1 (as described in Webber N. B., 1976, Fluid mechanics for Civil Engineers, Chapman and Hall Ltd):

8 πr

Q = ±j2Ϊ Ci tmZ θ hΛ* Equation 1

where: g is the natural gravitation acceleration (typically = 9.81 m/s²)

C_d is the weir coefficient (typically 0.585) θ is the apex angle of V-notch of the weir (see Figure 3) h is the discharge head over weir, (m)

Consequently where small flows are concerned, the proportion of flows issuing from the a tank are proportional to tan — of the V-notch outlet weir.

In practice, the accuracy of this weir flow equation works best if flow conditions upstream and downstream from the weir are non-turbulent and the weir is not drowned. Consequently, where possible the design of the weir portions 306, 308, 310 and 312, perforated pipe (e.g. 112), outlet pipe (e.g. 126) and holding tank (e.g. 118) should also be constructed for non-turbulent and non-drowned weir flow conditions. Typically, Equation 1 (or appropriate comparable equations) can be used as an aid for designing a suitable weir system for these conditions.

One of the advantages provided by the present invention is the provision of a convenient means of flow control by way of a single fitting 300 having one or more openings for functioning as weirs that can be selectively used to control multiple proportional flows issuing from a holding tank 118. The radial spacing of proportionally shaped/sized weirs at portions 306, 308, 310, 312 allow selective flow control by rotation of the fitting 300. For example, V-notch weirs or . curved weirs can be used, provided that the typical accuracy of flow over the weir is within required tolerances (for example, such that the flow the liquid in the conduit is controlled by one of the weirs relative to the level of the liquid in the conduit). Hybrid weir patterns (which incorporate two or more weir curves) or multiple interactive weirs can also be used to control the rate of flow through the opening(s) of the fitting 300.

Figure 3 shows an example of a body 302 including a combination of different proportionally shaped V-notch weirs at portions 306, 308, 310 and 312, each having a curved weir invert. The narrow inverts of the V-notch weirs (as shown in Figures 3 and 7) often become clogged with debris in the liquid, which in effect, alters the flow characteristics of the weir. This effect is overcome by constructing a wider circular weir with a small radius (R) in the apex of the V-notch (as shown in Figure 3). The design of a fitting 300 that includes multiple weir patterns offers a further advantage in that the eccentric nature of the circular arrangement of weirs (see Figure 3) allows a different weir to be selected for use by rotational adjustment of the fitting 300 relative to the conduit. For example, the incorporation of V-notch weirs allows for small changes of the weir angle by rotation adjustment of the body 302whilst minimising the effect on the accuracy of the weir at small flows resulting from changes in the weir angle (see Figures 3 and 7). The accuracy of the multiple weirs of the fitting 300 may be improved by using small radial weirs (e.g. at portions 308, 310 312) that also have the same flow rate control proportions as the multiple V-notch weirs at portions 308, 310 and 312. For example, best results (for opportunity of adjustment) may be achieved when the head (or level) of the liquid over the weir is about 10% of the radial invert distance (IR) of the weir (see Figure 3).

The invert 316, 318, 320 and 322 of each weir at portions 306, 308, 310 and 312 may be arranged equidistant (i.e. with the same radial invert distance (IR)) from the central cross- sectional axis 314 of the body 302. The weirs at portions 306, 308, 310 and 312 are also spaced sufficiently far enough apart from each other so that different weirs do not interfere with the respective proportional flows. The fitting 300 may have multiple weirs that are radially spaced from each other around the body 302. However, the number of weirs is generally limited by the size of the weir plate and the expected flows over the weirs/ Preferably, as shown in Figure 3, the body 302 includes four weirs at portions 306, 308, 310 and 312.

The weirs at portions 306, 308, 310 and 312 are proportionally sized in accordance with the dispersal requirements of the liquid flow downstream from the holding tank (e.g. 118).

A preferred dispersal arrangement is to have a series of holding tanks (e.g. junction pits)

118, 120 and 122 which in turn distribute the liquid from a source (e.g. a septic tank 104) either to a storage area 106, 108, 110 for its intended use, or to another holding tank 120 and 122 for another serial distribution of liquid, an so on. Other dispersal arrangements are possible, as shown in Figures 10 and 11.

Figure 10 is a block diagram of a dispersal system 1000 in an asymmetric dispersal configuration. The system 1000 distributes effluent from a septic tank 1020 to each of the junction pits 1001, 1002, 1003, 1004 and 1005 in a sequential manner. Each junction pit 1001, 1002, 1003, 1004 and 1005 has at least one outlet for directing incoming effluent into a corresponding absorption trench (e.g. either 1011, 1012, 1013, 1014 or 1015). Some of the junction pits (e.g. 1001, 1002, 1003 and 1004) have a second outlet for directing incoming effluent to another junction pit (e.g. junction pit 1001 has an outlet to junction pit 1002). Figure 11 is a block diagram of a dispersal system 1100 in a symmetrical dispersal configuration. The system 1100 distributes effluent from a septic tank 1120 to each of the junction pits 1101, 1102 and 1103 in a sequential manner. Each junction pit HOl₅ 1102 and 1103 has at least two outlets, each for directing incoming effluent to a different absorption trench (e.g. to 1101 and 1102, 1103 and 1104, or 1105 and 1106). For example, junction pit 1101 directs effluent to absorption trenches 1101 and 1102. Some of the junction pits (e.g. 1101 and 1102) have a third outlet for directing incoming effluent to another junction pit (e.g. junction pit 1101 has an outlet to junction pit 1102).

In this circumstance, the weir proportions, expressed as a percentage (%) of maximum weir flow from each holding tank, are estimated using Equation 2 that describes the proportional weir size on each outlet pipe (identified by a number from 1 to n, where n is an integer) for each holding tank.

Proportional weir size - x 100 Equation 2

where: f_n = relative flow of liquid in the «^th outlet pipe from holding tank (n is an integer). f_m = relative maximum flow of liquid into the holding tank.

With reference to Figure 10, it is desirable to achieve an even distribution of effluent from the septic tank 1020 into the different absorption trenches 1011, 1012, 1013, 1014 and 1015. Thus, assuming the maximum relative flow from the septic tank 1020 is 5 units, and that each junction pit 1001, 1002, 1003, 1004 and 1005 distributes 1 unit of the maximum relative flow to a corresponding absorption trench, the distribution ratio for each junction pit is as shown in Table 1.

Table 1

With reference to Figure 11, it is desirable to achieve an even distribution of effluent from the septic tank 1120 into the different absorption trenches 1111, 1112, 1113, 1114, 1115 and 1116. Thus, assuming the maximum relative flow from the septic tank 1020 is 6 units, and that each junction pit 1101, 1102 and 1103 distributes 1 unit of the maximum relative flow to a corresponding absorption trench, the distribution ratio for each junction pit is as shown in Table 2.

Table 2

From Tables 1 and 2, it can be seen that four distribution ratios are commonly used to achieve the dispersal requirements in each dispersal systems 1000 and 1100 as shown in Figures 10 and 11. The four distribution ratios permit liquid to flow through at about 100%, 50%, 33% and 25% of the maximum relative flow into each junction pit. The fitting 300 shown in Figure 3 enables different distribution ratios to be achieved by having different flow control portions, where at least one of the flow control portions allows a flow rate of approximate 100% (i.e. this is the maximum flow rate proportion issuing from the holding tank, over any time interval), and the preferably the fitting 300 has other flow control portions for allowing a maximum flow rate proportion of approximately 50%, 33% and 25% (relative to the flow control portion allowing a flow rate of about 100%). However, a fitting 300 may have any number of flow control portions, each for allowing a different rate of flow as required.

After the appropriate proportional weir has been chosen from Tables 1 and 2, the fitting 300 is simply slotted into or onto the stub-end of the outlet pipe. The fitting 300 is then rotated so that the invert 316, 318, 320 and 322 of the appropriate proportional weir at portions 306, 308, 310 and 312 is level with the holding tank's ideal common weir outlet level 702 (as shown in Figure 7). In each holding tank, the common weir outlet level 700 is determined by filling the holding tank with liquid (e.g. tap water) to a common weir , . outlet level. ' - ^' "^: "'^

Figure 5 is a cross-sectional view of a junction pit 118 in the on-site sewage dispersal system after installation of flow control fittings to the inlet and outlet pipes, and Figure 6 is a top view of the same junction pit 118. As shown in Figure 5, a drowned end of the pipe baffle 802 is positioned below the surface of the common weir outlet level 700. The flow direction of liquid into and out of the junction pit 118 is indicated by flow arrows D and E respectively. The end portions of the pipes 112 and 126 are fitted with a respective flow control fitting 300a and 300b. The rotational adjustment of each flow control fitting 300 controls the flow in the pipes 112 and 126. For example, the fitting 300 attached to pipe 126 may be adjusted to allow a predetermined flow rate, whilst the fitting 300 attached to pipe 112 may by adjusted to allow liquid to flow through at 50% of the predetermined flow rate.

Figures 8 and 9 show a cross-sectional view and top view of a junction pit 118 in a similar configuration to that shown in Figures 5 and 6. The flow direction of liquid into and out of the junction pit 118 is indicated by flow arrows F and G respectively. The end portions of the pipes 112 and 126 are fitted with a respective flow control fitting 300c and 30Od. As shown in Figure 9, the flow control fitting 300 is fitting to an appropriate pipe bend 902 (or elbow joint). When constructing the holding tank with multiple pipe outlets, the fitting 300 will give best results if the outlet pipes are of a common size and exit from the holding tank with the same invert level. However, this may be difficult to achieve in practice. As shown in Figure 7, the common weir outlet level 700 may be different to the ideal common weir outlet level 702 due to pipe level inaccuracy during construction/installation. The fitting 300 therefore allows easy adjustment in common weir outlet level of about 10% of the radial invert distance (IR) for the weirs at portions 306, 308, 310 and 312 (see Figure 7). For example, as shown in Figure 7, the original position of the body 302 is shown in solid lines, and the body 302 is adjustable by rotation to a second position 302a as shown in dotted lines. Beyond this level of adjustment, more radical level adjustment measures are required. A typical radical measure involves installing an appropriate pipe bend 902 (e.g. a suitable pipe elbow joint) and coupling the fitting 300 onto the appropriate outlet pipe stub end (see Figures 8 and 9). The pipe bend 902 and weir end-cap is typically located on the outlet pipe (or pipes) with the lowest invert level. Pipe bends 902 with larger deflection angles will also accommodate greater levels of adjustment. This arrangement is also suitable for retrofitting suitable junction pits.

If the holding tank is small and is constantly or intermittently filled from an exterior source, then a pipe baffle 802 (eg. a pipe T joint) is installed on the stub end of the inlet pipe to the holding tank (see Figures 5, 6, 8 and 9). The use of a pipe baffle 802 will help to dissipate the directional energy of the inlet flow, and promote more accurate flows of water over the proportional outlet weirs at portions 306, 308, 310 and 312.

The fitting 300 may be made from the materials that are commonly used in the plumbing industry, including PVC, polythene, or polypropylene plastics. The fitting 300 may be mass-produced using an injection moulding process. The weirs at portions 306, 308, 310 and 312 of the fitting 300 can be designed so that it can be fitted into or onto a standard pipe fitting with a water-tight joint (e.g. resulting from the engagement between the inner flange 402 with the inner portion of the pipe, as shown in Figure 4). In the onsite wastewater management industry, 90mm diameter PVC storm water pipes are commonly used to move sewage effluent from the septic tank to the absorption trenches. The present invention may be used to appropriately split and proportion liquid flows issuing from a storage holding tank. This is a common requirement of the onsite sewage management industry, however the present invention may also be used in other industries such as the aquaculture industry. As an example, the present invention is useful for controlling the flow of liquid in a conduit, where the depth of the liquid does not exceed the depth of the proportional weirs at portions 306, 308, 310 and 312 (i.e. the respective ideal common weir outlet level for each weir at portions 306, 308, 310 and 312) in the fitting 300. The flow capacity of each weir can be estimated from Equation 1. The accuracy of the weir flow is typically less than 5% of the estimated flow. The weir system works best if the flow of fluid over the weir is non-turbulent and the weir is not drowned.

The present invention works best when the storage holding tank (e.g. 118) is constructed in accordance with the following preferred features: (i) it is unlikely to move on its foundations (e.g. on a sand foundation bed to minimise ongoing settlement of the junction pit 118, as shown in Figures 5 and 8); (ii) the outlet pipes and holding tank are of sufficient size to promote non-turbulent and non-drowned flow over the weirs (at portions 306, 308, 310 and 312); (iii) the outlet pipes communicating with a particular holding tank (e.g. 118) have the same diameter, and that fits onto/into the fitting 300;

(iv) the outlet pipes communicating with a particular holding tank (e.g. 118) have the same invert level (e.g. 322);

(v) the outlet pipes communicating with a particular holding tank (e.g. 118) have a stub-end that protrudes a sufficient distance into the holding tank (e.g. 118) for the fitting 300 to be slotted onto/into the stub end of the pipe;

(vi) the inlet pipe to the holding tank (e.g. 118) has a T-section baffle 802 (see Figures

5, 6, 8 and 9); and

(vii) the desired proportion of flows issuing from a particular holding tank (e.g. 118) match the weirs provided by the. fitting 300 at each outlet pipe from that holding tank (e.g. 118). Once the above conditions have been achieved the installer, typically a plumber or drainer in the case of the onsite sewage industry, installs the fitting 300 as follows:

Normal Installation Procedure: 1. The contact edge of all fittings 300 are greased for easy rotation adjustment and sealant purposes.

2. The storage holding tank 118 is typically filled with water or other suitable fluid to the invert level of the outlet pipe (e.g. 122 and 126) with the lowest invert level. If the higher constructed invert levels of the remaining pipes are less than 10% of the IR distance (see Figure 7) then the installer continues with step 3. If this is not the case for the invert level 702 of any outlet pipe, then the installer goes to the Radical Installation Procedure (as described below).

3. The installer determines which of the outlet pipes (e.g. 122 and 126) has the highest invert level, and selects the appropriate weir for that outlet pipe (as described with reference to Figures 10 and 11).

4. The fitting 300 is then slotted onto/into the stub end of the outlet pipes (e.g. 122 and 126) and rotated so that the invert level of the selected weir is at its lowest possible level. This invert level setting is designated as the common weir outlet level.

5. The installer appropriately selects the weir settings for the remaining outlet pipes (e.g. 122 and 126) and installs the fittings 300 in the normal fashion so that the invert level of the selected weir is rotated to a level expected to be slightly above the common weir outlet level.

6. The installer fills the storage holding tank 118 up to the common weir outlet level and rotates the selected weir invert levels of all remaining fittings 300 down to the common weir outlet level.

7. The installer checks that every thing is installed at the right level by running some extra fluid into the storage holding tank via the inlet pipe (e.g. 124). Small adjustments in weir level are made where necessary. The weir distribution system is now read for use. Radical Installation Procedure:

1. The contact edge of all fittings 300 and pipe elbow joints 902 are greased for easy rotation adjustment and sealant purposes. 2. The storage holding tank 118 is typically filled with water or other suitable fluid to the invert level of the outlet pipe (e.g. 122 and 126) with the lowest invert level. If the higher constructed invert levels of the remaining pipes are greater than 10% of the IR distance (see Figure 7) then the installer continues with step 3. If this is not the case for the invert level of any outlet pipe, then the installer goes to the Normal Installation Procedure (as described above).

3. The installer determines which of the outlet pipes (e.g. 122 and 126) has the highest invert level, and selects the appropriate weir proportions for those outlet pipes (as described with reference to Figures 10 and 11).

5. The installer appropriately selects the weir settings for the outlet pipes (e.g. 122 and 126) with differential invert levels greater than 10% of the IR distance, and if required, installs a pipe elbow bend 902 and fitting 300 on the outlet pipe stub end in the normal fashion (see Figures 7 and 8). The elbow joint 902 and fitting 300 are both rotated so that the invert level of the selected weir is expected to be slightly above the common weir outlet level.

6. The installer appropriately selects the weir settings for the remaining outlet pipes (e.g. 122 and 126) with differential invert levels less than 10% of the IR distance and installs fittings 300 on the outlet pipes (e.g. 122 and 126) in the normal fashion so that the invert level of the selected weir is rotated to a level expected to be slightly above the common weir outlet level for the outlet pipes (e.g. 122 and 126). 7. The installer fills the storage holding tank up to the common weir outlet level and rotates the selected weir invert levels of all remaining weir end-caps and pipe bends where necessary down to the common weir outlet level.

8. The installer checks that every thing is installed at the right level by running some extra fluid into the storage holding tank via the inlet pipe (e.g. 124). Small adjustments in weir level are made where necessary. The weir distribution system is now read for use.

The present invention provides a number of advantages. Firstly, it allows the relatively complex and timely procedure of setting up proportional outlet weirs in small and large holding tanks (eg. junction pits) to be carried out in a timely and economical fashion by installers with a minimum level of skill. Secondly, the fitting 300 is of a size and nature that lends itself to mass production, hence it is a relatively inexpensive product. Thirdly, within the onsite wastewater management industry this present invention is useful in improving the overall performance of a typical septic tank treatment system. The more evenly distributed effluent will result in higher quality treatment. The treatment will be more aerobic and smell less, the longevity of the treatment system will be increased, and the overall risk to public health and environment will be decreased. Established septic tank systems can also be retrofitted, and thus achieve the same benefits. Consequently, the present invention may provide economic and health advantages to the community.

Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as herein described with reference to the accompanying drawings.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Claims

1. A fitting for controlling the rate of flow of liquid in a conduit, including: a body having one or more openings formed through said body, such that, when said liquid defines a level in said conduit, at least one of said openings is at least partially submerged in said liquid so as to define an effective flow aperture relative to said level for controlling the rate of flow of said liquid through said body; wherein the selective rotation of said body enables adjustment of the size of said effective flow aperture. . ' ! ^■. ■

2. A fitting as claimed in claim 1, wherein said body includes means for coupling said body to an open end of said conduit.

3. A fitting as claimed in claim 1, wherein said body includes means for adjusting the height of said body relative to said level.

4. A fitting as claimed in claim 3, wherein said means for height adjustment includes an elbow joint for coupling with said fitting, said elbow joint also for coupling to said conduit.

5. A fitting as claimed in claim 1, wherein said openings define one or more flow control regions, each said region for defining a corresponding said effective flow aperture of different size relative to said level.

6. A fitting as claimed in claim 1, wherein at least one of said regions defines a said effective flow aperture for allowing a high rate of flow relative to the rates of flow for other said regions.

7. A fitting as claimed in claim 1, wherein at least one of said regions defines a said effective flow aperture for allowing a rate of flow of around 50% of said high rate of flow.

8. A fitting as claimed in claim 1, wherein at least one of said regions defines a said effective flow aperture for allowing a rate of flow of around 33% of said high rate of flow.

9. A fitting as claimed in claim 1, wherein at least one of said regions defines a said effective flow aperture for allowing a rate of flow of around 25% of said high rate of flow.

10. A fitting as claimed in claim 1, wherein said effective flow apertures for said regions are defined by a single said opening.

11. A fitting as claimed in claim 1, wherein said openings define one or more weirs, each said weir corresponding to a different one of said regions.

12. A fitting as claimed in claim 11, wherein each of said weirs is substantially V- shaped.

13. A fitting as claimed in claim 11, wherein each of said weirs includes a rounded weir invert portion.

14. A fitting as claimed in claim 1, wherein each of said weirs includes a knife edge.

15. A fitting as claimed in claim 1, wherein said fitting is made of a plastic material, such as PVC, polythene or polypropylene plastics.

16. A fitting as claimed in claim 1, wherein said body is rotatable along a cross- sectional axis of said body.

17. A conduit including a fitting as claimed in claim 1.

18. A fitting for coupling to an end portion of a conduit for controlling the rate of flow of liquid in a conduit, said fitting including: a disc-like body having an opening formed therethrough, said opening being shaped to form one or more respective weirs, such that, when said liquid defines a level in said conduit, at least one of said weirs is at least partially submerged in said liquid so as to define an effective flow aperture relative to said level for controlling the rate of flow of said liquid through said body; wherein said body is selectively rotatable relative to said conduit to one or more predefined positions, each said position for defining a different said effective flow aperture, wherein said body, in use, is coupled to said conduit in one of said predefined positions. . , . . :

19. A method for controlling the rate of flow of liquid in a conduit using a fitting as claimed in any one of claims 1 to 16, the method including the steps of: i) rotating said fitting relative to said conduit to an orientation that allows one of the one or more openings, of said fitting to form an effective flow aperture relative to the level of the liquid in said conduit; and ii) coupling said fitting to said conduit at said orientation.

20. A method for controlling the flow of liquid through a plurality of conduits using fittings as claimed in any of claims 1 to 16, said method including the steps of: i) rotating each said fitting relative to said conduits to orientations that allow said fittings to form effective flow apertures relative to the level of the liquid in each said conduit; and ii) coupling each of said fitting to said conduits at orientations; whereby the relative flows of liquid through respective conduits is in accordance with a predetermined distribution.

21. A method as claimed in claim 20, wherein at least some of said conduits have the same volume of flow of said liquid.

22. A sewage dispersal system for controlling the flow of sewage through a plurality of conduits using fittings as claimed in any one of claims 1 to 16, wherein said fittings are coupled to said conduits at predetermined respective orientations, said orientations being defined by rotating each said fitting relative to said conduits to allow said fitting to form effective flow apertures relative to the level of the liquid in each said conduit, so that the relative flows of liquid through respective conduits is in accordance with a predetermined distribution.