FIELD OF INVENTION

This invention relates to a gas evacuation device. More particularly, this invention relates to a gas evacuation device for a water chamber. Still more particularly, this invention relates to a gas evacuation device for removing gas from a chamber or an electrolytic cell in line with a water pump.

BACKGROUND ART

The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.

Water pump systems having a chamber in line with a water pump, are known to suffer from the inefficiencies caused by air becoming trapped in the chamber. Of particular interest to this invention are water pump systems where the chamber outlet is on the vacuum side of the water pump. Particular problems occur where the chamber is of a particular configuration and/or dimension such that the water flow through the chamber cannot remove all of the air contained therein. Accordingly air increasingly becomes trapped at the top of the chamber thereby adversely affecting performance of the water pump system.

Water cleaning systems may include a strainer or leaf filter chamber on the suction side of a pump. Generally pump flow rates are matched to that of the strainer or filter chamber, such that air is not normally trapped within the chamber. However, in recent times the pool industry has adopted larger strainers as a practical tool and for marketing purposes. This has caused a discrepancy between the relative flow rates of the strainer or filter chamber and the pump and has led to an emerging problem of air entrapment in the strainer or filter chamber. No-one has solved this air entrapment problem to date, despite a long-existing problem of reduced performance of such filter chambers where air entrapment occurs.

The provision of variable speed pool and spa pumps has also created an air entrapment problem for certain types of electrolytic cells located on the pressure side of a pool filtration system. This is particularly the case where the electrolytic cell is set at a low speed whereby some cell chambers tend to accumulate air pockets due to the slow water flow rate.

Debris strainers or filters are typically located prior to a water pump to protect the latter. Such strainer or filter chambers may be deliberately limited in size, to induce turbulence in the water flow to flush air from the chamber. An air-free strainer or filter chamber is important to maximise the surface area of the strainer or filter contained within the chamber. If the water flow through the chamber is insufficient to flush all of the air out of the chamber, the trapped air will effectively reduce the surface area of the strainer or filter and thereby reduce efficiency. The applicants have considered reduced performance of debris strainers or filters to be a significant problem and have sought to provide a solution

In the swimming pool and spa industry, strainer or filter chambers may be provided on the vacuum side of the pump, including chambers forming an integral part of the pump. Such chambers may have a transparent lid to enable an operator to inspect the strainer or filter at any time without the need to switch the pump off. If the operator determines that the strainer or filter is sufficiently full to limit water flow through the chamber, the transparent lid may be removed and the strainer or filter cleaned. A large sized strainer or filter (and correspondingly large sized chamber) is desirable because there will be greater capacity to hold debris, thereby reducing the frequency required for cleaning the chamber. That is, the greater the volume of debris a chamber will hold before it begins to limit water flow, the longer the system is adapted to operate between cleans.

However, the corollary to this is the inappropriate manufacturing practice in which strainer or filter chambers are provided that are physically too large or configured in such a way that the design of the chamber does not facilitate the complete removal of air from the chamber by the flushing action of incoming water. If air trapped within the top of the chamber extends low enough so that the strainer or filter is not completely submerged in water, the surface area of the strainer or filter is limited thereby reducing its capacity to hold debris. ^'

The trapped area below the top of the transparent lid of the chamber also has the negative affect of obscuring the view of the strainer or filter, thereby obviating the utility of the transparent lid.

Apart from the negative functional aspects of having air trapped in the upper portion of a strainer or filter chamber, the effect of the trapped air is considered in the pool and spa industry to be aesthetically undesirable. That is, installers, representatives of the service industry for pool and spas, as well as consumers, are not comfortable with the visual impression caused by the trapped air. The provision of larger sized chambers has great benefits, provided all of the air can be removed from the pre-pump chamber.

An object of the present invention is to ameliorate the aforementioned disadvantages of the prior art or to at least provide a useful alternative thereto. STATEMENT OF INVENTION

Accordingly, in one aspect of the invention there is provided:

A pool or spa filter chamber having a strainer or filter, the chamber for connection in line to the negative pressure side of a water pump and for receiving water flow through at least one inlet port and exhausting the water from the chamber through at least one outlet port, the chamber including a gas passage having at least one mouth for receiving gas from an upper region of the chamber, a section for conveying the gas and at least one opening for exhausting the gas into the outgoing water stream at a delivery region at or adjacent the outlet port, the pressure in the upper region being higher than at the delivery region. The chamber may form part of a pool or spa filtration and pump system. The system may include an electrolytic cell chamber on the positive side of the water pump. The electrolytic cell chamber may be inline with the water pump. The electrolytic cell chamber may include a second gas passage for receiving gas from an upper region of the electrolytic cell chamber and conveying the gas to the outgoing water stream at or adjacent the outlet port of said electrolytic cell chamber.

Accordingly, in another aspect, the invention provides:

An electrolytic cell chamber for a pool or spa filter system, the chamber for connection in line to the positive pressure side of a water pump and for receiving water flow through at least one inlet port and exhausting the water from the chamber through at least one outlet port, the chamber including a gas passage having at least one mouth for receiving gas from an upper region of the chamber, a section for conveying the gas and at least one opening for exhausting the gas into the outgoing water stream at a delivery region at or adjacent the outlet port, the pressure in the upper region being higher than at the delivery region. The gas may include any of a variety of gases such as air, hydrogen, etc. Typically, a pool filter chamber may receive partially dissolved air. Bubbles may enter the influent line from a pool skimmer or other inlet or catchment means. For example, when the pool or spa is in use and splashing or waves occur, air pockets may be introduced into the influent line, especially if the pool or spa water level locally and momentarily dips below the inlet. Leaking pipes and connections between devices in the filtration system may allow air to enter the lines.

The gas passage is defined as having three parts. A mouth adapted to receive gas and other fluids from the upper region, an exhaust opening from which the gas or other fluids is dispensed from the gas passage, and a conveying section extending between the mouth and the opening that allows the gas to be conveyed from the upper region to the delivery region without its flow being interrupted.

The gas passage conveying section comprises a tube or conduit having any suitable cross section, such as circular, oval-shaped, square or other polygonal. Alternatively, the conveying section may form part of the sidewall of the gas passage. For example, the conveying section may be concave or arcuate in shape and may have a pair of spaced and opposed sidewalls that generally follow the contour of the inside or outside surface of the chamber sidewall. Preferably, the conveying section is generally hollow- cylindrical in shape .and has a circular or oval-shaped cross section whereby the side walls are resistant to collapse under external pressure. Preferably, the gas passage comprises a tube or conduit that is non-collapsible when exposed to the pressure differentials typically associated with pool and spa filter chambers. The gas passage may be made from a range of suitable materials, such as polymeric, ceramic or metallic materials, or a combination of the foregoing, noting that resistance to chlorine degradation is preferred and, for longevity, necessary.

The gas passage may be located inside or outside the chamber and may even be incorporated in a sidewall of the chamber. In another arrangement, the gas passage may be integrally formed with the chamber structure, for example through a unitary molding process. Alternatively, the gas passage may be retro-fitted to any existing chamber. The gas passage may be located inside or outside the chamber.

The gas passage may be retro-fitted to the chamber. For example, where the gas passage extends, at least partially, outside the chamber, the inlet mouth may be located in the upper region internally with the chamber. The conveying section may extend through a hole formed in the wall of the chamber and may continue externally down to a portion of the chamber sidewall. The conveying section may again enter the chamber so that the exhaust opening can be positioned at or adjacent the outlet port within the chamber. Alternatively, the exhaust opening may be located in an effluent pipe immediately following and in communication with the outlet port so that the conveying section does not re-enter the chamber. In a particularly preferred arrangement, the gas passage is attached to, or incorporated with, a strainer or filter. The strainer or filter may be removable from the chamber whereby the gas passage may be cleaned at the same time as the strainer of filter. In the case of an electrolytic cell chamber, the gas passage may be removably attached to the internal wall of the chamber, for example by brackets, or may be attached to one or more cell plates. In any case, it is preferred that the gas passage be removable from the chamber to facilitate cleaning thereof.

At least one mouth of the gas passage may comprise a widened end to facilitate smooth and unimpeded flow of a water/gas mixture into the gas passage and may thereby be bell-shaped. Alternatively, the mouth portion of the gas passage may comprise a cage or mesh structure whereby to admit gas/liquid, but to prevent ingress of debris. Accordingly, the mouth may include a simple strainer, such as a mesh cover extending across the mouth. This may simply comprise a patch of mesh or strainer material of a flexible consistency, such as polymeric or corrosion-resistant metal mesh, which may be secured to the external wall of the gas passage by a rubber ring, metal tie or the like.

The gas passage may include multiple mouths whereby to locate openings to the gas passage at more than one location in the chamber. For example, the chamber may include more than one high point or upper region in which gas, such as air, may collect.

The gas passage may, indeed, comprise more than one conveying section and the conveying sections may or may not be in communication with one another. For example, the gas passage may comprise two or more tubes that independently convey gas from the upper region to the delivery region. The gas passage may include more than one opening for exhausting the gas into the outgoing water stream. For example, the gas passage may include one exhaust opening located internally within the chamber and another exhaust opening that is fed into the effluent pipe connected to the outlet port. The advantage in including multiple gas passage lines is to obviate blockages in one or more of the gas passage lines. However, preferably the gas passage comprises a single conveying section and only one mouth for receiving gas and a single exhaust opening.

The gas passage may include a means to create negative pressure in the delivery region compared to the upper region. For example, the exhaust opening may include a turbulence inducer. The turbulence inducer may be incorporated in the structure of the exhaust opening. The turbulence inducer may be a structural feature of the exhaust opening that causes the effluent water stream to be diverted past the region immediately adjacent the exhaust opening. For example, the turbulence inducer may comprise a lip or bead formed in the end wall of the gas passage. Alternatively, the turbulence inducer may be in the form of a transverse inclined cut to the end of the gas passage, the opening facing away from oncoming water flow to form a pressure depression at the opening. Advantageously, the preferred arrangement utilises a Venturi affect to enhance the pressure depression at the exhaust opening by utilising fast water flow past the exhaust opening.

Accordingly, unlike prior art filter arrangements where water is typically forced into a filter chamber from a pump whereby the chamber is located on the positive pressure side of the pump, in the present strainer or filter chamber, the chamber is located on the negative pressure side of a water pump so that water is drawn through the outlet port inducing water flow through the chamber and, ultimately, through the inlet port. Because water is induced to flow through the strainer or filter chamber, water flow through the outlet port and in the delivery region is fast and takes advantage of the Venturi affect in inducing flow of the water/gas mixture through the gas passage. This is in contrast with prior art arrangements where water is forced through the inlet port so that advantage cannot be made of the chamber being located on the negative pressure side of the pump. The present arrangement therefore greatly improves the performance of the gas passage by enhancing the pressure differential and increasing gas evacuation rates from the upper region.

The chamber may include one or more inlet ports and one or more outlet ports. However, preferably, the chamber includes a single inlet port and single outlet port. The chamber may be a strainer or filter chamber and may include a strainer basket, sand or diatomaceous earth filter core, or a synthetic or paper filter. Preferably, the strainer or filter chamber is adapted to receive a removable strainer or filter basket or cartridge.

The chamber may comprise a lid above or adjacent the upper region. The lid may be removable or attached, such as by a hinge means. The lid includes a water and airtight seal when properly fitted. The upper portion of the chamber, optionally including the lid, may be configured whereby the chamber upper region corrals the gas towards a gas pocket to facilitate collection of the gas for removal through the gas passage. The removable lid may therefore have an internally concave surface or dome shape whereby gas tends to rise to the uppermost internal region of the chamber corresponding to the upper region. Alternatively, the chamber or upper portion may be configured to permit multiple air pockets adapted for removal by multiple air passage mouths. Preferably, the at least one mouth is uppermost in the chamber whereby the gas cannot permanently collect above the mouth. However, where the gas passage, by virtue of sufficient pressure differential and or the Venturi affect, is drawn down into the mouth and does not permanently collect above the mouth, the mouth may be situated immediately under the upper region whilst remaining effective. BRIEF DESCRIPTION OF THE DRAWINGS Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. In the drawings: Figure 1 is a perspective view of a pump and filtration system for a pool or spa according to a first embodiment;

Figure 2 is an exploded perspective view of a filter chamber according to one embodiment of the present invention;

Figure 3 is a schematic side section view of a filter chamber and water pump according to a second embodiment;

Figure 4 is a schematic side sectional view of a pool filter and water pump according to a third embodiment;

Figure 5 is a schematic side sectional view of a filter and water pump according to a fourth embodiment; Figure 6 is a schematic side sectional view of a filter chamber according to a fifth embodiment;

Figure 7 is a schematic side sectional view of a water chamber according to a sixth embodiment;

Figure 8 is a schematic side sectional view of a water chamber according to a seventh embodiment;

Figure 9 is a schematic side sectional view of an electrolytic chamber according to an eight embodiment;

Figure 10 is a schematic side sectional view of an electrolytic cell chamber according to a ninth embodiment; Figure 11 is a schematic side sectional view of an electrolytic cell chamber according to a tenth embodiment;

Figure 12 is a schematic side sectional view of an electrolytic cell chamber according to an eleventh embodiment;

Figure 13 is a schematic side sectional view of an exhaust opening of a gas passage according to another embodiment; Figure 14 is a schematic side sectional view of an exhaust opening of a gas passage according to yet another embodiment;

Figure 15 is schematic side sectional view of an exhaust opening of a gas passage according to still another embodiment; and

5 Figure 16 is schematic side view of an exhaust opening of a gas passage according to yet another embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to Figures 1 and 2, there is shown a pool filtration system comprising a centrifugal pump 10 driven by an electric motor, a sand filter 20 and a coarse strainer o filter chamber 30.

The electric pump 10 causes water to flow into the strainer filter chamber 30, through the strainer basket 31 whereby large debris particles, such as hair, leaves, twigs and the like, are captured. The water flow then enters the electric pump housing, flows through an impeller, out the pump discharge port, through a connecting hose 11 and into a filter5 control valve 21. Dirt is collected in the sand filter 20 as water is directed by the control valve 21 downward onto the top surface of the filter sand bed contained in the filter 20.

Clean water flows through lower piping out the bottom of the sand filter 20 and up through a return pipe, back into the control valve 21. Clean water returns through the pool return hose 22 to the pool or spa 5. A backwash may be performed periodically to0 clean the sand filter 20 by adjusting the valve 21 and removing water borne lint and sediment through the waste pipe 23. During operation, the strainer filter basket 31 collects debris up to the point where water flow through the chamber 30 is sufficiently low to effect performance. The strainer filter chamber 30 includes a transparent lid through which an operator may view the contents of the strainer basket 31 whereby to5 determine whether the strainer basket 31 is due to be emptied. The lid 32 is sealably attachable to the main chamber canister 33 and sealable by means of a rubber O-ring 34. The chamber canister 33 includes a drain hole 35 closable by removable stopper 36, and influent port 37 and effluent port 38. The influent port 37 is connected to a body of pool or spa body 5 and the effluent port 38 is connected to the electric pump 10 on its0 negative pressure side. Accordingly, it can be seen that water is drawn from the pool or spa body 5 through a pipe 39 into the influent port 37.

Retro-fitted to the basket 31 is a gas passage in the form of a plastic tube 40. The tube 40 extends from the upper end of a basket handle 41 down to a position intermediate the length of the basket 31 body. The coveting section 51 of the tube is held onto the basket 31 by plastic ties 41. When the basket 31 is replaced in the canister body 33, the tube 40 is positioned so that its receiving upper end mouth 42 is positioned at the upper region of the closed strainer chamber 30. The lower end of the tube 40 terminates in an exhaust opening 43 that is positioned in the delivery region adjacent the outlet port 38 when the strainer basket 31 is correctly installed in the chamber canister 33.

Turning to Figures 3-8, various embodiments are shown of strainer filter and other chambers located on the negative pressure side of a water pump.

In Figure 3, a strainer filter chamber 30a is connected via pipe 44a to the negative side of a water pump 10a. The strainer chamber 30a includes a strainer canister 31a having side flanges 45a and act as holding brackets for an air passage tube 40a. The electric motor 10a induces flow of water through pipe 44a, in turn through outlet port 38a, canister body 31a and influent port 37a as shown by water flow arrows W. Water borne debris 46a collect in strainer basket 31a. The gas phase of turbulent water entering from the influent port 37a collects in the upper region 47a of the chamber 30a. As water flows past the exhaust opening 43 a, negative pressure is created immediately adjacent the exhaust opening in a delivery region via the fast moving water W. This has the effect of drawing the water/gas mix phase in the upper region 47a into the tube mouth 42a. This evacuates air or other gases from the upper region 47a expels them into the delivery region 48a. There it is dissolved and dispensed in the water flowing through to the electric pump 10a through the pipe 44a.

Referring to Figure 4, there is shown a third embodiment in which the air passage 40b is integrally formed by molding or retrospectively attached to the internal sidewall 49b of a filter chamber 30b. The gas passage 40b may be in the form of a tube or cylinder, or may be of arcuate shape along its length whereby it is comprised of spaced and opposed sidewalls that generally follow the contour of the sidewall 49b. The gas passage 40b in one embodiment is an annular sleeve forming the internal wall of the chamber.

In Figure 5, an air passage 40c is external to a filter chamber 30c. The air passage 40c is a plastic or metal tube or pipe. The air passage 40c may be retro-fitted to the chamber 30c by drilling a hole in the upper sidewall 49c of the chamber 30c and attaching the mouth 42c to the hole. The hole is then sealed at the connection by a fitted rubber washer or sealant. Similarly, the exhaust opening 43 c may be connected to the pipe 44c connecting to the electric pump 10c by similarly creating an aperture and sealable connecting the exhaust opening to the pipe 44c. The sealed connections for the mouth 42c and exhaust opening 43 c must be air and water tight to ensure that they are not themselves the source of contamination of air into the system. Turning to Figure 6, there is shown a filter chamber 3Od in which the canister lid 32d is dome shaped and internally concave. The chamber 3Od houses a fitted air passage tube 4Od that is configured to follow the line of the sidewall 49d. The tube 4Od extends at its upper end centrally to terminate at its mouth 42d at an upper region 47d centrally in the chamber 3Od. The mouth end 42d of the air passage 4Od is flexible whereby to permit the canister basket 33d to be removed without impedance. It is also sufficiently rigid so as to be non-collapsible when subjected to typical pressure differentials experienced between the upper region 47d and the delivery region 43 d. The exhaust opening 43 d is fed through the exhaust port 38d and partially extends into the pipe 44d communicating with a pump (not shown). It will be appreciated that the internally concave shape of the domed lid 32d causes any gas in the chamber 30d to collect at the upper region 47d whereby to mitigate against the permanent collection of gas at the upper region 47d.

In Figure 7, a water chamber 3Oe is shown having a hinged lid 32e that is inclined to the horizontal when sealably fitted on the upper portion of the chamber 3Oe so that any gas contained in the chamber 3Oe tends to collect at the upper region 47e. By positioning the air passage mouth 42e in the upper region 47e, the collection of gas thereat is minimised. The seventh embodiment shown in Figure 8 is similar to that shown in Figure 7, except that a hinged chamber lid 32f is provided with a raised portion 50f that encourages any gas in the chamber 3Of to migrate to an upper region 47f to form a temporary air pocket whereby any air collected in the upper region 47f is evacuated by an air passage 4Of.

The application of this method of providing a tube 40 with a pressure differential across it to facilitate the movement of air out of the chamber 30 can also be applied to electrolytic cell chambers 60 utilised in swimming pools and spas. Although these are on the pressure side of the filtration system 1, the positioning of the tube ends 42,43 such that a pressure differential exists across the tube 40 will be effective in eliminating the entrapped air. The high pressure end 42 of the tube 40 must be uppermost in the cell 60 and the low pressure end 43 is located at or near the exit port 63 of the cell chamber 60. The low pressure end 69 of the tube 40 may require modification to induce a vacuum as a result of venturi action.

The increase in variable speed pumps in the pool and spa market has highlighted that at lower than normal flow rates through many electrolytic cells, the cell cavity is not filling 100% with water. Trapped air is preventing flow detectors from operating or electrode plates from being 100% submerged. This is leading manufacturers to dangerously suggest cells be inverted such that the air is more easily flushed from the cell cavity.

The air evacuation tube may also extend from the high to low pressure areas on the outside of the cell chamber. Referring to Figure 9, there is shown an electrolytic cell 60 having a plurality of cell plates 61, an influent port 62 and an effluent port 63. Inserted in the electrolytic cell 60 and extending between an upper region 64 and the effluent port 63 is an air passage tube 65. The tube 65 is adapted to remove gas that collects in the water-filled internal space of the chamber 60 by similar hydro-dynamic processes as described with reference to Figures 1-8 in relation to the first to seventh embodiments. The difference in this arrangement is that the influent port 62 is generally connected by a pipe 66 to the positive pressure side of a water pump (not shown), rather than on the negative pressure side. In Figures 10 and 12, there is shown an electrolytic cell 60a,b having a single air passage 65a,b with multiple mouths 67a,b for ingress of gas in the upper region 64a,b of the chamber 60a,b. The air passage 65a,b comprises a single tube or pipe with mouth openings 67a,b spaced along an upper length 68a,b extending along the upper region 64b. The air passage 65a,b terminates at its lower end at an exhaust opening 69a,b. The exhaust opening 69a,b is positioned in a delivery region 70a,b in the exhaust port 63a,b of the chamber 60a,b. The effluent port 69a,b is connected to the positive pressure side of a water pump (not shown).

Referring to Figure 11, there is shown an electrolytic cell chamber 60c similar to the ninth and eleventh embodiments shown in Figures 10 and 12, respectively, with the exception that a pair of air passages in the form of tubes 65ci,cii are used to evacuate air or other gases from two upper regions 64ci,cii. The pair of tubes 65ci,cii convey the gas/water phase mixture to a delivery zone 70c at or adjacent the exhaust port 63c.

As shown in Figures 13-16, the exhaust opening 43, can be configured to develop a venturi affect as water flow W streams past the exhaust opening 43, thereby creating a delivery region A having lower pressure than the upper region 47, 64. This is achieved by providing a turbulence inducer that is either inherent in the structure of the exhaust opening 43. Examples of this are shown in Figures 13, 15 and 16. The exhaust opening 43 faces away from the oncoming water flow W. This creates a negative pressure delivery region A at or adjacent the exhaust opening 43. In Figures 14 and 16, the turbulence inducer is in the form of an inclined opening 43. The angled opening 43 effectively extends into the path of oncoming water flow W to create an impendence. The angled opening 43 thereby creates turbulence in the delivery region A. However, even a simple normally transverse exhaust opening 43 g shown in Figure 15 is sufficient to create a negative pressure effect in the delivery region A. This is because the air passage wall 7 Ig closest to the predominate water flow W still has the effect of impeding the water flow in the delivery region A. This creates negative pressure in the delivery region A.

In Figure 14, the function of the turbulence inducer is effectively achieved by a small lip or bead 72h that extends into the path of oncoming water flow W to reduce the water pressure in the delivery region A. The air passage 40,40a-f, 65a-cii has an internal diameter along its length sufficiently large to allow removal of air trapped in the chamber. Applicants have found that a tube diameter of 2 - 20mm is effective and not prone to occlusion. However, the actual optimum diameter will be determined by structural and dimensional considerations such as the chamber volume, the distance travelled in moving the air from the upper region 47a to the delivery region 48a, the pressure differential between the two regions 47a,48a and the rate of water flow W. In a particularly preferred arrangement, an internal tube diameter of 5mm was sufficient to provide an effective air passage. Advantageously, the mesh size of the filter basket or other filtering medium or barrier is less than the internal gas passage diameter so that any debris that might evade the filtration medium does not block or otherwise restrict the operation of the air passage 40,40a-f, 65a-cii.

The air passage 40,40a-f, 65a-cii may include an internal flow enhancer. For example, the air passage 40,40a-f, 65a-cii may include an impeller 82 to facilitate flow of fluid from the upper region. The air passage 40,40a-f, 65a-cii may include a unidirectional valve 81 to prevent backflow up the air passage 40,40a-f, 65a-cii from the delivery region.

The Applicants identified that a tube with an internal diameter of 5mm positioned within a chamber that suffers with entrapped air effectively provided a conduit for the transfer of this trapped air to the water exist port of the chamber. The pressure or vacuum differential between the tube ends effectively provided for the movement of the air.

The location or design of the tube 40 is not limited to the examples given as this invention provides for a conduit for the air via the application of a pressure/vacuum differential across the tube 40. As stated above, a tube 40 with an internal diameter of 2mm to 20mm may be effective in the removal of trapped air within the chamber 30 although smaller or larger diameters may be effective depending on location and tube end designs.

An upper end of the tube 40 is located uppermost in the chamber 30 to ensure all or most of the air can be removed. This end of the tube 40 as the high pressure or low vacuum end 42. In prior art arrangements, this end would be the high pressure end of the tube connected to the high pressure side of a pump. The other end 43 of the tube 40 is located at or near the port 38 at which the water exits the chamber 30 ..This end 43 of the tube 40 is the low pressure or high vacuum end. The closer that the low pressure end 43 of the tube 30 was positioned to the water exit port 38 of the chamber 30, the greater the pressure differential across the tube 40 and therefore the greater the speed of air evacuation. Modifying the low pressure end 43 such that a greater venturi is formed speeds up the air removal.

Preferably the internal diameter of the tube should be such that it will not suffer blockage but be of a size that is practically fitted or integrated within the chamber. A filter or strainer may also be provided on the high pressure side of the tube to prevent blockage.

The tube may be provided on the strainer or filter itself. When the strainer or filter is fitted into the chamber, the tube is located such that a pressure differential is established and becomes effective in the air removal.

The tube may also be fitted such that the path from the high pressure end to the low pressure end transverses outside of the chamber itself.

The reference numerals used to describe features shown in the drawings are generally listed below, noting that duplication has been avoided where like features are described with reference to like numerals:

Throughout the specification and claims the word "comprise" and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word "comprise" and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise.

Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper' and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the mouth uppermost.

It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention.