Patent application title: Sewer Vent
Greg Williamson (Narre Warren North, AU)
Bernie Sizer (Narre Warren North, AU)
ORC Technology Pty Ltd
IPC8 Class: AE03F704FI
Class name: Baths, closets, sinks, and spittoons ventilation sewer
Publication date: 2013-11-21
Patent application number: 20130305441
A sewer vent 1 including structure 3 defining a flow path along which air
entering the sewer travels upwardly past a valve element 4. The valve
element is configured to sink in air to form a seal to prevent gas
escaping from the sewer, and float in water to form a seal to prevent
water entering the sewer.
1. A sewer vent including structure defining a flow path along which air
entering the sewer travels upwardly past a valve element, wherein the
valve element is configured to sink in air to form a seal to prevent gas
escaping from the sewer; and float in water to form a seal to prevent
water entering the sewer.
2. The vent of claim 1 wherein the valve element is or includes a downwardly open vessel portion.
3. The vent of claim 1 wherein the valve element has a waist encircled by the structure to retain the valve element.
4. The vent of claim 3 wherein the encircling structure includes or carries a resilient portion for engaging the valve element to form each of the seals.
5. The vent of claim 1 including an overflow relief mechanism.
6. The vent of claim 5 wherein the overflow relief mechanism includes a mounting arrangement, by which the vent is mountable, configured to permit the vent to be lifted by rising liquid.
7. The vent of claim 6 including a float for lifting the vent.
8. The vent of claim 6 wherein the mounting arrangement includes an upwardly open tube in which the vent is receivable and relative to which the vent may be so lifted.
9. The vent of claim 8 and the upwardly open tube.
FIELD OF THE INVENTION
 This invention relates to a sewer vent.
 Typically urban water systems include two waste streams for carrying waste water away from dwellings: a sewerage system and a separate storm water system.
 The sewerage system includes sewers for conveying waste water from toilets and other bathroom facilities to a treatment facility. This water carries fecal matter and other hazardous materials and is often referred to as "sewage" or "black water". At the treatment facility the sewage is typically treated using a combination of mechanical, chemical and biological techniques to sanitise the water, before the water can be discharged. Typically the treated water is discharged to a natural body of water or watercourse.
 Storm water on the other hand typically receives little, if any, treatment prior to being discharged. By way of example, the storm water may simply be passed through a screen to mechanically separate debris entrained in the water stream. Treating and discharging storm water is thus significantly cheaper than treating and discharging sewage. It is therefore desirable that storm water is not directed into the sewerage system. Storm water entering the sewer is referred to as "infiltration".
 The air within a sewer system is typically pungent with noxious gases. To prevent these noxious gases seeping into dwellings, toilets and other bathroom fittings are fitted with "water traps". A water trap consists of a U-shaped flow path. Water traps are designed so that towards the end of a charge of fluid flowing through the trap (e.g. towards the end of a toilet flushing) air is drawn into the trap and serves to separate an end portion of the charge. The separated charge portion is left behind to fully occlude a lower portion of the U thereby to form a seal to prevent the sewer gases escaping.
 Despite this design intent, fluid moving along the sewer can create a low enough pressure such that the volume of fluid left behind in the water trap is inadequate to form a seal, or even a portion of left behind fluid can be drawn into the sewer. This is referred to as breaking the water trap and results in unpleasant smells emanating from the sewer into the dwelling.
 To address this problem, external vents are sometimes provided. The vents connect the sewer to the atmosphere at a point external to the dwelling. The vents are typically high mounted to minimise the adverse affects of sewer gases emanating from the vent. High mounting the vent also serves to prevent storm water entering the sewer system via the vent, but has drawbacks in that the elevated vent and the plumbing thereto can be unsightly and entails costs.
 Existing domestic sewer systems are typically also fitted with an overflow relief device. Such overflow relief devices are mounted external to the dwelling at a short distance above the ground, e.g. some regulations specify a minimum of 75 mm (about 3 inches), but below the level of appliances internal to the dwelling. Each overflow relief device is connected to the sewer and comes into play if there is a downstream obstruction of the sewer. As sewage builds up in the sewer system to the height of the overflow relief device, it starts overflowing at this point. Thus overflowing sewage is discharged external to the dwelling rather than internal to the dwelling via the appliances.
 The mounting of the overflow relief devices above ground level is intended to prevent storm water entering the sewer via the overflow relief device. This is not entirely effective. If the contour of the ground surrounding the overflow relief device causes storm water to accumulate and puddle about the overflow relief device, once the puddling water reaches the height of the overflow relief device it will enter the sewer. This problem is compounded by the fact that ground contours can change over time. Some nefarious individuals intentionally recountour the surrounding ground (e.g. when a concrete driveway is installed) to direct storm water towards the overflow relief gully when this presents them with a lower cost option than installing appropriate storm water drains.
 It is an object of the invention to provide an improved sewer vent, or at least to provide an alternative for those concerned with sewer vents.
 It is not admitted that any of the information in this patent specification is common general knowledge, or that the person skilled in the art could be reasonably expected to ascertain or understand it, regard it as relevant or combine it in any way at the priority date.
 One aspect of the invention provides a sewer vent including structure defining a flow path along which air entering the sewer travels upwardly past a valve element, wherein the valve element is configured to
 sink in air to form a seal to prevent gas escaping from the sewer; and
 float in water to form a seal to prevent water entering the sewer.
 The valve element may be or include a downwardly open vessel portion. Preferably the valve element has a waist encircled by the structure to retain the valve element, in which case the encircling structure preferably includes or carries a resilient portion for engaging the valve element to form each of the seals.
 The vent preferably includes an overflow relief mechanism, which mechanism may include a mounting arrangement, by which the vent is mountable, configured to permit the vent to be lifted by rising liquid. The vent may include a float for lifting the vent.
 The mounting arrangement preferably includes an upwardly open tube in which the vent is receivable and relative to which the vent may be so lifted.
 Another aspect of the invention provides the vent and the upwardly open tube.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 is a vertical cross-section view of an exemplary sewer vent in situ.
DESCRIPTION OF AN EMBODIMENT
 FIG. 1 illustrates a sewer vent 1 received within an upwardly opened tubular portion 2. The vent 1 and tube 2 are in use mounted close to ground level. The tube 2 is fitted to the end of a pipe which connects to an underlying sewer. The vent 1 is thereby communicated with the sewer.
 The sewer vent 1 includes four principal components: body structure 3, valve element 4, elastomeric ring 5 and float 6.
 The body structure 3 is made up of a top cover 3a, a centre plate 3b and main body 3c. Preferably each of these components is, at least predominantly, formed of PVC. The cover 3a includes a spherically domed portion which presents a convex upper surface and is about 3 mm thick. The cover 3a has a circular periphery when viewed in plan.
 Bosses 3d and 3e, and spigot 3f, project downwardly from an interior of the cover 3a.
 The boss 3d is tubular and mates with a vertical tubular boss 3g extending upwardly from the centre plate 3b to define a vertical through bore communicating a chamber 3h below the centre plate 3b to atmosphere. The upper open end of the boss 3d constitutes an air intake. Desirably the air intake is mounted at, or as in this case adjacent, the very top of the vent 1 to reduce the likelihood of being submerged.
 The boss 3e carries a downwardly open blind bore and mates with a tubular boss 3i projecting upwardly from the plate 3b. A tubular boss 3j projects upwardly from the main body 3c and mates with an underside of the centre plate 3b in alignment with the bosses 3e, 3i. A screw passes through the bosses 3i, 3j to engage the bore of boss 3e to connect the structural members 3a, 3b and 3c.
 The main body 3c includes a circular horizontal base 3k from which an annular wall 3l projects upwardly and a cylindrical wall 3m projects downwardly.
 The base 3k and wall 3l together define an upwardly open cup-like portion. The centre plate 3b sits atop a stop in the form of an upwardly facing annular step on the interior of the wall 3l to define the chamber 3h in the lower half of this cup-like portion.
 The upper edge of the wall 3l defines an upwardly open groove, in which an O-ring is received, and a cylindrical inwardly facing surface. The outer periphery of the cover 3a includes a short downwardly projecting circular rib, co-operable with this cylindrical surface of the wall 3l, and a downwardly facing annular planar surface co-operable with the O-ring. Via this interface the cover 3a sealingly engages the main body 3c.
 As noted, the lower chamber 3h is communicated to the atmosphere via the bosses 3d, 3g. The cover 3a and centre plate 3b together define an upper chamber 3n within the upwardly open cup-like portion of the main body 3c. The centre plate 3b has a central circular aperture through which the lower chamber 3h is communicable with the upper chamber 3n. The centre plate 3b and main body 3c include co-operable tubular bosses (not shown; analogous to the bosses 3d, 3g, which communicate the upper chamber 3n with the region 3o below the main body 3c (which is in turn in communication with the sewer). The structure 3 thereby defines a flow path communicating the outside environment with the sewer.
 The valve element 4 is carried within the central aperture of the centre plate 3b such that any air entering the sewer via this flow path must move upwardly past the valve element 4 en route from the lower chamber 3h to the upper chamber 3n.
 The ring 5 has a square cross-section and an outwardly facing annular groove about its periphery by which it is engaged with the inner edge of the circular opening of the centre plate 3b. The valve element 4 consists of an upwardly open cup-like portion 4a and a downwardly open cup-like portion 4b. In the described vent 1 the portions 4a, 4b are formed separately. A horizontal floor of the portion 4a is bonded to a horizontal ceiling of the portion 4b. The portions 4a, 4b each include outwardly diverging walls defining a waist about the point at which the portions are bonded.
 This waist is encircled by the centre plate 3b and the ring 5 such that the valve element 4 is retained in its position intermediate the lower chamber 3h and the upper chamber 3n.
 In operation of the vent 1, the valve element moves up and down. The spigot 3f is received within the upwardly open cup-like portion 4a at least when the element 4 is in its uppermost position. The spigot 3f co-operates with the internal surfaces of the inclined walls of the portion 4a to limit "cocking" (i.e. to limit rotation about any horizontal axis) of the element 4 as it moves upwardly.
 The inclined wall of the portion 4a carries adjacent its upper edge a sharp annular rib which projects outwardly and downwardly at an oblique angle. When the pressure within the sewer is equal to atmospheric conditions, the valve element will tend to drop to its lowermost position under its own weight. For this purpose the valve element 4 is formed of materials heavier than air.
 In its lowermost position the annular rib of the portion 4a engages the ring 5 to form a seal. This seal serves to prevent air and other gases escaping from the sewer via the flow path of the structure 3. Any increase in gas pressure within the sewer (which would otherwise tend to drive gases from the sewer) tends to drive the valve element 4 downwardly into firmer engagement with the ring 5. Thus preferred forms of the invention have been found to effectively limit the escape of sewer gases.
 On the other hand, a reduction of pressure in the sewer tends to lift the valve element from its lowermost position such that a short "burp" of air enters the sewer to limit the reduction in pressure and in turn preserve nearby water traps.
 The wall of the portion 4b has a stepped profile defining an upwardly facing annular section carrying an upwardly directed sharp annular rib.
 In the event that the vent 1 is submerged, water enters the lower chamber 3h via the bosses 3d, 3g and begins to surround the lower portions of the valve 4. The portion 4b, being a downwardly open vessel, traps a pocket of air. In the described exemplary event, the vent is formed of heavier than water materials and the portion 4b is dimensioned to trap a volume of air sufficient to cause the valve element 4 to float.
 As water continues to accumulate in the chamber 3h, the valve element 4 is lifted until the sharp rib of portion 4b engages an underside of the ring 5 to form a seal. As the depth of water above the vent 1 increases, so does the pressure in the chamber 3h, which pressure serves to drive the sharp annular rib into further engagement with the ring 5. Thus this exemplary vent has been found to be effective to prevent water entering the sewer via the flow path of the structure 3 and thus constitutes an anti-infiltration device.
 As described, the elastomeric ring 5 serves to define the valve element's 4 upper and lower positions and to co-operate with the valve element 4 to form a seal in each of the upper and lower positions. In normal operation, the vent 1 functions as a check valve to prevent gas escaping the sewer and also as a check valve to prevent water entering the sewer.
 The mounting arrangement of the vent 1 will now be described. As will become apparent this mounting arrangement constitutes an overflow relief mechanism.
 The tube 2 has a flared upper end. The outer circular periphery of the cover 3a is dimensioned to sit within and mate with this flared portion. When the vent is so mounted its edges are concealed; only the domed exterior of the cover 3a and its air intake can be reached. These features are not readily gripped by hand. Thus the vent is tamper-resistant.
 An outwardly open annular groove encircles the wall 3l adjacent its upper edge. This groove carries a further O-ring configured to mate with the cylindrical interior of the tube 2 to prevent sewer gases escaping between the tube 2 and the structure 3. The remaining portions of the vent 1 are configured to (at least ideally) clear the tube 20.
 In this example, exemplary vent 1 and tube 2 are configured for a 1.1 mm radial clearance between the cylindrical exterior of the portion 3m and the cylindrical interior of the tube 2. Thus the vent 1 can be simply dropped into the tube 2.
 The float 6 is carried within the region 3o defined by the portion 3m. It also forms part of this exemplary overflow relief mechanism. It includes an upward spigot 6a by which it is mounted to the main body 3c. The spigot 6a is received within and engages a tubular boss 3p projecting downwardly from the centre of the floor 3k. The float 6 is a closed air filled vessel.
 The operation of the overflow relief mechanism will now be described. During normal operation of the sewer the water level is well below the vent 1. In the event of a downstream blockage of the sewer, the water level may rise. In the event that it rises to the level of the float, the float is dimensioned to provide sufficient buoyancy to lift the vent 1. In the described exemplary vent, if the water simply rises to, or slightly above, the level of the float and then recedes, the vent 1 may be lifted a short distance and then dropped to its original position once the water has receded. Thus the vent resets itself without the need for intervention from a user. The elevated vent also serves to provide a visual indication of a blockage before sewage overflows.
 If instead of receding the water in the sewer continues to rise, the vent 1 is lifted further until it projects a sufficient distance beyond the tube 2 to topple therefrom. The vent 1 is thus fully ejected from the tube 2. As the vent 1 is fully ejected, the full bore of the tube 2 is available to provide overflow relief. This reduces the risk of the overflow relief being overwhelmed by a downstream blockage such that sewage overflows from both the overflow relief and from appliances within the dwelling.
 An exemplary vent 1 and tube 2 have been described. This exemplary arrangement should not be construed as limiting the scope of the invention. Other variations are possible. By way of example, it is contemplated that the downwardly open valve portion 4b could be replaced with a lighter than water solid. Whilst it is considered that various lighter than water solids could be workable, the use of a downwardly open vessel is preferred. Various low cost, lighter than water materials are thought to be at risk of various forms of degradation. By way of example, aerated polystyrene is thought to suffer from the interpenetration of various solids which can affect its density.