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These portions may be part of a continuous pipe, but more typically and for ease of understanding in the example, the description of the system 32 hereof refers to pipes which are fluidically interconnected as part of a stack. Thus, the wet stack portion of the four stacks A 5 B, C and D have respective wet stack discharge pipes 1 , 6, 14 and 19 which deliver discharges from the system to the sewer 34, and feed pipes 2, 7, 15 and 20 which deliver water to the wet stack discharge pipes 1 , 6, 14 and 19 respectively from respective discharge sources 46, 48, 50 and The feed pipes 2, 7, 15 and 20 each include respective U-shaped traps 54, 56, 58 and The discharge sources 46, 48, 50 and 52 are also referred to herein as Aappliances and are illustrated as water closets, also known as toilets or commodes, but it may be appreciated that these sources may include a variety of plumbing hardware or fitting items, such as by way of example but not limitation, floor drains, sinks, shower stalls, bidets, water fountains or the like.

Each stack A, B, C and D further includes wet stack upper pipes 3, 8, 16 and 21 which are located just above the junctions where the feed pipes connect to the stacks, dead end pipes 4, 9, 17 and 22, and upper pipes 5, 10, 18 and The wet stack upper pipes and the dead end pipes are considered herein as part of the wet stack portion of the stacks, and the upper pipes 5, 10, 18 and 23 are considered dry stack pipes, meaning that typically only air and not liquid is typically held therein and communicated therethrough.

The upper or dry stack pipes may be directly or indirectly fluidically coupled for connecting each of the respective stacks A, B, C, and D at an upper level, i. While such connection means may be a direct connection of one dry stack pipe to another, more typically an interconnecting member is used to fluidically connect the stacks at an upper level. Such an interconnecting member or means may be a pipe, hose or fitting, and is here illustrated as a common pipe or manifold 11 which fluidically connects the stacks and extends upwardly for connection to other connectors for ventilation.

In the illustration of the system shown in Figs. Because both the AAV and PAPA are designed to be positioned either within the ambient atmosphere or within a closed environment, the T fitting 62 and the pipes 12 and 13 may be located above the roof 72 of the building Thus, in the system 32 of Fig. While the positioning of the PAPA 68 and the AAV 70 at the upper end of the system 32 is a preferred arrangement of these components, it is to be understood that the invention hereof contemplates other placement options for the PAPA 68 and AAV 70 within the system For example, one or a plurality of the AAVs 70 may be located at alternate locations such as adjacent and fluidically connected to the traps 54, 58, 60 and 62, or one or more PAPAs could be installed proximate the stacks A, B, C and D by the use of a diversion pipe fluidically connected to the stack, including positioning the diversion pipe for connection to the wet stack portion.

Positioning the PAPA 68 and the AAV 70 at these alternate locations within the building 30 would still fulfill the goal of providing air to the system 32 from controlled sources.

Fler böcker av John Swaffield

In the system 32A, however, the T fitting 62 is removed and the PAPA 68 is connected either directly to the common pipe 11 or by a further pipe or the like. A connector pipe 74 is then provided between the PAPA 68 and the AAV 70 which, as in system 32, is able to receive air from the ambient atmosphere or, as illustrated, from an accessible loft space to provide an enclosed, sealed building source of air to the AAV One AAV 70 useful in accordance with the present invention is shown in U.

Such an AAV broadly includes a valve body 76 having a lower part comprising a normally vertical tubular member 78 adapted to be connected to a pipe including a common pipe or manifold as described above which is part of a sanitary discharge and ventilation system. The upper end of the tubular member 78 has a conical shaped restriction 80 which is closed at its extremity. The conical upper portion 80 of the tubular member 78 is provided with two diametrically opposed passages 82 each of which has a moulded- in grid 84 to prevent the entry of strange objects, such as animals or insects.

The conical upper portion 80 of the tubular member 78 is surrounded by an oblong bowl-shaped housing 88, extending upwards from the tubular element 78 and having an upper edge 90 which is situated about a horizontal plane crossing the upper extremity of the conical portion 80 of the tubular member The space between the bowl-shaped housing 88 and the conical portion 80 of the tubular member is subdivided by a partition 92 into mutually opposed orthogonally arranged pairs of first and second chambers.

The first pair of chambers are delimited by the partition 92 and closed sections 94 of the conical portion 80 and are in communication with the surrounding atmosphere via openings 96 in the bowl-shaped housing The second pair of chambers are delimited by the partition 92 and the bowl-shaped housing 88 and are in communication with the lower tubular member 78 via the passages 82 in the conical portion 80 of the tubular member The upper edge of the partition 92 is located about the horizontal plane and is configured so as to form a valve seat A valve member is carried on the upper edge of the partition 92 and is normally seated on the valve seat 98 to isolate the first pair of chambers from the second pair of chambers when the internal pressure in the system 32 or 32A is at least equal to the atmospheric pressure.

The valve member is lifted or elevated above the valve seat 98 in response to a lowering of the internal pressure below the atmospheric pressure to thereby place the first pair of chambers in communication with the second pair of chambers, thus admitting atmospheric air into the system 32, 32A connected to the lower tubular member The valve member and the corresponding valve seat 98 preferably have a butterfly-shaped form which is positioned in a longitudinal direction inside the oblong bowl-shaped housing The openings 96 in the bowl-shaped housing 88 are also provided with a grid to avoid interference between the valve member with any foreign object.

The closed extremity of the conical portion of the tubular member 78 is provided with a closed cavity extending downwards and being arranged as a fixed female guiding means for the valve member which is, for that purpose, provided with a projection movable male guiding member having similar dimensions as the cavity The main or inner part of the valve member is of hard plastic or the like, while the peripheral border part is made of a soft plastic material to seal with the valve seat The valve body 76 is closed with an upper lid which encloses the upper edge in a tight manner by slightly conical normally downwardly extending side walls Patent Application No.

Such a PAPA 68 comprises an external casing 1 14, a housing 1 16, a flexible reservoir 1 18 and an end cap The flexible reservoir 1 18 is sealed against the housing receiving end and the housing remote end by the AO ring compressing a layer of sealant not shown. This allows the flexible reservoir to operate without any leakage. The housing receiving end and the housing remote end are linked together by means of separator plates leaving between them open spaces in contact with the flexible reservoir 1 The external casing 1 14 fits partly over the housing 1 16 and over the flexible reservoir 1 The external casing 1 14 has a plurality of means of ventilation , such as openings, shown for example in Fig.

These means of ventilation allow the flexible reservoir 1 18 to be in permanent contact with the atmospheric air at atmospheric pressure whilst preventing the flexible reservoir 1 18 from being damaged by any external event. A graduated connector may be provided for attaching the PAPA 68 to, e.

The graduated connector allows the connection of at least two different sized pipes together in a secure manner, and may be made of an elastomeric material. The housing 1 16 includes a remote section which leads to the housing remote end , a receiving section which extends remotely from the housing receiving end , and the separator plates which allow airflow to continue through the PAPA when the flexible reservoir is fully collapsed. The separator plates do not extend fully around the circumference of the housing , but rather provide gaps between the separator plates allow air from the drainage and ventilation system 32 or 32A to enter the flexible reservoir 1 18 and inflate the latter in the case of positive pressure within the system 32 or 32A, thus absorbing the energy of any transient pressure wave.

In complex building drainage systems, the operation of the system is designed to accommodate the discharge of water into the system by various appliances such as the discharge sources 46, 48, 50 and Multiple discharge sources are typically provided in a discharge network or system, and their operation is almost always entirely random.

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As a consequence, these discharge sources provide conditions which result in air entrainment and pressure transient propagation, which are entirely random. No two systems will be identical in terms of their usage at any time. This diversity of operation implies that inter-stack venting paths will be established if the individual stacks within a complex building network are themselves interconnected.

The present invention takes into account this diversity and utilizes it to provide system venting and a sealed drainage and ventilation system 32 or 32A. To provide a most preferable sealed building drainage and ventilation system 32 or 32A as illustrated herein, negative air transients in the system would be alleviated by drawing air into the network from a secure space providing either purified or segregated air, rather than from the external atmosphere.

CPD Article: High-Rise Drainage Ventilation

This may be provided by the use of AAVs 70 positioned to deliver air to the system at locations adjacent the discharge sources 46, 48, 50 and 52, or from a purifying mechanism, or at a predetermined location within the building, such as an accessible loft space as an alternative to being located in the ambient atmosphere above roof Similarly, to provide such a preferable sealed building drainage and ventilation system 32 or 32A, it is necessary to attenuate positive air pressure transients by means of PAPA devices 68 mounted within the building envelope.

While it might be considered that this would be problematic, positive air pressure could build within the PAPAs and therefore negate their ability to absorb the positive air pressure arising from transient airflows within the system. This problem is largely addressed in the present invention by linking generally upright stacks in a complex building and thereby utilizing the diversity of use inherent in building drainage systems.

Such diversity helps to ensure that pressure transients delivered to PAPA devices 68 are themselves alleviated by allowing trapped air to vent through the interconnected stacks and downward into the sewer The present invention also utilizes the complexity of the system 32 or 32A to protect the system 32 or 32A from sewer driven overpressure and positive transients. The larger bore size of the sewer 34 advantageously ensures that adverse pressure conditions will thereby be distributed among the stack piping and the network interconnection will continue to provide venting routes.

The AIRNET simulation of system operation provides local air pressure, velocity and wave speed information throughout a network at time and distance intervals as short as 0. In addition, the AIRNET simulation utilized in the example hereof replicates local appliance trap seal oscillations and the operation of active control devices, thereby yielding data on network airflows and identifying system failures and consequences. The example is illustrated with reference to system 32 as shown in Fig. Water downflows in any stack generate negative transients which typically deflate the PAPA 68 and open the AAV 70 to provide an airflow into the system Positive pressure generated by either stack surcharge which, as used herein, includes introduction of liquid into a stack or sewer transients which, as used herein, involves increases or decreases in pressure arising from an event in the sewer such as fluid flow, a drop in liquid volume in the sewer, or an increase in liquid volume in the sewer are attenuated by the PAPA and by the diversity of use that allows one stack-to-sewer route to act as a relief route for fluid in other stacks.

In the example of the system 32 illustrated in Fig.


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Each of the bases is preferably connected to the respective stack independent of the connection between the other bases and the sewer. Pressure transients generated within the network will propagate at the acoustic velocity of air, i. In the context of the system 32 as illustrated herein, this implies pipe periods, which is the round trip travel time of a pressure transient from stack base to a PAPA 68 of approximately 0.

Heriott watt report Building Drainage and Vent systems

In the example of the system 32, which is a simplified illustration of a complex building drainage and ventilation system used in the example hereof, no local trap seal protection is included, that is, while the traps 54, 56, 58 and 60 in the present example do not have active transient controls such as AAVs or PAPAs, such could be provided at the traps. Traditional networks as known in the art could include passive venting where separate vent stacks would be provided to the atmosphere.

Also, as shown in Fig. In a complex building this arrangement would not be arduous and would in all probability be the norm. In the present example, the pipes 1 , 3, 6, 8, 14, 16, 19 and 21 are all considered wet stack pipes. Each of the pipes 1 through 10 and 1 1 through 23 are 0. Pipes 5, 10, 18 and 23 are 6 meters in length in the present example. Again, as described above, while the illustration of the system in Figs. Further, in the example hereof: discharges from discharge sources 46, 48 and 50 are water closet.

It is believed that in this example in the system 32, the water flows within the network simulate actual system values, being representative of current water closet discharge characteristics in terms of peak flow being about 2 liters per second, overall volume about 6 liters, and duration of discharge being about 6 seconds. The sewer transients in the present example are at 30 mm water gauge pressure, which are representative but not excessive.

Heights for the system stacks A, B, C and D are measured in a positive manner upward from each stack base. Thus, entrained airflow towards the stack base is shown as a negative value, and airflow upward is shown as a positive value. Airflow entering the system 32 or 32A is therefore indicated with a negative value, and airflow exiting the system to the sewer 34 is indicated as a positive value, and airflow induced to flow up a stack will also have a positive value.

Water downflow is indicated with a negative value. Water Discharge to the System. Referring now to Fig.

Transient Airflow in Building Drainage Systems

However, the entrained airflow in pipe 19 is into the system 32 from the sewer Initially, as there is only the minimum flow, essentially a trickle, in pipe 19, the initial entrained airflow in pipe 19 due to the discharge sources 46, 48, 50 already being carried by pipes 1 , 6 and 14, is reversed, that is, up the stack D. This initial entrained airflow in pipe 19 contributes to the entrained airflow demand in pipes 1 , 6 and The AAV 70 connected to pipe 12 further contributes to the entrained airflow demand, but initially this is a small proportion of the required airflow and as seen in Figure 6.

Further, the valve member of the AAV 70 may flutter in response to local pressure conditions.

Following the discharge source 52 discharge to stack D that establishes a water downflow in pipe 19 from the time period at 2 seconds onward, the reversed airflow initially established diminishes due to the traction applied by the falling water film within the pipe However, the suction pressures developed in stacks A, B and C still reults in a continuing but reduced reversed airflow in pipe As the water downflow in pipe 19 reaches its maximum value from 3 seconds onward, the AAV 70 connected to pipe 12 opens fully and an increased airflow from this source may be identified as shown in Fig.

The flutter activity of the valve member is replaced by a fully open period from 3. The air pressure in stack D demonstrates a pressure gradient compatible with the reversed airflow mentioned above. The air pressure profile in stack A is typical for a stack carrying an annular water downflow and demonstrates the establishment of a positive backpressure due to the water curtain at the base of the stack A.

Following completion of the discharges of water from discharge sources, the airflows will naturally attenuate over a period of time based on the frictional resistance in the system As a minimum or trickle flow is assumed to continue in each stack, the rate of attenuation of the entrained airflows is low. The initial collapsed volume of the PAPA 68 installed on pipe 13 was 0.

However, due to its relatively small initial volume it may be regarded as collapsed during the phase of the example illustrated in Fig. Surcharge at the Base of Stack A. The entrained airflow in pipe 1 reduces to zero at the stack base and a pressure transient is generated within stack A as illustrated in Fig.

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The impact of this transient will also be seen later in a discussion of the trap seal responses for the system It will also be seen from Fig. That is to say, a small positive back pressure as the entrained air is forced through the water curtain at the base of each stack and into the sewer is shown. In the case of stack D, Fig. Utilizing the AIRNET simulation practice allows the air pressure profiles up stack A to be modeled during and following the surcharge illustrated in Fig.

The traces illustrate the propagation of the positive transient up the stack A as well as the pressure oscillations derived from the reflection of the transient at the stack termination where the upper end of pipe 1 1 joins to the T fitting Sewer Imposed Transients. Figure 1 1 illustrates the imposition of a series of sequential sewer transients at the bases , , and of the pipes 1 , 6, 14 and 19 for each stack A, B, C and D 5 respectively.

As the positive pressure is imposed at the base of pipe 1 at 12 seconds, airflow is driven up stack A towards the PAPA 68 connection to pipe However, as the bases , and of the other stacks B, C and D have not yet had positive sewer pressure levels imposed, a secondary airflow path is established downwards to the connections to sewer 34 at the bases , and in each of stacks B, C and D, as shown by the negative airflows in Fig.

As the imposed transient abates, so the reversed flow reduces and the PAPA 68 discharges air to the system 32, again demonstrated by Fig. This pattern repeats as each of the stacks is subjected to a sewer transient. Diversity implies that simultaneous sewer transient imposition would not be a likely condition and one that would be prudently avoided by ensuring connection to several sewer outlets here shown at bases , , and In a complex building arrangement, the provision of a plurality or multiplicity of such connections to the sewer 34 should not present an issue.

The pressure gradient in stack B confirms that airflow direction up the stack towards the T fitting 62 where pipes 12 and 13 lead respectively to the AAV 70 and PAPA It will be seen that pressure continues to decrease down stack A until the pressure recovers in lower portions of the stack A at pipes 1 and 3. This is due to the effect of the continuing waterflow in pipes 1 and 3.

The use of the PAPA 68 in the present example reacts to the sewer transients by absorbing airflow. Studor, who employ 9 people to market these devices, have increased turnover [text removed for publication].


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  7. The team has enabled and enhanced the development of unsteady flow simulations to model the wastewater and air pressure regimes within building drainage networks. Since , our research has concentrated on the development of methods and technologies to support system integrity in building drainage networks. Should system integrity become compromised, the resulting linkage made between the miasma present within the drainage network and the habitable space occupied by the building user can, depending on circumstances, adversely affect public health due to the possibility of cross-contamination — a causative factor in the Amoy Gardens SARS outbreak in Hong Kong.

    Following an extensive programme of EPSRC-funded research [G1,G2,G3], carried out during the mid-to-late s, it became evident that although the focus of the design engineer had, to date, been on the prevention of excessively high negative pressures introduced as a result of appliance downflows, the positive pressures generated within a system were of a magnitude that could present significant risk to system integrity [1]. Around this time, Swaffield, Campbell and Jack were alerted to a number of trap-seal loss problems experienced in high-rise high-density residential accommodation in Hong Kong.

    Identification of this problem confirmed the relevance of application of the group's numerical simulation model, AIRNET, to problems of this type.