Abstract:
An apparatus and method for a flow-based fire alarm. A bypass system is provided to allow sufficient water flow where a pressure drop, particularly in a residential or multi-purpose piping system such as a water softener is encountered, by providing an alternate, lower pressure flow path allowing additional flow when the pressure drop through the system becomes too great. Flow detection means are also provided with minimal pressure drop to insure that flow for fire protection need is not unduly restricted. The flow detection means includes either a differential pressure switch coupled to an orifice plate or a moving orifice plate having thereon a magnet, which communicates with a Reed switch in proportion to the flow therethrough. An integral system incorporating all of the elements discussed provides multiple levels of security for a fire protection system for use in a residence or other structure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of Ser. No. 09/098,976 filed Jun. 17, 1998 now U.S. Pat. No. 6,081,196. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the field of fire sprinkler systems. The invention provides an improved apparatus and method for alarming when one or more sprinklers are activated by a fire. In particular, the invention provides a flow detection and measurement means for distinguishing typical domestic water flow from the fire protection flow caused by one or more sprinkler heads. The invention also allows use of a water softener or similar device with a multipurpose piping system (“MPS”) by providing a bypass around the water softener to ensure sufficient water flow for fire protection means. The invention also provides simple and inexpensive devices to measure flow with minimal pressure drop. 
     2. Description of the Prior Art 
     It is well known to provide a means for enunciating an alarm when water flows through a fire protection system. Typical fire protection systems do not have significant water flow therethrough unless a sprinkler head is activated by a fire. Thus, the typical commercial system need only to detect whether or not flow is present, and if so, an alarm must be enunciated. 
     In application Ser. No. 09/098,976 filed on Jun. 1, 1998, for an Apparatus And Method For Multipurpose Residential Water Flow Fire Alarm, a method was disclosed which allows the same piping to be used for both domestic and fire protection needs. The method provided for a flow. detection and measurement means which is capable of distinguishing typical domestic flow from fire protection flow caused by the operation of one or more sprinkler heads. 
     The National Fire Protection Association (“NFPA”) has established standards for the design and operation of multi-purpose residential fire sprinkler systems. The standard is known as NFPA 13D, 1999 Ed. It defines a multipurpose piping system as “[a] piping system within dwellings and manufactured homes intended to serve both domestic and fire protection needs.” 
     Typical commercial fire sprinkler systems utilize a water flow detector to provide an alarm means. When a flow of sufficient, minimal, volume is detected, typical commercial systems indicate an alarm condition. The only reason that water typically flows in commercial systems is activation of a sprinkler head. Therefore, in a typical commercial system an alarm means need only determine whether or not water is flowing. 
     In an MPS water regularly flows through the common piping. Flows occur to supply domestic needs within the residence. Whenever a sink, shower or toilet valve open, water flows in the MPS. Therefore, the alarm system used on typical commercial applications will not work for MPS because simply taking a shower would cause a typical commercial flow detector to alarm when used with an MPS. 
     In light of this problem, typical residential applications have two completely different piping systems: (1) a fire sprinkler piping system, and (2) a domestic piping system. This basically doubles the number of pipes and the amount of plumbing work which has to be performed in a typical residential application. The same set of piping could not previously be used for both systems because the flow alarm would send false signals every time domestic water was turned on. Alternatively, a residential application could use a fire detection system (i.e., electronic fire sensor system). However, a fire detection system does not alarm when water flows. Therefore, with a fire detection system and no flow alarm, the fire sprinklers could run for days, causing extensive water damage, while the home owner is away on vacation and no alarm would sound. 
     As noted above, U.S. patent application Ser. No. 09/098,976 filed Jun. 1, 1998, disclosed an APPARATUS AND METHOD FOR MULTIPURPOSE RESIDENTIAL WATER FLOW FIRE ALARM. The apparatus for use as a multipurpose residential fire suppression water flow alarm system disclosed in that application was comprised of a supply side for delivering water under pressure; a multipurpose piping system having a system side with common piping for delivering water from the supply side to a fire suppression side with one or more sprinkler heads and a domestic side for one or more domestic uses; a detecting means for detecting fire protection flow and for distinguishing that flow from a maximum domestic flow, the detecting means being disposed between the supply side and the system side; a drain test connection; and an alarm means. The method of utilizing the apparatus described above was also disclosed. One of the dependent claims from the above-noted application, claimed a detecting means comprised of an orifice plate through which water flows causing a differential pressure measured by a differential pressure switch so that the flow rate to the orifice plate is proportional to the differential pressure allowing a determination of flow rate based on the differential pressure measured. 
     It was disclosed that the flow detection means could utilize any number of well known flow measurement technologies, such as U.S. Pat. No. 5,288,469 to Otten et al. However, Otten&#39;s device would be less than optimal for the current application because, when fire protection flows are needed, it is desirable to have a flow measurement device which has minimal pressure drop. The Otten device incorporates both an orifice plate and a cone-shaped plug around which the water flows. The cone-shaped plug causes a greater pressure drop than the orifice plate alone. U.S. Pat. No. 5,419,203 to Carmichael discloses a device similar to the device disclosed by Otten. Otten utilizes the Hall effect to measure the displacement of a displacement piston having incorporated therein a magnet. Carmichael utilizes strain sensors to measure the strain caused by displacement of a cone-shaped plug biased by a spring member. As the flow increases, the cone-shaped plug displaces backwardly in reaction to the flow putting greater pressure on the spring and consequently, greater pressure on the pressure sensors incorporated in the device. The Otten and Carmichael devices have several common features, namely a chamber having an orifice plate and a plug-shaped device adapted to be deflected away from the orifice plate in proportion to the flow rate through the chamber. Both Otten and Carmichael have the same primary drawback for use in multipurpose residential systems, namely the substantial pressure drop across these devices. Therefore, there is a need for a flow detection and measurement means for use in an MPS which causes less pressure drop in such a system. At the same time, the means must be simple in both operation and concept so that it will be inexpensive to build and can be easily programed and calibrated in the field. 
     Critics of MPS systems have also noted that it is common for residential systems to incorporate a water softener or similar devices (such as filters, chlorination systems, UV purifiers and the like). Water softeners and similar devices can create substantial drops in system pressure such that the water supply flowing through a typical residential system may not be sufficient for fire protection needs. Therefore, there is a need for a bypass mechanism which will allow sufficient flow in fire protection situations to bypass the water softener to supply the fire protection needs. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a flow detection and measurement means for use in multipurpose residential water flow fire alarm systems which overcome one or more of the disadvantages of the prior systems. 
     In particular, it is an object of the present invention to provide a means to compensate for pressure drops in a typical MPS system. More particularly, typical pressure drops include, but are not limited to, a water softener which may be placed in line in the system. Water softeners are typically used in multipurpose systems to improve the quality of water for domestic use in the residence. In addition to water softeners, pressure drops may include filters, UV treatment of water, and the like. There are many reasons why people want to treat water coming into their homes for domestic purposes. Many of these treatment means will reduce the pressure of the water through the MPS system. Thus, there may be a need for fire protection flows to bypass these pressure drops in the system, or to at least compensate for them. The present invention takes these types of pressure drops into account by providing a bypass means. In typical domestic flow situations, the entire flow of the water supply goes through the treatment method in question, such as a water softener. However, when the system side pressure drops below a set level, a relief allows additional flows through a lower pressure drop path. 
     By the same token, devices previously available for the measurement of flow caused another pressure drop. As noted above, the pressure drops in an MPS system can prevent sufficient flow from being available to satisfy fire protection needs. Therefore, it is also an object of the present invention to provide a volume flow detection and measurement means for use in MPS systems which have minimal pressure drops. The flow detection means discussed are very simple in operation and easy to calibrate in the field. They may be used to provide a read out of the flow, or may simply provide an alarm when fire protection flows are detected. 
     It is also an object of the present invention to provide a flow measurement device with a higher capacity still for use in standard wet pipe systems. Under some circumstances, it may be desirable to use an expanded chamber system along with the orifice plate. In these systems, as the orifice plate is deflected backwardly by the water pressure, it moves into an area of expanded cross-section where the water can flow not only through the center of the orifice plate, but around the edges thereof. This expanded area minimizes the pressure drop through the flow sensor at high demands, such as is the case where multiple sprinkler heads may have activated. 
     It is also an object of the present invention to provide a flow measurement device which can also serve as a back flow prevention device. This objective is accomplished by adding a anti-back flow flap to the orifice plate. As flow proceeds from the supply side to the system side to the orifice plate, the flap is deflected away from the orifice plate allowing flow there through. However, if a back flow condition is created, the flap is deflected back towards the orifice plate, sealing the orifice plate opening. 
     It is also disclosed to incorporate the principal of the anti-backflow flap in a bypass system. In substance, an anti-backflow flap is provided in a flow measurement device with a moving orifice plate. The anti-backflow flap is arranged so as to allow “bypass” flow when the pressure drop through the water softener would otherwise prevent sufficient flow for fire protection needs. Once the pressure drop becomes great enough to activate the anti-backflow flap, the moving orifice plate, which also preferably incorporates differential surface areas on the supply and system sides, begins to be displaced toward the system side of the flow measurement device. A magnet disposed on the system side of the moving orifice plate activates a Reed switch as the flow through the moving orifice plates approaches the fire protection level. As noted with the integral system, another Reed switch for enunciating a trouble alarm may also be provided. 
     Finally, it is an object of the invention to provide a integrated system incorporating the above-noted elements of the invention and having a two-stage alarm for enunciating a pre-alarm, as well as a full-blown fire alarm. The integrated system has two sensors on the flow detection device, the first sensor enunciating a trouble alarm when a specified flow is created, and if the flow further increases, a second sensor enunciating a fire alarm, which also preferably calls emergency response personnel. The first trouble alarm is audible only in the residence or structure where the system is deployed. Preferably, as noted, the second fire alarm will contact emergency personnel, possibly via a telephone modem-type connection. The integrated system also preferably incorporates a tamper trouble alarm on a valve incorporated in the system to shut off the flow thereto. The trouble alarm will enunciate if water flow to the fire protection system is shut off. 
     There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in this application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. Additional benefits and advantages of the present invention will become apparent in those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     Further, the purpose of the foregoing abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientist, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is in illustation of a typical NFPA 13D sprinkler system; 
     FIG. 2 is a prior multi-purpose system, which has no way to alarm; 
     FIG. 3 illustrates an MPS system with a water flow alarm; 
     FIG. 4 is a detail of a differential pressure flow detection means; 
     FIG. 5 is a cross-section of a flow bypass system for use with water softeners and the like; 
     FIG. 6 is a detail of an orifice plate used in the bypass system for flow measurement; 
     FIG. 7 is a cross-sectional view of a differential pressure switch which can be used to measure differential pressure across an orifice plate such as that shown in FIG. 6; 
     FIG. 8 is a cross-sectional view of a residential flow switch with an electronic out put for use in an alarm system; 
     FIG. 9 is a front view of the moving orifice plate used in the above-noted flow sensor; 
     FIG. 10 is a back view of the moving orifice plate, with the orifice plat magnet disposed thereon; 
     FIG. 11 is a detailed view of the Reed switch and adjustable attachment means therefor; 
     FIG. 12 is a cross-sectional view of the Reed switch and adjustable attachment means therefor. 
     FIG. 13 is an illustration of an integrated system incorporating the preferred elements of the present invention for use in a multi-purpose piping system. 
     FIG. 14 is a front view of an orifice plate incorporating the anti-back flow flap. 
     FIG. 15 is a cross-sectional view of the orifice plate incorporating the anti-back flow flap. 
     FIG. 16 is a side view of the orifice plate incorporating the anti-back flow flap in a flow condition where the flap is deflected away from the orifice plate. 
     FIG. 17 is a cross-sectional view of a flow detection means incorporating an increased cross-sectional area to allow additional flow around the periphery of the orifice plate. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A typical NFPA 13D system is illustrated by FIG.  1 . City water or other supply means  10  are connected to a supply system leading into the house. Water first flows through an outside gate valve  12 . The valve  12  is typically integrally connected with a water meter  14 , though the two parts may be completely separate. After flowing through the valve  12  and meter  14  the water passes the exterior wall  16  of the residence. A main control valve  18  is provided in case it becomes necessary to shut off all the water in the house. Though shown inside the residence the main control valve  18  may also be outside of the residence. A pressure gauge  20  is commonly provided to monitor water pressure in the system. A flow splitter  22  divides the water supply into two distinct streams: (a) a fire side  36 , and (b) a domestic side  38 . Following the flow splitter a flow detection means  24  is provided on the fire side  36 . The flow detection means is coupled to an alarm means  26 . Upon detection of flow by the flow detection means  24 , a signal is sent to the alarm means  26 , which creates an alarm condition therein. Piping leads away from the flow detection means to a drain/test connection  28 . The drain/test connection serves two purposes: it allows the fire side  36  to be drained, and it allows for simulation of the flow rate created by the operation of a sprinkler head  30 . Piping also leads away from the flow detection means  24  to at least one sprinkler head  30 . A separate set of piping, the domestic side  38 , leads to one or more domestic uses  32 . 
     It is known that domestic uses of water can have a high enough flow rate to detract from fire protection needs. Therefore, the prior art also discloses a domestic water supply shut-off valve, which is effectively incorporated into the flow splitter  22  for shutting off water supply to the domestic side  38 . Such a shut-off valve is illustrated by U.S. Pat. No. 5,236,002 to Martin et al., and incorporated herein by reference. 
     A typical NFPA 13D system requires two complete sets of piping, both fire side piping  36  and domestic piping  38  to be run throughout the house. These two pipes running side by side require substantial increased material and labor costs to install. Further, for an existing structure, it may be extremely expensive or even impossible to install the second set of piping required for a fire sprinkler system. Given these two problems of additional costs, and the problem with retrofits, a multi-purpose system was envisioned by the NFPA. However, the NFPA provides no means for alarming upon a water flow condition in an MPS. 
     FIG. 2 illustrates the prior MPS. Again, a city or other domestic water supply  10  is provided. The water flows through the outside gate valve  12  and water meter  14  through the outer wall  16  of the residence. Thence the water flows through the main control valve  18 . A pressure gauge  20  is typically provided to monitor water pressure in the system. No flow splitter  22  (shown in FIG. 1) is required for an MPS. A drain test connection  28  is still provided, but there is no flow detection means  24 . As noted above, typical flow detection means  24  alarm upon detection of a minimum flow. Therefore, given the common piping system  40  in the MPS, typical domestic uses would cause the prior art flow detection means to send an alarm signal to the alarm means  26 . NFPA  72  provided for installation of a non-water-flow-based fire detection and alarm system for use with MPS. These non-water-flow-based fire detection and alarm systems are expensive, and they are not capable of detecting flow through one or more fire protection sprinklers. The inability of a fire detection system to detect and enunciate a water flow alarm could result in extensive water damage to the property. 
     FIG. 3 illustrates an MPS system with a water flow alarm. Again a city/domestic water supply  10  is provided. The water flows through the city or outside gate valve  12  through the water meter  14  and past the outer wall  16  of the residence. Once inside the house it passes through a main control valve  18 . As with the prior art multi-purpose residential system described in FIG. 2, common piping  40 , carries water throughout the system. After passing through the main control valve  18 , water passes by a pressure gauge  20 , then through a flow detection means  24 . In combination the flow detection means  24  and the pressure gauge  20  allow for determination of whether the water supply is sufficient for fire protection needs. The flow detection means is connected to an alarm means which is activated upon the detection of a flow rate greater than maximum domestic flow. Methods of detecting and measuring flow and alarming upon excessive flow are illustrated, for example, in Otten, et al., U.S. Pat. No. 5,228,469, incorporated herein by reference. Disposed after the detection means is a drain test connection  28 . This drain test connection  28  serves the same purpose as it did in the prior art (See FIG.  1 ). The drain test connection  28  may include an orifice plate with interchangeable orifice plates for simulating different flow regimes. For example, one orifice plate could simulate the operation of a single fire sprinkler while another orifice plate simulated the domestic usage. These interchangeable orifice plates could then be used to calibrate the operation of the alarm means. Common piping  40  carries water throughout the system to both domestic  32  and fire protection  30  uses. Rather than having distinct fire sides  36  and domestic sides  38 , the invention has short sections of pipe split off from the common piping  40  which are designated as either fire side  36  or domestic side  38 . 
     A means of determining the domestic and fire protection flows will be through the establishment of a “K” values for each. For each flow, the maximum volumetric flow “Q” (usually measured in gallons per minute) is divided by the square root of the pressure “P” (usually measured in pounds per square inch). Thus the formula is as follows:        K   =     Q     P                              
     The greater the “K” value, the greater the flow at any pressure. Typical fire protection “K” values are 4.3 or greater while typical domestic “K” values are 3.3 or less. Thus, the invention takes advantage of the difference in “K” values to distinguish domestic from fire protection flows. The prior art does not anticipate nor suggest that the differing flows for domestic and fire protection uses, as represented by “K” values, could be used as the basis for a flow-based fire protection alarm. 
     The flow detection means  24  could utilize any number of well known flow measurement technologies. See, e.g., Otten et al., U.S. Pat. No. 5,228,469, and Holden, U.S. Pat. No. 5,483,383. 
     FIG. 4 illustrates an orifice plate flow detection system. An orifice plate in the common piping will create a differential pressure which is proportional to the flow rate through the pipe. The orifice plate  42  is disposed within the common piping  40 . An upstream pressure sampling port  44  and a downstream pressure sampling port  46  are connected to a differential pressure switch  48 . The differential pressure between the upstream sampling port  44  and downstream sampling port  46  is proportional to the flow rate through the common piping  40 . The pressure indicated by the differential pressure switch  48  corresponds to a flow rate which can be displayed on an appropriate gauge or digital readout  50 . An alarm output  52  is connected to the alarm mechanism  26  for creating an alarm condition when the flow rate indicated by the differential pressure exceeds some preset value. The drain/test connection could also employ an orifice plate device, preferably accepting interchangeable orifice plates, to simulate the domestic and fire protection demands. The flow could also be measured by a multitude of devices commercially available for detection of flow rate including mass flow meters, pitot tubes, momentum-base flow meters and a multitude of other systems. The orifice plate system is also used in the improved flow measurement means shown in FIGS. 8 through 11, described below. 
     The differential pressure switch  34  shown in FIG. 7 may be used with the bypass system shown in FIG. 5 according to the overall plan shown in FIG.  4 . The differential pressure switch  34  incorporates a first end  74  and a second end  76 . The differential pressure switch  34  also has an inner surface  78  and an outer surface  80 . A first cap  82  is disposed at the first end  74 , and a second cap  84  is disposed at the second end  76 . Both caps have an extended portion  86 . Cap bolts  90  hold the caps against the respective ends. Each end had threaded thereinto a nipple  92  at or near its center. The nipple  92  has a rib  96  on a smooth hose end  94  and a threaded end  98 . A nipple passageway  100  is defined therethrough for allowing fluid communication. A first inlet hose  104  is attached to the smooth hose end  94  by a clamp  102 . Similarly, a second inlet hose  106  is attached to the corresponding smooth hose end  94   b  on the second end. A first membrane  108  is disposed between the first cap  82  and the first end  74 . A reservoir  88  is defined by the first membrane  108  and the first cap  82 . Further, another reservoir is defined by a second membrane  110  disposed between the second end  76  and the second cap  84 . The membranes are fixed in place at their periphery  112  by a clamping action between the ends and the caps as biased by the bolts  90 . A connector  114  attaches a support means  116  to the membranes. A magnet casing  120  is supported by the support means. Incorporated inside the magnet casing  120  is a magnet  118 . A detector means  122  is attached to the inner surface  78 . A first connection  124 , and a second connection  126  are attached to the detector means  122  for carrying the signal created thereby away from the differential pressure switch  34 . 
     As the flow through the system increases, the pressure on the upstream side at a differential pressure switch  34  becomes greater relative to the pressure on the downstream side of the switch  34 . Thus, the first membrane  108  is displaced away from the first end, and the second membrane  110  is displaced toward the second end  76 . This causes the magnet  118 , attached to the support means  116  to be displaced towards the second end, and away from the first end. A magnetic field from the magnet  118  changes the electronic properties of the Reed switch, which is effectively the detector means  122 , as it is displaced towards the second end  76 . Thus, signals are created in the Reed switch  122  indicating that the differential pressure has increased. If the differential pressure continues to increase, at a preset point, an alarm signal is created. 
     Instead of the differential pressure switch described above, it is preferable to use a simple residential flow switch  128  shown in FIGS. 8 through 12 and  14  through  17 . The combination orifice flow meter/displacement magnetic flow sensor  128  incorporates an annular housing  130 . The annular housing  130  will preferably be composed of a non-magnetic, metallic material, such as aluminum. Alternatively, the annular housing may be comprised of a polymer such as CPVC or similar materials. The material of construction is not critical so long as it does not interfere with the operation of the Reed switch. The annular housing  130  has two ends, and at each end a bushing or reducer  132  adapted to be threadedly (or by a socket) attached thereto to allow connection of an inlet pipe at an inlet end  154  of the annular housing  130  and an outlet pipe at an outlet end  156  of the annular housing. A moving orifice plate  134 , having a front face  150  and a back face  151 , is adapted to be received within the annular housing  130 . The annular housing has at least one section with a continuous diameter defined therein for receiving the moving orifice plate  134 . The moving orifice plate has a diameter which is slightly smaller than that of the continuous diameter section of the annular housing  130 , allowing a sliding motion therein, but preventing excess fluid to flow around a periphery of the moving orifice plate. A moving plate opening  136  is defined at or near the center of the moving orifice plate  134 . An orifice plate magnet flange  138  having a diameter larger than that of the moving plate opening  136  is disposed on a back face  151 . Disposed substantially around and outside the flange  138  is a circular orifice plate magnet  140 . The moving orifice plate  134  is biased away from the outlet end  156  by a orifice plate spring  142 . The orifice plate spring  142  is contained between an interior flange shoulder  144  near the outlet end  156 , and the orifice plate magnet  140 . Mounted on an exterior portion of the annular housing  130  is a Reed switch  146 . The Reed switch  146  is attached to the annular housing  130  by an adjustable attachment means  148 . Adjustment screws  152  hold the adjustable attachment means in place and allow it to be loosened for movement of the Reed switch. The adjustable attachment means  148  is shown in detail in FIG.  11  and FIG.  12 . 
     As shown in FIG. 17, the combination orifice flow meter/displacement magnetic flow sensor  128  may have an enlarged section  166  with a cross-section greater than the section with a continuous diameter as noted previously. The purpose of having the enlarged section  166  is to allow additional flow around the edges of the orifice plate as it is displaced backwardly into the enlarged section  166 . Thus, if the flow becomes great enough, the flow may not only proceed through the orifice plate opening  136 , but also around the edges of the orifice plate  134 . A tapered section  164  makes the transition between the area with continuous cross-section and the enlarged section  166 . 
     An anti-back flow flap  168  is shown in FIGS. 14 through 16. The anti-back flow flap is preferably composed of a flexible synthetic polymeric material. The material selected for the anti-back flow flap should be compatible with the fluid flowing through the system, here namely water, so a wide variety of materials may be appropriate. It should have sufficient rigidity so that the flap will not be compressed backwardly through the orifice plate opening  136  if a back flow condition occurs, but sufficiently flexible so that it can deflect away from the orifice plate opening  136  upon a typical flow condition through the orifice plate opening. A flexibility groove  170  is preferably defined in the anti-back flow flap  168  along the length thereof, which allows the flap to more easily deform away from the orifice plate under flow conditions. The anti-back flow flap  168  is attached to the orifice plate  134  by attachment rivets  180 . The anti-back flow flap is shown in a flow condition deformed away from the orifice plate  134  in FIG.  16 . 
     Where a pressure drop is anticipated in a multipurpose system, such as a water softener, the bypass means shown in FIG.  5  and FIG. 6 can be utilized to ensure that adequate flow is provided for fire protection needs. The device causing the pressure drop will be generically referred to as a “flow impediment.” Generally, the bypass means includes a first tee  54  with a water softener outlet and may also incorporate an upstream sample port  44 . Water passing through the water softener outlet goes through the water softener, not shown, and returns to the water softener return  60  in a second tee  56 . Under extraordinary circumstances, where the water demand is greater than can be supplied through the water softener, an alternative flow path is provided. The alternative flow path is comprised of a check valve  62 . The check valve  62  has an annular shoulder  64 . An annular plate  66  is adapted to be biased against the annular shoulder  64  by a tension spring  68 . Alternatively, the surface area of the annular plate could be larger on the system (lower pressure) side than on the supply (higher pressure) side so that it is naturally held in place by the differential pressure. The tension spring  68  is adapted to maintain a sealing contact between the annular shoulder  64  and the annular plat  66  until the pressure downstream of the water softener drops below a specified point. When the pressure drops too low, the annular plate  66  is biased away from the annular shoulder  64  by the differential pressure. A flow path is created there around allowing additional flow through the check valve  62 . Thus, the bypass system provides an alternate, lower pressure drop flow path to ensure that a sufficient flow is provided for fire protection needs, where a flow impediment in the main flow path would otherwise prevent adequate flow for fire prevention needs. 
     Alternatively, the bypass system may incorporate an apparatus similar to the anti-back flow flap  168 , described above. The orifice and flap would have a system side surface area of approximately 1.75 square inches, and the supply side would have a surface area of approximately 0.8 square inches for an approximate 2.25 to 1 ratio. That is, if the pressure on a supply side is 80 pounds per square inch, for example, the orifice plate will remain seated until the pressure on the system side drops to 35½ pounds per square inch. When the pressure drops to this level caused by friction loss, a water softener, or other flow restriction, the orifice flap will open allowing water to bypass the softener or other pressure drop. The pressure differential required to open the orifice flap could be adjusted by varying the surface areas to the desired ratio. Because the differential pressure seats the orifice flap, water is diverted through the water softener until the pressure loss on the system side causes the flow flap to open. This same concept is discussed above, but it is discussed in terms of a rigid plate. 
     It is also anticipated that the bypass system and flow measurement means can be incorporated in a single device. An orifice flow meter/displacement magnetic flow sensor  128  is provided. On the system side, a water softener outlet  58  is provided. A moving orifice plate  134  incorporating an anti-backflow flap  140  on the back side  151  thereof is disposed therein. Both the orifice plate  134  and the anti-backflow flap  140  have larger surface areas on the system side than the supply side. Preferably, the ratio of supply side to surface side is the same for both the plate  134  and the flap  140 . Once the ratio of supply to system side pressures exceeds the surface area ratios, the anti-backflow flap  140  will open up and allow flow through the opening  136  and the moving orifice plate  134  will begin to be deflected toward the system side by the differential pressure. 
     As shown, the bypass system may incorporate a flanged fitting  70  incorporating flange o-rings  71  and flange bolts  72  to house an orifice plate  42 . The orifice plate  43  itself may include a downstream sample port  46 . In addition, the flanged fitting  70  may incorporate a pressure gauge port  73 . After passing through the flanged fitting  70 , the water supply goes to either domestic needs or fire protection needs. FIG. 6 provides a detailed cross-sectional drawing of the orifice plate  43  housed in the flanged fitting  70 . 
     Preferably, the system includes a pressure gauge  20 . Applicable standards specify a minimum volumetric flow rate at a specified residual pressure. In combination, the flow detection means (K) and the pressure gauge  20  (P T ) enable determination of whether the water flow rate through the system is sufficient to supply fire protection flow rates. 
     
       
         Q=K{square root over ((P T +L ))} 
       
     
     To reiterate, the problem to be solved by the present invention is provision of a water-flow-based means of alarming an MPS. In the past, such systems had to utilize two completely different piping systems: one for domestic uses and one for fire sprinkler system uses. Previous alarms used in these systems were designed to create an alarm condition upon the detection of a flow (commonly 10 gpm). Typical domestic flows would have caused an alarm in a prior art system. Alternatively, prior art systems used a fire detection and alarm system which did not have a flow detector. These systems without a flow detector risked substantial water damage to the structure if a sprinkler head activated while no one was in the home. 
     The present system is based on the principle that domestic flow rates are much lower than flow rates needed for fire protection. Using a flow detection means  24  (FIG.  3 ), it is possible to create an alarm condition only upon detection of flows which are such as created by fire protection needs. Thus, an alarm condition is not created when typical domestic uses only are detected. 
     FIG. 13 shows the system incorporating the features disclosed herein. The system shown in FIG. 13 is an MPS system, but it could be that instead of incorporating domestic demands, the system could simply supply fire protection needs, in which case it would be more like a standard sprinkler system. A water supply means  10  supplies water through a gate valve  12  and a water meter  14  to the exterior wall  16  of the structure. The water enters the system through a main control valve  18 . Preferably, as shown, the main control valve  18  will have a tamper protection means  158  for determining whether the valve is closed, and if so, enunciating a trouble alarm. A pressure gauge is also preferably provided in the system. Water then flows through a combination orifice flow meter/displacement magnetic flow sensor  128 . The sensor  128  shown has two normally open Reed switches disposed thereon for detecting flow as indicating by displacement of the moving orifice plate  134 , not shown. The first Reed switch  146  is the same as previously disclosed, and enunciates a fire alarm via the fire alarm means  26 . Preferably, the Reed switch  146  also activates a system which contacts emergency response personnel, such as fire departments. In addition to the fire alarm Reed switch  146 , the present invention incorporates a first stage Reed switch  160 . The first stage Reed switch  160  enunciates a first stage trouble alarm  162 . Preferably, the first stage trouble alarm  162  is only enunciated within the structure (i.e., emergency response personnel are not contacted) The alarm is created when the domestic usage is excessive. Where the system is used with an MPS, the first state alarm will cause anyone in the residence to instinctively shut off water, for example a shower they may be taking. As another example, if a resident hears a first stage alarm, and they were washing dishes, they will most likely shut off the sink faucet. This natural reaction to the first stage alarm may reduce the water flow demand below the level where the first stage alarm enunciates, eliminating the alarm condition. As can be seen in FIG. 13, the first stage Reed switch  160  is displaced a slight distance, shown as delta “d,” toward the inlet  154  of the flow sensor  128 . Thus, as the moving orifice plate is displaces towards the outlet end  156  of the flow sensor  128 , it will first activate the first stage Reed switch  160 , enunciating the internal first stage trouble alarm  162 . As the orifice plate  134  continues to be displaced towards the outlet end  156 , it will next activate the fire alarm Reed switch  146 , which enunciates the alarm means  26 , preferably notifying emergency response personnel. The delta “d” (i.e., the linear displacement of the fire alarm Reed switch  146  and the first stage Reed switch  160 ) will be set in the field so that there is sufficient differential in the flow which activates the first stage alarm and the fire alarm to give residents or occupants of the structures sufficient time to shut off domestic demands before a fire alarm is created. This two-stage system also serves as a safety back up, because if one of the alarm stages fail, the other will still alert residents to the potential alarm condition. 
     Tamper detection means  158  on the main control valve  18  preferably incorporates Reed switches as well. As the handle is turned, a magnet on the handle activates a normally open Reed switch to close, enunciating an alarm notifying the occupants of the structure that the valve has been closed, and the fire protection system is not being supplied with water. Again, this is an important safety consideration in residential systems where small children, unknowing homeowners, and the like can easily turn off the system without realizing they are shutting off their fire protection system as well. 
     Though the invention has typically been described with reference to a multi-purpose piping system, it should be understood that the system could be used with any flow-based alarm system for fire protection. Further, the flow detection means disclosed herein could be used with any flow system, not just fire protection systems. That is, the flow detection means are capable of detecting the flow of any fluid through a piping system. The piping system could carry hydrocarbons, solvents, or any other liquid or potentially gaseous materials for that matter. 
     OPERATION 
     In operation the apparatus functions as both a domestic water supply system and a fire detection and alarm system. Under normal conditions, the water flow rate through the flow detection means  24  does not reach the fire suppression flow rates. When one or more sprinkler heads  30  activate, the flow detection means  24  detects the increased flow and sends an alarm to the alarm means  26 . The alarm means  26  enunciates a visible or audible alarm indicating the alarm condition. It is well known in the prior art to activate a telephone modem-based system for calling, for example, the fire department, upon detection of an alarm condition. See, e.g., Otten, U.S. Pat. No. 5,139,044. It will be preferable to incorporate such a modem-based component in the present invention to notify the fire department and other emergency contacts should an alarm condition be detected. If one or more domestic cutoff valves  48  are included in the apparatus, the flow detection means  24  also sends a signal to activate the domestic cutoff valves, shutting off water to one or more domestic uses  23 . 
     The method for calibrating the apparatus includes the following steps: (1) opening the drain/test connection to simulate a minimum fire protection flow rate caused by the operation of one sprinkler head; (2) setting the flow detection means  24  to create an alarm output when a flow rate just below the minimum fire protection flow rate is detected by the detecting means; (3) insuring that an alarm condition is created when a minimum fire protection flow rate is detected by opening the drain/test connection  28  and checking for an alarm condition; and (4) insuring that an alarm condition is not created with maximum domestic flow by simulating the maximum expected domestic flow, then checking for an alarm condition. As noted, the drain/test connection  28  can be adapted to receive different orifice plates to simulate different flow regimes. Preferably, there would be one orifice plate to simulate minimum fire protection flow and a second orifice plate to simulate maximum expected domestic flow. Where the drain/test connection  28  accepts interchangeable orifice plates, the calibration of the flow detection means  24  is greatly simplified. An operator simply inserts an orifice plate for simulating fire protection flow, then calibrates the flow detection means  24  to enunciate an alarm at a slightly lower flow rate. The operator then ensures that an alarm condition is created at the fire protection flow rate. Next, the operator replaces the orifice plate designed to simulate minimum fire protection flows with one designed to simulate maximum domestic flow. Finally, the drain/test connection  28  is again opened to ensure that an alarm condition is not created at maximum domestic flow rates. 
     When the system of FIG. 13 is provided, it is necessary to calibrate both the first stage trouble alarm  162  and the first stage Reed switch  160  by means similar to that noted above for the single stage fire alarm  26  and Reed switch  146 . The preferred method is to first calibrate the fire alarm Reed switch  146 . The calibration is very simple. First, the drain test connection is opened to simulate fire protection needs, the connection means for the Reed switch  146  are loosened, and it is moved towards the inlet end  154  of the sensor  128  until an alarm condition is created. The first stage Reed switch  160  will then be moved a slight distance further towards the inlet end  154 . A typical domestic demand is then created by using the drain test connection  28  or flowing water from some number of plumbing fixtures. As the flow through the drain test connection approaches the highest end of the expected domestic demand, the first stage Reed switch  160  should be activated, activating a first stage trouble alarm  162 . If the alarm is not activated, the first stage Reed switch  160  is moved further towards the inlet end  154  of the sensor  128 . 
     To calibrate the differential switch  34  shown in FIG. 7, the first and second inlet hoses  104  and  106  respectively, are attached to sample ports upstream and downstream respectively of an orifice plate. A flow is then created which equals the largest expected domestic flow through the MPS. Either the position of the magnet  118  or the Reed switch  122  is adjusted until no alarm condition is caused by the maximum domestic flow. The minimum fire protection flow is then simulated. Again, the magnet  118  or the Reed switch  122  are moved until an alarm sounds. Maximum domestic flow is repeated to ensure that no alarm is enunciated upon maximum domestic flow, and once this is accomplished, the device is calibrated. In addition, it may be desirable to calibrate the differential pressure switch to create an output signal proportional to the flow rate. This would allow connection of the output signal to an electronic gauge to provide a read out of the actual flow rate through the MPS. In such case, flow rate readings are taken from at least two points. The flow rate readings are entered into an electronic system for creating a flow read out proportional to the signal created by the differential pressure switch. Systems of this type are disclosed, for example, U. S. Pat. No. 5,228,469 to Otten et al. 
     The detection means shown in FIGS. 8 through 12 is calibrated similar to the above-noted process for the differential pressure switch. However, the combination orifice flow meter/displacement magnetic flow sensor  128  incorporates both the flow measurement means as well as the orifice plate in one device. An orifice plate  134  is selected with an opening  136  appropriate for the flow rates expected. The orifice plate  134  is inserted into the annular housing  130  as shown in FIG.  8 . That is, the back face  151  faces the outlet end  156 . The orifice plate spring  142  is trapped between the moving orifice plate  134  and the orifice plate magnet  140 . As with the differential pressure switch, the maximum domestic flow and the minimum expected fire protection flow are then simulated, and the Reed switch is adjusted to provide the appropriate outputs at the above-noted flow rates. As shown, the annular housing  130  may have sample ports for a pressure gauge  20  and a flow gauge  50 . The flow gauge  50  provides a direct read out of the flow rate through the orifice plate. 
     While the invention has been shown, illustrated, described and disclosed in terms of embodiments or modifications which it is assumed, the scope of the invention should not be deemed to be limited by the precise embodiment or modification therein shown, illustrated, described or disclosed. Such other embodiments or modifications are intended to be reserved especially as they fall within the scope of the claims herein appended.