Patent Publication Number: US-2023151975-A1

Title: Tankless water heater isolation valve assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 17/314,819, filed May 7, 2021, entitled TANKLESS WATER HEATER ISOLATION VALVE ASSEMBLY, which claims priority to and the benefit of U.S. provisional patent application Ser. No. 63/024,571, filed May 14, 2020, the contents of each application being incorporated herein by reference in their respective entireties. 
    
    
     FIELD OF THE APPLICATION 
     The application relates to isolation valve assemblies, particularly isolation valve assemblies for tankless water heaters. 
     BACKGROUND 
     Tankless water heaters heat a cold water flowed into the tankless water heater inlet and provide an on demand heated water from the tankless water heater outlet. One common tankless water heater preventive maintenance is to flow a mild acid such as a food grade vinegar through the internal pipes and heat exchanger to prevent buildup of deposits that could degraded efficiency of the tankless water heater, or even cause a system failure. However, it is important to not introduce the cleaning solution into the water system, typically a potable water system including home hot water systems. Therefore, isolation valve assemblies are provided which allow for the tankless water heater inlet and outlets to be isolated from the cold water feed and hot water supply lines during cleaning operations. 
     SUMMARY 
     The foregoing and other aspects, features, and advantages of the application will become more apparent from the following description and from the claims. 
     In one illustrative embodiment, an isolation valve assembly comprises a valve body defining a first fluid port and a second fluid port opposing the first fluid port and at least one drain port disposed between the first fluid port and the second fluid port, an isolation valve disposed within the valve body and a handle operatively coupled to the isolation valve. The handle is movable to cause corresponding movement of the isolation valve between a first normal position where the isolation valve fluidly couples the first fluid port and the second fluid port, and a second drain position where the isolation valve fluidly couples the first fluid port and the at least one drain port and isolates the second fluid port. 
     In embodiments, the isolation valve defines a fluid passage. The first fluid port comprises a fluid inlet port and the second fluid port comprises a fluid outlet port. The isolation valve may include an outer plug seal portion at least partially circumscribing the fluid passage where the outer plug seal portion is configured to seal the fluid outlet port in the second drain position of the isolation valve. The handle may be mounted for rotational relative to the valve body whereby the handle is rotatable to cause corresponding rotation of the isolation valve between the first normal position and the second drain position. A drain valve assembly may be mountable adjacent the at least one drain port of the valve body. The at least one drain port may include a first drain port and a second drain port opposing the first drain port. A removable plug seal may be disposed within one of the first drain port and the second drain port. The drain valve assembly may be mounted adjacent the other of the first drain port and the second drain port. The handle may be repositionable between first and second rotational orientations relative to the valve body to enable right or left hand movement of the handle to effect corresponding rotation of the isolation valve between the first normal position and the second drain position. 
     In certain embodiments, the valve body includes a pressure relief port. The pressure relief port may define a fluid relief path and the first and second drain ports define respective first and second fluid drain paths. The first and second drain ports may be positioned relative to the valve body whereby the first and second drain paths intersect the relief path. 
     In other embodiments, the first and second drain ports may be positioned relative to the valve body whereby the first and second drain paths do not intersect the relief path. 
     In embodiments, the fluid inlet port may be coupled to a tankless water heater. 
     In other embodiments, the isolation valve may be configured to fluidly couple the drain port with the first fluid port and the second fluid port when in the first normal position. 
     In another illustrative embodiment, a method, comprises: 
     coupling a fluid inlet port of a valve body of an isolation valve assembly to a tankless hot water heater; 
     rotating a handle of the isolation valve assembly to a first handle position to cause corresponding rotation of an isolation within the valve body to a first valve position to fluidly couple the fluid inlet port with a fluid outlet port of the isolation valve assembly; 
     rotating the handle of the isolation valve assembly to a second handle position to cause corresponding rotation of the isolation valve within the valve body to a second valve position to fluidly isolate the fluid second outlet port from the first inlet port; and 
     when in the second handle position of the isolation valve, activating a drain valve assembly coupled to at least one drain port of the valve body to drain fluids delivered from the tankless water heater to drain the fluids. 
     In embodiments, the method may further comprise activating a pressure relief valve coupled to a pressure relief port of the valve body to relief pressure associated with the fluids. 
     In certain embodiments, the method may further include mounting the isolation valve assembly to one of first and second opposed drain ports of the valve body and sealing the other of the first and second drain ports. 
     In other embodiments, the method may further include enabling the handle to be repositionable between first and second rotational orientations relative to the valve body to permit right or left hand movement of the handle between the first handle position and the second handle position. 
     The foregoing and other aspects, features, and advantages of the application will become more apparent from the following description and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the application can be better understood with reference to the drawings described below, and the claims. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles described herein. In the drawings, like numerals are used to indicate like parts throughout the various views. 
         FIG.  1    is a drawing showing an exploded view of a new plug type isolation valve according to the Application; 
         FIG.  2 A  is a drawing showing top view of an isolation valve in a left hand configuration, in the closed position; 
         FIG.  2 B  is a drawing showing back view of the isolation valve of  FIG.  2 A ; 
         FIG.  2 C  is a drawing showing another back view of the isolation valve of  FIG.  2 A  with section line AA; 
         FIG.  2 D  is a drawing showing an isometric view of the isolation valve of  FIG.  2 A ; 
         FIG.  2 E  is a cut away drawing of the isolation valve of  FIG.  2 A ; 
         FIG.  2 F  is a cut away drawing of the isolation valve of  FIG.  2 A  along section line AA; 
         FIG.  3 A  is a drawing showing top view of an isolation valve in a left hand configuration, in the open position; 
         FIG.  3 B  is a drawing showing back view of the isolation valve of  FIG.  3 A ; 
         FIG.  3 C  is a drawing showing another back view of the isolation valve of  FIG.  3 A  with section line BB; 
         FIG.  3 D  is a drawing showing an isometric view of the isolation valve of  FIG.  3 A ; 
         FIG.  3 E  is a cut away drawing of the isolation valve of  FIG.  3 A ; 
         FIG.  3 F  is a cut away drawing of the isolation valve of  FIG.  3 A  along section line BB; 
         FIG.  4 A  is a drawing showing top view of an isolation valve in a right hand configuration, in the closed position; 
         FIG.  4 B  is a drawing showing front view of the isolation valve of  FIG.  4 A ; 
         FIG.  4 C  is a drawing showing another front view of the isolation valve of  FIG.  4 A  with section line CC.; 
         FIG.  4 D  is a drawing showing an isometric view of the isolation valve of  FIG.  4 A ; 
         FIG.  4 E  is a cut away drawing of the isolation valve of  FIG.  4 A ; 
         FIG.  4 F  is a cut away drawing of the isolation valve of  FIG.  4 A  along section line CC; 
         FIG.  5 A  is a drawing showing top view of an isolation valve in a right hand configuration, in the open position; 
         FIG.  5 B  is a drawing showing front view of the isolation valve of  FIG.  5 A ; 
         FIG.  5 C  is a drawing showing another front view of the isolation valve of  FIG.  5 A  with section line DD; 
         FIG.  5 D  is a drawing showing an isometric view of the isolation valve of  FIG.  5 A ; 
         FIG.  5 E  is a cut away drawing of the isolation valve of  FIG.  5 A ; 
         FIG.  5 F  is a cut away drawing of the isolation valve of  FIG.  5 A  along section line DD; 
         FIG.  6 A  is a drawing illustrating how a right hand TWH isolation valve can be transitioned to a left hand TWH isolation valve; 
         FIG.  6 B  is a drawing showing the transitioned right hand TWH isolation valve of  FIG.  6 A  as a left hand TWH isolation valve; 
         FIG.  7    is a drawing showing an exploded view of a tankless water heater isolation valve assembly; 
         FIG.  8    is a drawing showing exemplary right and left plates; 
         FIG.  9    is a drawing showing an exploded view of a tankless water heater isolation valve assembly with a hydraulic isolation feature; 
         FIG.  10    is a drawing showing exemplary right and left plates with a notch for the hydraulic isolation feature of  FIG.  9   ; 
         FIG.  11 A  is a drawing showing the first two exemplary steps to set hydraulic isolation; 
         FIG.  11 B  is a drawing showing the last three exemplary steps to set hydraulic isolation; 
         FIG.  12    is a drawing showing an exemplary hot water heaters sharing a common hot water main; 
         FIG.  13    is a drawing showing an exemplary pair of a hot water tankless water heater isolation valve assembly; and 
         FIG.  14    is a block diagram showing how any of the embodiments of the TWH isolation valves described hereinabove can be used with a TWH in a building TWH system; and 
     
    
    
     DETAILED DESCRIPTION 
     As described hereinabove, tankless water heaters heat a cold water flowed into the tankless water heater inlet and provide an on demand heated water from the tankless water heater outlet. One common tankless water heater preventive maintenance is to flow a mild acid such as a food grade vinegar through the internal pipes and heat exchanger to prevent buildup of deposits that could degraded efficiency of the tankless water heater, or even cause a system failure. However, it is important to not introduce the cleaning solution into the water system, typically a potable water system including home hot water systems. Therefore, isolation valve assemblies are provided which allow for the tankless water heater inlet and outlets to be isolated from the cold water feed and hot water supply lines during cleaning operations. 
     One problem with existing isolation valves for tankless water heaters is that a right hand or left hand physical configuration is fixed at time of manufacture. Such fixed structures mean either plumbing for a given right hand or left hand structure or buying particular isolation valves with a needed right hand or left hand physical configuration of ports and valves. 
     Therefore, there is a need for reconfigurable, swappable, or reversible isolation valves for tankless water heaters. 
     Also, as part of the solutions, a relatively compact isolation valve for tankless water heaters was realized, in part, by introduction of a plug type valve. With the symmetry achieved by the plug type valve, it was realized that opposing ports (e.g. threaded ports) can be introduced on either side of a new type of compact isolation valve for tankless water heaters. Either side port can be used for the purge valve/purge port part, the different opposing port either capped by a threaded plug, or available as an option port, such as for an optional sensor, such as a temperature sensor. 
       FIG.  1    is a drawing showing an exploded view of a new plug type isolation valve according to the Application.  FIG.  1    shows an exemplary isolation valve  100  typically used with tankless water heaters. Isolation valve  100  is shown configured with a pressure relief valve  141  for the hot water side of a tankless water heater. A same new type cold water isolation valve according to the Application (not shown in  FIG.  1   ) can omit the pressure relief valve, and can also entirely omit the high pressure relief port. Continuing with  FIG.  1   , a hot water side isolation valve  100  includes four ports in one valve body. Port  193  is adapted to fluidly couple (typically by an intervening pipe) to the hot water outlet of the tankless water heater. Water distribution system port  198  is adapted to fluidly couple to a pipe of a hot water distribution system of a home or building. Port  196  is fluidly coupled to a drain assembly  121  which includes a second on/off valve  125  controlled by handle  123 . Port  195  fluidly couples to the pressure relief valve  141  for the hot water isolation valve type. 
     In normal operation, isolation valve handle  103  is set so that hot water flows normally out of a tankless water heater through the isolation valve  100  and into the home or building hot water distribution system. In a drain operation, typically for testing or cleaning the tankless water heater, isolation valve handle  103  is turned 90° from the normal operation position to the drain position. In a drain operation, port  198  to the hot water distribution system of the home or building is closed. 
     Because of the new use of a plug valve, one aspect of what is new is that there is always water fluidly coupled to port  196 , the fluid connection to the drain assembly  121 , in both the normal operation and in the drain operation. One advantage of this new approach is that the drain assembly, with its own on/off valve  125 , can also be used for diagnostic testing during normal water heater operation without inconveniencing hot water users in the home or building. Another advantage is that plug valve assembly  102  is relatively simple compared to more complex valves which open the normal hot water path, while closing the fluid path to the drain port. A plug valve can also be less complicated and less costly to manufacture than a ball valve of the prior art, at least in part, because the relatively large machined metallic ball is no longer required. 
     Another feature of the new isolation valve is that is reversible for convenient installation, where instead of some specific pipe paths appropriate to a right hand configuration or a left hand configuration, either of a left side port  196 , or a right side port  197  can accept the drain assembly  121 , while a plug  165  can be installed in the non-used side.  FIG.  1    shows a right hand configuration, where in a typical installation below a tankless water heater, isolation valve handle  103  will be on the right side, with the drain assembly pointed outward from the tankless water heater installation (typically outward from a wall on which the tankless water is mounted) (See  FIG.  5 D ). 
     Another feature of the new reversible plug valve based isolation valve  100 , is that during a drain operation, the unused port (port  196  or port  197 ) can be used to accept an option sensor, such as, for example an option temperature sensor or pressure sensor. The extra port of the isolation valve  100  is particularly useful for factory testing, such as factory R&amp;D work, and post production testing operations. However, there can also be diagnostic sensor uses during a drain operation for a tankless water heater installed in the field. While the unused port (port  196  or port  197 ) is blocked during normal operation, the unused port can still be used for a temperature sensor which does not extend all the way into the path of the rotating plug seal of the plug valve. The shallow mount temperature sensor can be used to measure the temperature of the unitary metallic isolation valve body  190  (typically brass, however any suitable metallic material can be used) of the isolation valve  100  during normal operation, a temperature, accounting for radiative loss to the ambient equipment room or basement temperature, indicative of the hot water temperature and hot water flow rate. An isolation valve body  190  can also be manufactured of any suitable non-metallic body as well, however then, the temperature sensor would only be most useful when directly exposed to the fluid flow when the plug is blocking port  198  and the unused port ( 196  or  197 ) is fluidly coupled to the fluid flow. 
     An additional feature of the new reversible plug valve based isolation valve  100 , is that the ports  195 ,  196 ,  197  are located on a single plane. In other words, the flow paths through the ports  195 ,  196 ,  197  intersect. Placing the ports  195 ,  196 ,  197  on a single plane allows the valve  100  to have a shorter height and more easily fit within a compact space when installed on a tankless water heater. In the exemplary embodiment shown, the drain ports  196 ,  197  are each located ninety degrees from the pressure relief port  195 . In other words the flow paths through the ports  196 ,  197  are perpendicular to the flow path through the port  195 . 
     Continuing with  FIG.  1   , the new isolation valve  100  of the Application is described in detail beginning with a table of components for convenient reference. 
     TABLE OR REFERENCE DESIGNATORS FOR FIG.  1   
     
         
         
           
               100  ISOLATION VALVE 
               101  isolation valve plug 
               102  plug valve ASSEMBLY 
               103  isolation valve handle 
               104  plug seal 
               105  isolation valve handle mounting screw 
               107  plug valve stem 
               109  reversible handle stop 
               111   a  right side normal operation stop post 
               111   b  left side normal operation stop post 
               113  plug end seal 
               115  spring clip 
               117  spring slot 
               121  drain ASSEMBLY 
               123  drain valve handle 
               125  drain valve 
               127  drain cap 
               131  tankless water heater connection ASSEMBLY 
               133  compression nut 
               135  compression insert 
               137  compression port seal 
               141  pressure relief valve ASSEMBLY 
               163  unused port seal (sensor port) 
               165  unused port plug 
               190  isolation valve body 
               191  plug valve port 
               193  tankless water heater port (hot water,  FIG.  1   ) 
               195  pressure relief port 
               196  right hand isolation reversible port 
               197  left hand isolation reversible port 
               198  water distribution system port (hot water,  FIG.  1   ) 
           
         
       
    
     Plug valve—Plug valve assembly  102  makes possible the feature of the isolation valve  100  where the drain assembly is always available for use during both normal and drain operations. As shown in  FIG.  1   , in normal operation, plug valve assembly  102  as controlled by isolation valve handle  103  positions plug seal  104  over the unused port, thus opening a normal operation flow path between the tankless water heater (port  193 ) and the hot water distribution system port (port  198 ), thus providing a normal flow of hot water from tankless water heater to the home or building. 
     In a drain operation, in the right hand configuration of  FIG.  1   , isolation valve handle  103  is rotated 90° towards the direction of the drain assembly (typically away from the wall, pointing into the room space, handle about parallel to the long axis of the drain assembly). Now, the plug seal rotates to cover and close the hot water distribution system port  198 . 
     The drain assembly  121  is always conveniently coupled to the tankless water heater, where the drain assembly  121  includes its own on/off drain valve  125 . Thus, particularly during factory R&amp;D or post production testing, there can be diagnostic equipment fluidly coupled to a normally operating tankless water heater by opening drain valve  125  during normal operation (or, during a drain operation). 
     The reversible nature of isolation valve  100  is set to a right hand configuration or a left hand configuration by interchanging (reversing or swapping) the drain assembly  121  and the unused port plug between port  196  and port  197 . The plug valve assembly  102  is always present in port  191 . However, for the handle to turn outward towards the direction of the of the drain assembly  121 , reversible handle stop  109  can be flipped over 180° and reinstalled under isolation valve handle  103  so as to stop either against the right side normal operation stop post  111   a , or the left side normal operation stop post  111   b.    
     Isolation valve plug  101  provides the plug valve frame for rotating plug seal  104  which rotates 90° with rotation of the isolation valve handle. Plug end seal  113  can be any suitable plug valve end seal, typically an O-ring seal as shown in  FIG.  1   . 
     The plug valve assembly can be mounted in to the isolation valve body  190  by any suitable mounting means, such as, for example, by threaded nut, or by spring clip  115  and spring slots  117  as shown in  FIG.  1   . A retaining ring is another suitable method of assembling a plug valve (rotor) into the isolation valve body. 
     The drain assembly  121  includes an on/off drain valve  125  which is controlled by drain valve handle  123 . Drain cap  127  can be a dust cover, such as, for example a plastic dust cap to keep the drain end clear of foreign debris and protect any machine threads. Or, drain cap  127  can be a threaded metal cap with an additional sealing washer or ring to provide a second level of drain closure in addition to drain valve  125 . Drain assembly  121  can be installed in either of port  196  or port  197 , typically by any suitable connection, such as, for example, a threaded mechanical connection. For example, drain assembly  121  can include outer male threads and ports  196 ,  197 , corresponding female machine threads. Any suitable mechanical coupling can be used. Typically, the drain assembly  121  is removable so that the drain assembly can be reversed between either of ports  196 ,  197 , however, especially because such isolation valves are typically only installed once, and are typically not reused, or re-configured during the normal lifetime of the isolation valve, the drain assembly  121  can be supplied uninstalled with a one time non-removable mechanical coupling means to either of ports  196 ,  197 , such as by a one-time mechanical mechanism (e.g. a onetime captive snap lock), and/or adhesive or glue connection. More typically, ports  196 ,  197  are threaded ports which may or may not include an additional threaded sealing compound (e.g. a threaded sealing compound suitable for use with potable water). Most commonly, the drain assembly  121  and unused port plug  165  can be reversed in the field, both at the time of installation, and later if a system is re-configured, or in the less likely event that the isolation valve is re-used for another installation. 
     Tankless water heater port  131  can be fluidly coupled to the tankless water heater by any suitable means. For example, compression nut  133 , compression insert  135 , and compression port seal  137  of  FIG.  1    can be used to fluidly couple the isolation valve  100  to a tankless water heater hot water outlet via a relatively short length of pipe. Any suitable connection can be used, including, for example a flange mount to a tankless water heater. 
     An isolation valve  100  can be provided as an individual isolation valve part. More typically isolation valves are sold in pairs, one for the tankless water heater hot water outlet (e.g.  FIG.  1   ) and one for the cold water side without the high pressure relief valve, where the high pressure relief valve is typically only required on the hot water side. Or, such isolation valves  100  can be supplied with, or supplied already mounted to and fluidly coupled to the hot water outlet and cold water inlet of a tankless water heater. 
       FIG.  2 A  through  FIG.  5 F  show various views of an exemplary hot water side isolation valve  100  in left hand and right hand configurations, in both a normal operation open position and a drain operation closed position. Here, open refers to the normal open path from the hot water outlet of the tankless water heater to the building hot water distribution system, and closed refers to the drain operation, where the normal open path from the hot water outlet of the tankless water heater to the building hot water distribution system is closed (shut off). The convention of left hand and right hand labels are used assuming the isolation valves are commonly installed underneath the tankless water heater. However, there is no such mounting requirement, and those skilled in the art will recognize that there may be applications where a right side installation is defined by the isolation valve handle mounted on the right side as one faces the tankless water heater typically mounted on a wall, or in other less common mounting applications, the isolation valve handle may be up, down, or left in a “right hand” isolation valve configuration. In other words is only important that the drain valve is reversable between ports  196 ,  197 , and that the isolation valve handle  103  can be installed for any convenient 90° rotation by choice of installation size and rotatable position of rotatable handle stop  109  within the isolation valve handle  103  and with respect to the right side normal operation stop post  111   a , or the left side normal operation stop post  111   b.    
     Now, using the convention of the isolation valve mounted in the most common manner underneath a tankless water heater mounted to a wall, 
       FIG.  2 A  is a drawing showing top view of an isolation valve  100  in a left hand configuration, in the closed position.  FIG.  2 B  is a drawing showing back view of the isolation valve of  FIG.  2 A .  FIG.  2 C  is a drawing showing another back view of the isolation valve of  FIG.  2 A  with section line AA.  FIG.  2 D  is a drawing showing an isometric view of the isolation valve of  FIG.  2 A .  FIG.  2 E  is a cut away drawing of the isolation valve of  FIG.  2 A .  FIG.  2 F  is a cut away drawing of the isolation valve of  FIG.  2 A  along section line AA. 
       FIG.  3 A  is a drawing showing top view of an isolation valve  100  in a left hand configuration, in the open position.  FIG.  3 B  is a drawing showing back view of the isolation valve of  FIG.  3 A .  FIG.  3 C  is a drawing showing another back view of the isolation valve of  FIG.  3 A  with section line BB.  FIG.  3 D  is a drawing showing an isometric view of the isolation valve of  FIG.  3 A .  FIG.  3 E  is a cut away drawing of the isolation valve of  FIG.  3 A .  FIG.  3 F  is a cut away drawing of the isolation valve of  FIG.  3 A  along section line BB. 
       FIG.  4 A  is a drawing showing top view of an isolation valve  100  in a right hand configuration, in the closed position.  FIG.  4 B  is a drawing showing front view of the isolation valve of  FIG.  4 A .  FIG.  4 C  is a drawing showing another front view of the isolation valve of  FIG.  4 A  with section line CC.  FIG.  4 D  is a drawing showing an isometric view of the isolation valve of  FIG.  4 A .  FIG.  4 E  is a cut away drawing of the isolation valve of  FIG.  4 A .  FIG.  4 F  is a cut away drawing of the isolation valve of  FIG.  4 A  along section line CC. 
       FIG.  5 A  is a drawing showing top view of an isolation valve  100  in a right hand configuration, in the open position.  FIG.  5 B  is a drawing showing front view of the isolation valve of  FIG.  5 A .  FIG.  5 C  is a drawing showing another front view of the isolation valve of  FIG.  5 A  with section line DD.  FIG.  5 D  is a drawing showing an isometric view of the isolation valve of  FIG.  5 A .  FIG.  5 E  is a cut away drawing of the isolation valve of  FIG.  5 A .  FIG.  5 F  is a cut away drawing of the isolation valve of  FIG.  5 A  along section line DD. 
     Isolation valves according to the Application can use threaded connections. Any suitable threaded, compression, or soldered connections can be used. 
     Swappable Isolation Valve—  FIG.  6 A  is a drawing illustrating how a right hand TWH isolation valve can be transitioned to a left hand TWH isolation valve; 
       FIG.  6 A  and  FIG.  6 B  are drawings that illustrate how a right hand TWH isolation valve can be transitioned to a left hand TWH isolation valve.  FIG.  6 B  is a drawing showing the transitioned right hand TWH isolation valve of  FIG.  6 A  as a left hand TWH isolation valve. A swappable, or reversible isolation valve is shown as a right hand TWH hot water isolation valve  710 , transitioned or re-configured as shown by arrow  799  to a left hand TWH hot water isolation valve  720 . Similarly, the left hand TWH hot water isolation valve  720  can also be transitioned to a right hand TWH hot water isolation valve  710  by reversing the swappable process. 
     As shown in  FIG.  6 A  and  FIG.  6 B , the swappable process (lower left) includes removing the drain assembly  121  from port  196 , removing the unused port plug  165  from port  197 , and removing the handle  103  by removing the screw  105  to remove the reversible handle stop  109 . The reversible handle stop  109  is then flipped over or rotated and/or and then reinstalled between handle  103  and the isolation valve body  190 . Finally, the drain assembly  121  is installed into port  197 , and the port plug  165  is installed into port  196 . 
     Typically, a TWH isolation valve can be configured at time of manufacture, at time of manufacture of the TWH were installed into a TWH product, and/or in the field when an installer installs the isolation valve, typically, but not necessarily, underneath a TWH. 
     A sensor or fluid connection to a diagnostic instrument (not shown in  FIG.  1   ,  FIG.  7   ) can be optionally installed into port  196  in the left hand configuration (right side of  FIG.  1   ,  FIG.  7   ), or into port  197  in the right hand configuration (left side of  FIG.  1   ,  FIG.  7   ). 
     In summary, and generally, with reference to  FIG.  1   , A tankless water heater (TWH) isolation valve  100  includes a valve body  190  having a plug valve port  191 , a TWH port  193 , a water distribution system port  198  and a drain port ( 196 ,  FIG.  1  or  197   ). A plug valve  101  includes at least one plug seal  104 . The plug valve  101  is controlled by a rotatable plug valve handle  103 . The plug valve  101  is disposed through the plug valve port  191  and within the valve body  190 . The rotatable plug valve handle  103  includes a first plug valve handle position and a different rotated second plug valve handle position. In a normal operating mode in the first plug valve handle position ( FIG.  5 A  to  FIG.  5 D ), the TWH port  193  is fluidly coupled to both of the drain port ( 196 ,  FIG.  1  or  197   ) and the water system distribution port  198 . In a drain mode ( FIG.  4 A  to  FIG.  4 D ), the TWH port is fluidly coupled to the drain port ( 196 ,  FIG.  1  or  197   ), and the water system distribution port  198  is closed to the TWH port  193  as blocked by the plug seal  104 . 
     Also, generally, with reference to  FIG.  1   , a tankless water heater (TWH) isolation valve  100  includes a valve body  190  having a plug valve port  191 , a TWH port  193 , a water distribution system port  198 , a first reversible port  196 , and a second reversible port  197 . The first reversible port  196  is disposed about opposite to the second reversible port  197 . A plug valve  101  includes at least one plug seal  104 . The plug valve  101  is controlled by a rotatable plug valve handle  103 . The plug valve  101  is disposed through the plug valve port  191  and within the valve body  190 . A drain valve  121  is mechanically coupled to either of the first reversible port  196  ( FIG.  6 A , left side, right hand isolation valve configuration) or the second reversible port  197  ( FIG.  6 B , right side, left hand isolation valve configuration), and a device (e.g. unused port plug  165 ) is mechanically coupled a different one of the first reversible port  196  or the second reversible port  197 . The rotatable plug valve handle  103  has a first plug valve handle position and a different rotated second plug valve handle position. In a normal operating mode in the first plug valve handle position, the TWH port  193  is fluidly coupled to both of the drain valve  121  and the water system distribution port  198 . In a drain mode, the TWH port  193  is fluidly coupled to the drain valve  121 , and the water system distribution port  198  is closed to the TWH port as blocked by the plug seal  104 . 
     Yet another tankless water heater isolation valve assembly according to the Application is shown in  FIG.  7    and  FIG.  13   . 
       FIG.  7    is a drawing showing an exploded view of a tankless water heater isolation valve assembly  1000 . In this exemplary embodiment, the drain ports (isolation reversible port  196 , and isolation reversible port  197 ) are now offset from the shut-off plug valve (e.g. raised above in  FIG.  7   ). and the pressure relief port  195 . In other words, the ports  196 ,  197  are located on a separate plane from the port  195 . The drain ports are therefore unaffected by plug valve and are always in fluid contact with tankless water heater. One benefit of the arrangement of  FIG.  7   , is that the extra drain port can receive a sensor which is always in contact with the water. Any suitable sensor, including those described hereinabove can be used. Typically, the sensor will be a temperature sensor or a pressure sensor. 
     In  FIG.  7   , both of the isolation reversible port  196  and isolation reversible port  197  are now raised above the isolation valve plug  101  and the plug valve assembly  102 . The isolation reversible port  196 , and isolation reversible port  197  are now part of an isolation reversible port assembly  1010 . Shown for reference in  FIG.  7    are center lines  1051 ,  1061 , and  1071 . The Isolation reversible port assembly  1010  can be seen to be aligned with center line  1061 , offset (e.g. above in  FIG.  7   ) and perpendicular to centerline  1051  of the plug valve assembly  102 . 
       FIG.  8    is a drawing showing exemplary right and left plates. In  FIG.  7   , tab  1011  stops the rotation of stop plate  1009 , and in turn handle  103 . Stop plate  1009  includes a handle direction orientation mark  1705 , side designation text  1701 , and plate stop ledge  1703 .  FIG.  8    is a drawing showing exemplary right and left plates Exemplary retainer ring  1119  (spring clip) snaps into trough  1117  to hold the plug valve assembly  102  together. Exemplary fastener  1005  affixes handle  103  to the isolation valve plug  101 . 
     Isolation reversible port assembly  1010  is still physically part of the tankless water heater isolation valve assembly  1000 , however the fluid flow through the isolation reversible port  196  and the isolation reversible port  197  is no longer controlled by the rotational position of the plug valve assembly  102 . 
       FIG.  13    is a drawing showing an exemplary pair of a hot water tankless water heater isolation valve assembly  1000  and a cold water tankless water heater isolation valve assembly  1101 . Note that the cold water tankless water heater isolation valve assembly  1101  does not need the pressure relief port  195 . The exemplary cold water tankless water heater isolation valve assembly  1101  can optionally excludes isolation reversible port  197 , or the isolation reversible port  197  can be present to allow for reversibility. 
     In summary, and with respect to exemplary  FIG.  7   , a tankless water heater (TWH) isolation valve  100  includes a valve body having a plug valve port  191 , a TWH port  193 , a water distribution system port  198 . A plug valve  101  includes at least one plug seal  104 . The plug valve  101  is controlled by a rotatable plug valve handle  103 . The plug valve  101  is disposed through the plug valve port  191  and within the isolation valve body  190 . A drain port assembly  1010  includes at least one drain port  196 , the at least one drain port  196  an integral part of the isolation valve body  190 . The drain port assembly  1010  is disposed between the TWH port  193  and the plug valve  101 . The drain port assembly  1010  (center line longitudinal axis  1061 ) is offset from the plug valve  101  (center line longitudinal axis  1051 ). 
       FIG.  14    is a block diagram showing how any of the embodiments of the TWH isolation valves described hereinabove can be used with a TWH in a building TWH system. 
     The method of changing from a right handed to a left handed configuration can includes the following steps: 
     1) With purge valve facing the operator and handle placed in off position (handle stem pointing towards the operator), pull handle off from the valve, disconnecting from the rotor (rotating plug) 
     2) Swap purge valve position with the brass plug on the opposite side of the valve 
     3) Rotate the whole valve assembly so the purge valve is again facing the operator 
     4) Remove Handle stop marked as “RIGHT HAND” and replace with additionally provided handle stop marked as “LEFT HAND” 
     5) Reattach handle to the rotor (rotor still in off position), with the handle stem pointing towards the operator and in the same direction as the purge valve 
     6) When complete, handle should now be on the left side, with operator facing purge valve, and handle stem pointing at the operator. Sealing portion of the rotor should be over the residential connection port for the hot side valve. 
     7) Handle will now only rotate from pointing towards the operator to 90 degrees downward pointing towards direction of the flow (away from TWH on the hot side). 
     Hydraulic Isolation feature—When used in modular installations, such as where a plurality of hot water heaters share a common hot water main, a valve assembly according to the Application which further includes a hydraulic isolation feature can be field configured to provide hydraulic isolation of units that need service or repair while other units remain operating.  FIG.  12    is a drawing showing an exemplary hot water heaters sharing a common hot water main. 
       FIG.  9    is a drawing showing an exploded view of a yet another tankless water heater isolation valve assembly with a hydraulic isolation feature.  FIG.  10    is a drawing showing exemplary right and left plates with a notch for the hydraulic isolation feature of  FIG.  9   . 
     The tankless water heater isolation valve assembly of  FIG.  9    and  FIG.  10    is similar to the tankless water heater isolation valve assembly of  FIG.  7    and  FIG.  8    with the addition of hydraulic isolation position notches in the right and left stop plates. 
     To provide hydraulic isolation from a pressurized hot water main using the valve assembly of  FIG.  9    and  FIG.  10   , the pressure-activated seal can be rotated 180 degrees from the bottom port to the upper port. 
     Generally, the plug valve is rotated into a hydraulic isolation position, and mechanically set to that position by the hydraulic isolation position notch  901  of the stop plate  1009  ( FIG.  9   ,  FIG.  10   ) seating over the tab  1011  ( FIG.  7   ,  FIG.  9   ). 
     As illustrated by the exemplary steps of  FIG.  11 A  and  FIG.  11 B .  FIG.  11 A  is a drawing showing the first two exemplary steps to set hydraulic isolation.  FIG.  11 B  is a drawing showing the last three exemplary steps to set hydraulic isolation. First, A) With the valve in the closed position (handle facing forwards), remove handle plug, handle and stop plate. B) Place handle back on rotor hub and rotate 180 degrees so handle is facing rearward. C) Remove handle and re-install stop plate aligning the notch (marked with a X) with the nub on the body. D) Re-install handle (facing to the rear) and handle plug. The valve will now provide hydraulic isolation from a pressurized hot water main and be locked closed to prevent operation of water heater. Finally, E) To place heater back in commission, reverse the above process. 
     It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.