Abstract:
A fluid pumping system with energy recovery features may be used to provide feed water to a reverse osmosis unit. The system includes an electronic controller unit that regulates the output of three hydraulic pumps. Each hydraulic pump drives the movement of a piston in a cylinder. The pistons collectively deliver a generally constant flow of high pressure feed water to the reverse osmosis unit. Concentrate valve bodies direct concentrate from the reverse osmosis unit to the back sides of the pistons to reduce the work required from the hydraulic pumps. The concentrate valve bodies are designed to open and close based upon the flow of concentrate through the valve bodies. The piston and cylinder are designed for exposure to sea water and RO brine.

Description:
This invention was made with government support under Assistance Agreement No. 1425-5-FC-81-20410 awarded by the U.S. Department of the Interior, Bureau of Reclamation. 
    
    
     FIELD 
     The present disclosure relates generally to a valve system for recovering energy from pressurized fluids. 
     BACKGROUND 
     Many areas of the world do not have adequate fresh water supplies, but they are able to obtain seawater. Seawater can be desalinated using reverse osmosis, among other processes. To desalinate seawater by reverse osmosis (RO), the feed water must be pressurized above the osmotic pressure of the feed water. The feed water becomes concentrated during the process, and its osmotic pressure increases. Typical feed water pressures for seawater reverse osmosis (SWRO) are in the range of 50-70 bar. 
     Given the high feed water pressures, energy costs (typically in the form of electrical consumption) are the largest component of the operating cost of a SWRO plant. Through various improvements, the amount of energy used per unit of water produced by SWRO has decreased over time. For example, high pressure multi-stage turbine pumps have become more efficient, to about 70% nominal efficiency. Power recovery turbines are now used to recover some of the energy in the concentrated brine flow leaving the RO modules. Recovery rates have been optimized to balance the cost of pre-treating and pumping feed water (which decreases with increased recovery rate) with the cost of producing desalinated water (which increases with increased recovery rate). Despite these improvements, however, energy costs are still a significant portion of the cost of desalinated water. 
     Energy consumption also interferes with adopting advances in RO membrane technology. Advances in RO membrane technology have included membrane elements that are capable of operating above 70 bar, and with recovery rates of 55% or more. In theory, a higher recovery rate should allow for decreased capital costs and decreased raw feed water flow. Decreasing the flow of raw feed water would in turn produce savings in pre-treatment and feed water pumping, and reduce the environmental damage caused by withdrawing seawater. However, as mentioned above, when the feed water is concentrated its osmotic pressure increases. As recovery rate increases, so does the feed water concentration, osmotic pressure and energy consumption. The key to breaking this cycle is to recovery more of the energy imbedded in the brine leaving the RO modules. The pressure of the brine also increases with osmotic pressure. Accordingly, there is more energy embedded in the brine of a high recovery process. If a greater percentage of this embedded energy can be recovered, there will be a direct reduction in energy consumption, as well as the possibility of further reductions due to an increase in the optimal recovery rate. 
     Despite incremental improvements over time, turbine based pumps and energy recovery devices are limited in their energy efficiency. Turbine based technologies are used because they are familiar and easy to use to produce constant flow rates and pressures through the SWRO plant. Adopting a different approach, Childs et al. described a piston based pumping and energy recovery system in U.S. Pat. No. 6,017,200, entitled Integrated Pumping and/or Energy Recovery System. This system uses a piston driven by a hydraulic pump to provide pressurized feed water to an RO membrane module. The front face of the piston drives the feed water to the RO module. The back face of the piston receives brine from the RO module. The pressure of the brine acting on the back face of the piston reduces the power required from the hydraulic pump to move the piston. 
     In the Childs et al. system, “energy recovery” valves admit brine to the back face of the piston on a forward stroke. Additional discharge valves allow the admitted brine to leave the piston on a backward stroke. The energy recovery and discharge valves are controlled by a control unit that also operates the hydraulic pump. The control unit synchronizes the movements of the valves with the movement of the piston. Because the piston reciprocates, it must accelerate and decelerate and therefore inherently produces an uneven rate of flow and pressure of the feed water. However, when a set of pistons are used, their output may be synchronized to produce a fluctuating, but nearly constant, combined out pressure. Although subject to various practical difficulties, the Childs et al. system has the potential to efficiently produce a high pressure flow of feed water. 
     SUMMARY OF THE INVENTION 
     The present disclosure describes a valve system to provide a flow of pressurized fluid. The valve system may be used with a pumping system and process, for example, to provide feed water to a reverse osmosis (RO) system and recover energy from the brine leaving the RO system. The system and process have a set of piston based pumps, valves to return brine to the pumps, and an electronic controller for operating the pumps and valves. The system and process are generally similar to the Childs et al. system described above. 
     The energy recovery and discharge valves described in U.S. Pat. No. 6,017,200 were moved between open and closed states by a solenoid that was in turn operated by the control unit. In the apparatus described herein, valves are used which respond to variations in the rate of flow through them. In particular, the valves move towards a closed position when the rate of flow through them decreases. 
     Mechanically, the present valve system has a piston that closes against a downstream seat inside of a valve body. The face of the piston has two effective surface areas, for example a central area and an outer ring. Water flowing through the valve passes around the piston. The outer ring is located upstream of the valve seat which creates a bend in the flow path of the valve body that causes a head loss to flowing water. Because of this head loss, and the displacement of the outer ring upstream of at least part of the head loss, when water is flowing though the valve the static pressure on the central area of the piston is less than the static pressure on the outer ring. The back of the piston is connected to the downstream static pressure. Accordingly, when water is flowing through the valve, the piston is pushed towards an open position by a force that increases with the flow rate of the water. A spring may be used to bias the piston towards the closed position. At high flow rates, the additional pressure on the outer ring, relative to the downstream pressure in the valve body, overcomes the spring and keeps the valve open. However, as the flow rate decreases, the additional pressure on the outer ring decreases and the valve is able to move towards a closed position. A pilot valve is used to selectively connect the back of the piston in fluid communication with either upstream or down stream of the piston. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing of a fluid pumping and energy recovery system in combination with a reverse osmosis system. 
         FIG. 2  is a cross-sectional, schematic view of an energy recovery valve, alternatively called a concentrate valve, used in the system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     As depicted in  FIG. 1 , a system  10  includes a source of feed water  110 , three hydraulic pumps  12 , a water cylinder  200  for each hydraulic pump  12 , an RO membrane unit  216 , and a control unit  100 . The system  10  is similar to the system described in U.S. Pat. No. 6,017,200, which is incorporated by reference, but will also be described below. 
     Under instruction from the control unit  100 , each hydraulic pump  12  controls the movement of an individual piston rod  14 . The piston rod  14  is mechanically coupled to two, dual-action pistons (not shown in  FIG. 1 ), that are housed within a water cylinder  200 . As will be further described below, the hydraulic output of each hydraulic pump  12  causes the piston rod  14  to move. Due to the mechanical coupling, the movement of the piston rod  14  causes the two, dual-action pistons to move in unison with the movement of the piston rod  14 . The piston rod  14  and the two-dual action pistons may collectively be referred to as a reciprocating assembly. For clarity, this disclosure will describe the features of a single pump and reciprocating assembly, but it is understood that this similarly describes the features of all the hydraulic pumps and reciprocating assemblies in the system. 
     A source of feed water  110 , which includes sources of sea water, brackish water and the like, is connected to and supplies feed water to the water cylinder  200  by feed water supply lines  254 ,  256  (indicated as the long dashed line in  FIG. 1 ). 
     The system  10  also includes high pressure feed water supply lines  262 ,  264  to direct a high pressure feed water from the water cylinder  200  to the RO membrane unit  216  (indicated as the thick solid line in  FIG. 1 ). 
     The RO membrane unit  216  produces a volume of permeate, that is desalted water, which is directed by the permeate line  217  for the desired uses of the desalinated filtrate product. The RO membrane unit  216  also produces a volume of high pressure concentrate. The high pressure concentrate is directed from the RO membrane unit  216  by lines  218 ,  219  back to the water cylinder  200  (indicated as the dotted lines in  FIG. 1 ). 
     The water cylinders  200  also include a low pressure concentrate outlet, as described further below, that is connected to low pressure concentrate discharge lines  250 ,  252  which direct the low pressure concentrate to a waste stream or recycle stream depending upon the particulars of the overall system (indicated as the thin solid line in  FIG. 1 ). 
     From a general perspective, there are four distinct hydrostatic pressures within this system. The first pressure P 1  is the pressure that supplies the feed water from the source  110 , through lines  254 ,  256  to the water cylinder  200 . P 1  can be provided by a variety of known pumps. The second pressure P 2 , which is substantially higher than P 1 , is the pressure exerted on the feed water from the water cylinder  200 , through lines  262 ,  264 , to the RO membrane unit  216 . As described below, P 2  is provided by the dual-action pistons  224 ,  226  of the water cylinder  200 . The third pressure P 3 , is the hydrostatic pressure of the concentrate fluid as it leaves the RO membrane unit  216  to return to the water cylinder  200 , via lines  218 ,  219 . P 3  is slightly less than P 2  because some of the energy is used to drive the desalinated water out of the RO membrane unit  216 , into permeate line  217 . The fourth pressure P 4  is the pressure of the concentrate as it leaves the water cylinder  200  via lines  250 ,  252  to the waste or recycling stream. P 4  is less than P 3 . 
     For example, P 1  is substantially in the range of 5 to 100 p.s.i.; P 2  is in the range of 600 to 1000 p.s.i.; P 3  is in the range of 500 to 950 p.s.i.; and P 4  is 1 to 50 p.s.i. 
     As shown in  FIG. 1 , the water cylinder  200  also includes two concentrate valve bodies  400 ,  401 , alternatively called energy recovery valves. The concentrate valve bodies  400 ,  401  are positioned between lines  218 ,  219 , and the concentrate access ports  242 ,  244  (see  FIG. 1 ). The specific features and functions of the concentrate valve bodies  400  and  401  are the same, with the exception of the specific connections between the concentrate working chamber and the high pressure concentrate lines  218 , 219 . Therefore the present disclosure will describe the concentrate valve body  400  and it is understood that this described is inclusive of the concentrate valve body  401 . 
     As shown in  FIG. 2 , the concentrate valve body  400  includes concentrate flow control valves  402 ,  502  to control the flow of concentrate into and out of concentrate access port  242 . The concentrate valve body  400  has a first end  404 , also referred to as the high pressure input end, that is in fluid communication with the high pressure concentrate line  218 . The concentrate valve body  400  also has a second end  406 , also referred to as the low pressure output end, that is in fluid communication with the low pressure discharge line  250 . Between the two ends there is a central chamber  414  that is in fluid communication with the concentrate access port  242 . 
     The concentrate valve body  400 , includes concentrate flow control valves  402 ,  502 . The concentrate control valves  402 ,  502  are also referred to as the inlet valve  402  and the outlet valve  502 . The inlet valve  402  is positioned between the first end  404  and the central chamber  414  of the concentrate valve body  400 . The outlet valve  502  is located between the central chamber  414  and the second end  406 . 
     The inlet valve  402  includes a manifold plate  427 , an inlet valve seat  418  and an inlet valve piston  416 . The manifold plate  427  is positioned between the first end  404  and the central chamber  414 . The manifold plate  427  extends across the inner surface of the concentrate valve body  400  and includes a high pressure port  430  to provide fluid communication between the first end  404  and a high pressure chamber  432 . The high pressure chamber  432  is located between the manifold plate  427  and the inlet valve seat  418 . The inlet valve seat  418  is located between the manifold plate  427  and the central chamber  414 . The inlet valve seat  418  includes a central aperture or a series of apertures so that when the inlet valve piston  416  is displaced from the inlet valve set  418 , as further described below, fluid may flow from the high pressure chamber  432 , past the inlet valve seat  418  into the central chamber  414 . 
     The inlet valve piston  416  is located between the manifold plate  427  and the inlet valve seat  418 . The inlet valve piston  416  has a first surface  419  that faces towards the manifold plate  427 , also referred to as the back of the inlet valve piston. The inlet valve piston also include a second surface  421  that faces towards the inlet valve seat  418 , also referred to as the front of the inlet valve piston. The second surface  421  includes a stepped region  417  that establishes two effective surface areas, a central area  423  and an outer ring  425 . When the second surface  421  is seated in the inlet valve seat  418 , as described further below, the central area  423  is in direct contact with the inlet valve seat  418  and the outer ring  425  is recessed from the inlet valve seat  418 . 
     The manifold plate  427  includes a manifold plate extension  434  that restricts the movement of the inlet valve piston  416  to actuate in a single plane, between an open position and a closed position. The manifold plate extension  434  extends away from the manifold plate  427 , towards the central chamber  414  forming a plenum between the manifold plate  427 , the manifold plate extension  434  and the first surface  419 . The manifold plate extension  434  extends around the inlet valve piston  416 , thereby restricting the movement of the inlet valve piston  416  to move either towards or away from the manifold plate  427  and thereby towards or away from the inlet valve seat  418 . 
     The high pressure chamber  432  is defined by the inner surface of the concentrate valve body  400 , the manifold plate  427 , the manifold plate extension  434  and at least partially by the inlet valve piston  416 , as will be discussed further below. Via the high pressure port  430 , the manifold plate  427  isolates the first surface  419  of the inlet valve piston  416  from the high pressure concentrate fluid flow that enters the concentrate valve body  400  from the first end  404 . 
     Optionally, an inlet spring  429 , for example an extension spring, can be positioned between and in contact with the manifold plate  427  and the first surface  419  of the inlet valve piston  416 . The inlet spring  429  provides a physical biasing force that directs the inlet valve piston  416  towards the inlet valve seat  418 . 
     The inlet valve piston  416  is moveable, within the confines of the manifold plate extension  434 , to position the second surface  421  of the inlet valve piston  416  in direct contact with the inlet seat  418 , this is referred to as the closed position. When the inlet valve  402  is in the closed position, there is no fluid communication between the inlet valve piston  416  and the inlet valve seat  418  and therefore there is no fluid communication between the first end  404  and the central chamber  414 . Further, when the inlet valve piston  416  is in the closed position it contributes to defining the high pressure chamber  432  (as shown in  FIG. 2 ). When the inlet valve piston  416  is in the closed position, the inlet fluid path between the first end  404  and the central chamber  414  terminates in the high pressure chamber  432 . 
     The inlet valve piston  416  is also moveable to position the second surface  421  away from the inlet seat  418 , this is referred to as the open position. When the inlet valve piston  416  is in the open position, the inlet fluid flow path is open between the inlet valve piston  416  and the inlet valve seat  418 . This inlet fluid flow path provides fluid communication from the first end  404  to the central chamber  414  and ultimately into the concentrate working chamber of the water cylinder  200 . When the inlet valve piston  416  is in the open position it contributes only partially to defining the high pressure chamber  432  because the inlet fluid path is open between the inlet valve piston  416  and the inlet valve seat  418 . When the inlet valve piston  416  is in the open position, an inlet fluid path between the first end  404  and the central chamber passes through the high pressure chamber  432 . 
     The inlet valve  402  includes an inlet valve actuator  420  that responds to instructions from the control unit  100 . Instructions from the control unit  100  cause the inlet valve piston  416  to actuate between the open position and the closed position. 
     The inlet valve actuator  420  includes a solenoid  450  that responds to electrical signals from the control unit  100 . Based upon the electrical signals received from the control unit  100 , the solenoid  450  can activate thereby connecting an air compressor  452  to an air line  454 . The air line  454  is connected to one end of a pilot valve body  456 . The solenoid  450  can also de-activate thereby connecting the air line  454  to a vent port (not shown) of the solenoid valve  450 . The pilot valve body  456  includes a pilot valve piston  458 , which has one piston face that faces the pressurized air line  454 . The pilot valve piston  458  also has an opposite piston face that is connected to a pilot valve stem  460 . The pilot valve stem  460  extends away from the pilot valve piston  458 . The pilot valve stem  460  extends away from the pilot valve piston  458  through a pilot valve chamber  462 . The pilot valve stem  460  can move within the pilot valve chamber  462  without creating any pressure or fluid seals therein. 
     Three separate channels branch off of the pilot valve chamber  462 : a first pilot chamber  464 ; a second pilot chamber  466 ; and a third pilot chamber  468 . The first pilot chamber  464  is connected to the first end  404  to provide fluid communication between the first end  404  and the pilot valve chamber  462 . The second pilot chamber  466  is connected between the pilot valve chamber  462  and the first surface  419  of the inlet valve piston  416 . The second pilot chamber  466  can extend through the manifold plate  427  to provide fluid communication between the first surface  419  of the inlet valve piston  416  and the pilot valve chamber  462 . The third pilot chamber  468  is connected between the pilot valve chamber  462  and the central chamber  414 , providing fluid communication therebetween. 
     The pilot valve chamber  462  also includes a pilot ball valve  470 , an inlet pilot ball valve seat  472  and an outlet ball valve seat  474 . The pilot ball valve  470  can move between an inlet position and an outlet position. When the pilot ball valve  470  is seated in the inlet pilot ball valve seat  472 , this is referred to as the inlet position. When the pilot ball valve  470  is seated in the outlet pilot ball valve seat  474 , this is referred to as the outlet position. In  FIG. 2 , the pilot ball valve  470  is shown in the outlet position. 
     When the pilot ball valve  470  is in the inlet position, there is no fluid communication between the first pilot chamber  464  and the second pilot chamber  466 . When the pilot ball valve  470  is in the inlet position there is fluid communication between the second pilot chamber  466  and the third pilot chamber  468 . 
     When the pilot ball valve  470  is in the outlet position, there is fluid communication between the first pilot chamber  464  and the second pilot chamber  466 . When the pilot ball valve  470  is in the outlet position, a fluid path is opened from the first end  404 , through the first pilot chamber  464  the second pilot chamber  466  to the first surface  419  of the inlet valve piston  416 . Pressurized concentrate that follows this fluid path causes the inlet valve piston  416  to move into direct contact with the inlet valve seat  418 , the closed position. 
     The outlet valve  502  is located within the concentrate valve body  400 , between the second end  406  and the central chamber  414 . The outlet valve  502  includes a manifold plate  527 , an outlet valve seat  518  and an outlet valve piston  516 . The manifold plate  527  is positioned between the second end  406  and the central chamber  414 . The manifold plate  527  extends across the inner surface of the concentrate valve body  400  and includes a flow port  530  that provides fluid communication between the central chamber  414  and a pressure chamber  532 . The pressure chamber  532  is located between the manifold plate  527  and the outlet valve seat  518 . The outlet valve seat  518  is located between the manifold plate  527  and the second end  406 . The outlet valve seat  518  is smaller in cross-section than the outlet valve piston  516 . The outlet valve seat  518  includes a central aperture or a series of apertures so that when the outlet valve piston  516  is displaced from the outlet valve set  518 , as further described below, fluid may flow from the high pressure chamber  532 , past the outlet valve seat  518  towards the second end  406 . 
     The outlet valve piston  516  is located between the manifold plate  527  and the outlet valve seat  518 . The outlet valve piston  516  has a first surface  519  that faces towards the manifold plate  527 , also referred to as the back of the outlet valve piston. The outlet valve piston also includes a second surface  521  that faces towards the outlet valve seat  518 , also referred to as the front of the outlet valve piston  516 . When the second surface  521  is seated in the outlet valve seat  518 , as described further below, the central area  523  is in direct contact with the outlet valve seat  518  and the outer ring  525  is recessed from the outlet valve seat  518 . 
     The movement of the outlet valve piston  516  is restricted by a manifold plate extension  534  to actuation in a single plane, between an open position and a closed position. The manifold plate extension  534  extends away from the manifold plate  534 , towards the second end  406  and the manifold plate extension  534  extends around the outlet valve piston  516 . The manifold plate extension  534  forms a plenum between the manifold plate  527  and the first surface  519 . The manifold plate extension  534  restricts the movement of the outlet valve piston  516  to move either towards or away from the manifold plate  527  and thereby towards or away from the outlet valve seat  518 . 
     The pressure chamber  532  is defined by the inner surface of the concentrate valve body  400 , the manifold plate  527 , the manifold plate extension  534  and at least partially by the outlet valve piston  516 , as will be discussed further below. The manifold plate  527  can isolate the first surface  519  of the outlet valve piston  516  from the concentrate fluid flow within the central chamber  414 . 
     Optionally, an outlet spring  529 , for example a cylindrical compression spring, may be placed in contact with the manifold plate  527  and the first surface  521  of the outlet valve piston  516 . The outlet spring  529  provides a physical biasing force that drives the outlet valve piston  516  towards the outlet valve seat  518 . 
     The outlet valve piston  516  is moveable, within the confines of the manifold plate extension  534  to position the second surface  521  of the outlet valve piston  516  in direct contact with the outlet seat  518 , this is referred to as the closed position. When the outlet valve  502  is in the closed position, there is no fluid communication between the outlet valve piston  516  and the outlet valve seat  518 . When the outlet piston  516  is in the closed position there is no fluid communication between the central chamber  414  and the second end  406 . When the outlet valve piston  516  is in the closed position it contributes to defining the pressure chamber  532  (as shown in  FIG. 2 ). Therefore, when the outlet valve piston  516  is in the closed position, an outlet fluid path between the central chamber  414  and the second end  406  terminates in the pressure chamber  532 . 
     The outlet valve piston  516  is moveable to position the second surface  521  away from the outlet seat  518 , this is referred to as the open position. When the outlet valve piston  516  is in the open position, the outlet fluid flow path is established between the outlet valve piston  516  and the outlet valve seat  518 . This outlet fluid flow path provides fluid communication from the central chamber  414  to the second end  406  and ultimately to line  250  for waste or recycling. When the outlet valve piston  516  is in the open position it partially contributes to defining the pressure chamber  532  because the outlet fluid path is now open between the outlet valve piston  516  and the outlet valve seat  518  and the pressure chamber  532  is fluid communication with the second end  406 . Therefore, when the outlet valve piston  516  is in the open position, an outlet fluid path between the central chamber  414  passes through the pressure chamber  532 . 
     The outlet valve  502  includes an outlet valve actuator  520  that responds to instructions from the control unit  100 . Instructions from the control unit  100  cause the outlet valve piston  516  to actuate between the open position and the closed position. 
     The outlet valve actuator  520  includes a solenoid  550  that responds to electrical signals from the control unit  100 . Based upon the electrical signals received from the control unit  100 , the solenoid  550  can activate thereby connecting an air compressor  552  to an air line  554 . The air line  554  is connected to one end of an outlet pilot valve body  556 . The solenoid  550  can also de-activate thereby connecting the air line  554  to a vent port (not shown) of the solenoid valve  550 . The outlet pilot valve body  556  includes an outlet pilot valve piston  558 , which has one piston face that faces the pressurized air line  554 . The pilot valve piston  558  also has an opposite piston face that is connected to an outlet pilot valve stem  560 . The outlet pilot valve stem  560  extends away from the outlet pilot valve piston  558 . The outlet pilot valve stem  560  extends away from the outlet pilot valve piston  558  through an outlet pilot valve chamber  562 . The outlet pilot valve stem  560  can move within the outlet pilot valve chamber  562  without creating any pressure or fluid seals therein. 
     Three separate channels branch off of the outlet pilot valve chamber  562 : a first outlet pilot chamber  568 ; at second outlet pilot chamber  566 ; and a third outlet pilot chamber  564 . 
     The first outlet pilot chamber  568  is connected between the pilot valve chamber  562  and the central chamber  414 , providing fluid communication therebetween. The second outlet pilot chamber  566  is connected between and the first surface  519  of the outlet valve piston  516 . The second outlet pilot chamber  566  can extend through the manifold plate  527 . The second outlet pilot chamber  566  establishes fluid communication between the first surface  519  of the outlet valve piston  516  and the outlet pilot valve chamber  562 . The third outlet pilot chamber  564  is connected between the second end  406  and the outlet pilot valve chamber  562  to establish fluid communication therebetween. 
     The pilot valve chamber  562  also includes an outlet pilot ball valve  570 , an inlet pilot ball valve seat  572  and an outlet ball valve seat  574 . The outlet pilot ball valve  570  can be seated in the inlet pilot ball valve seat  572 , referred to as the inlet position. The outlet pilot ball valve  570  can also be seated in the outlet pilot ball valve seat  574 , referred to as the outlet position. 
     When the outlet pilot ball valve  570  is in the inlet position, there is fluid communication between the central chamber  414  and the first surface  519  of the outlet valve piston  516 . When the outlet pilot ball valve  570  is in the inlet position, there is no fluid communication between the second pilot chamber  566  and the third outlet pilot chamber  564  and the outlet valve piston  516  is in the closed position. 
     When the outlet pilot ball valve  570  is in the outlet position, there is no fluid communication between the central chamber  414  and either of the second outlet pilot chamber  566  or the third outlet pilot chamber  564 . When the outlet pilot ball valve  570  is in the outlet position fluid communication is established between the second outlet pilot chamber  566  and the third outlet pilot chamber  564 . When the outlet pilot ball valve  570  is in the outlet position, the outlet valve piston  516  is in the open position. When the outlet valve piston  516  is in the open position an outlet fluid passage is provided from the central chamber  414  to the second end  406  through the discharge flow port  530  and the pressure chamber  532 . 
     In an additional optional feature of the concentrate valve body  400 , the pressure chamber  532  includes a pressure relief system  600 . The pressure relief system  600  includes an outlet pressure relief valve  602  and an outlet pressure relief chamber  604 . The outlet pressure relief valve  602  is positioned between the pressure chamber  532  and the second end  406 , as shown in  FIG. 2 . The outlet pressure relief chamber  604  provides fluid communication between the pressure chamber  532  and the second end  406 . The outlet pressure relief valve  602  can be any type of known pressure relief valve that will actuate when the pressure within the pressure chamber  532  increases beyond a set point, for example 500 to 1000 p.s.i. Actuation of the outlet pressure relief valve  602  will allow fluid communication from the pressure chamber  532  to the second end  406 . 
     In an additional optional feature, the pilot valve bodies  456 ,  556  includes a spring (not shown) that provides a biasing force to physically direct the pilot valve pistons  458 ,  558  away from the pilot ball valves  470 ,  570 . The pilot valve stems  460 ,  560  will similarly move away from the pilot ball valves under this biasing force. The biasing force of this spring is lower than the air pressure delivered by the lines  454 ,  554 , for example 100 p.s.i. so that this spring will only physically move the pilot valve pistons  458 ,  558  when there is no air pressure delivered to the piston face. 
     High pressure concentrate may periodically enter the valve body  400  via the inlet  404 , this is referred to as the inlet phase. The high pressure concentrate enters the valve body  427  and flows around the manifold plate  427  and enters the high pressure chamber  432 . At the onset of the inlet phase, the inlet valve piston  416  is in the closed position and the pilot ball valve  470  is in the outlet position. The flow of high pressure concentrate into the high pressure chamber  432  acts on the outer ring  425  of the inlet valve piston  416 . The hydrostatic pressure in the central chamber  414  and the second pilot chamber  466  will equalize due to the movement of the pilot ball valve  470  to the inlet position. Therefore the hydrostatic pressure acting on the first surface  419  of the inlet valve piston  416  is the same as the hydrostatic pressure within the central chamber  414 . At the beginning of the inlet phase, the hydrostatic pressure within the central chamber  414  is lower than the hydrostatic pressure of the high pressure concentrate within the high pressure chamber  432 . Therefore, the hydrostatic pressure acting upon the outer ring  425  is greater than the pressure acting on the first surface  419  of the inlet valve piston  416 . This pressure differential causes the inlet piston valve  416  to move to the open position. 
     As the high pressure concentrate flows through the area of inlet valve seat  418 , turbulence can occur and cause head loss. Due to this head loss, even when the inlet valve piston  416  is in the open position, the hydrostatic pressure within the central chamber  414  is less than the hydrostatic pressure within the high pressure chamber  432 . The outer ring  425  is positioned upstream of at least a portion of the head loss, due to being recessed from the central area  423 . Therefore, the pressure acting upon the outer ring  425  remains greater than the pressure within the central chamber  414 . Further, the hydrostatic pressure acting upon the outer ring is greater than the physical biasing force of the inlet spring  429 . The flow of high pressure concentrate from the high pressure chamber  432  into the central chamber  414  allows the inlet valve piston  416  to remain in the open position. 
     During the inlet phase the control unit  100  sends electrical signals to the electronically controlled actuators  420 ,  520  of the concentrate valve bodies  400 ,  401 . As described above, both of the inlet actuator  420  and the outlet actuator  520  are responsive to electrical signals, for example a change in voltage, current and the like, from the electronic controller unit  100 . In response to instructions from the control unit  100 , the concentrate valve body  400  actuates, for example the position of the pilot ball valve  470  and the outlet pilot ball valve  570  can change from the outlet position to the inlet position. 
     During the inlet phase the control unit  100  sends electric signals to the inlet valve actuator  420 . The inlet valve actuator  420  actuates the solenoid  450  to cause the inlet air compressor  452  to act on the pilot valve piston  458 . The air pressure on the pilot valve piston  458  causes the pilot valve stem  460  to direct the pilot ball valve  470  into the inlet position. 
     The hydrostatic force of the high pressure concentrate within the second pilot chamber  466  and the physical biasing force of the inlet spring  429  both act upon the first surface  419  of the inlet valve piston  416 . When the pilot ball valve  470  is in the inlet position, the second pilot chamber  466  is in fluid communication with the pilot valve chamber  466  and the third pilot chamber  468 . This fluid communication allows any concentrate fluids within the second pilot chamber  466  to flow into the central chamber  414 . 
     The movement of the pilot ball valve  470  equilibrates the hydrostatic forces acting on the first surface  419  with the static pressure within the central chamber  414 . 
     During the inlet phase, the outlet valve piston  516  is in the closed position which directs the high pressure concentrate entering the central chamber  414  to enter the concentrate access port  242 . 
     During the inlet phase, the high pressure concentrate will flow through the central chamber  414  to enter the first outlet pilot chamber  568  and the outlet pilot valve chamber  542  and direct the outlet ball valve  570  to sit in the inlet pilot ball valve seat  572 , the inlet position. During the inlet phase, the control unit  100  decreases the pressure acting upon the outlet pilot valve piston  558 . Therefore, the outlet pilot valve stem  560  does not act upon the outlet pilot ball valve  570 , against the high pressure concentrate within the outlet pilot valve chamber  542 . 
     When the outlet ball valve  570  is in the inlet position, there is fluid communication between the third pilot chamber  568  and the second outlet pilot chamber  566  so that the high pressure concentrate flows from the central chamber  414  into the second outlet pilot chamber  566  to act upon the first surface  519  of the outlet valve piston  516 . During the inlet phase, the high pressure concentrate also flows around the manifold plate  527 , through the flow port  530  and into the pressure chamber  532 . The combined pressure of the high pressure concentrate on the first surface  519  and the outlet spring  529  is greater than the force of the high pressure concentrated upon the outer ring  525  and the outlet valve piston  516  is in the closed position. As described above, if the outlet valve piston  516  is in the closed position, then there is no fluid communication provided between the pressure chamber  532  and the outlet end of the concentrate valve body  400 . 
     Periodically, the valve body  400  can experience an outlet phase. During the outlet phase there is little to no flow of high pressure concentrate entering the valve body  400  at the inlet  404 . Further, there is a flow of fluid from the port  242  into the central chamber  414 . The little or no flow of high pressure concentrate within the high pressure chamber  432  allows the inlet valve piston  416  to move to the closed position. 
     During the outlet phase, the outlet valve piston  516  can open in a manner similar to the inlet valve piston  416  during the inlet phase. The flow of concentrate from the central chamber into the pressure chamber  532  will act upon the outer ring of the outlet valve piston  516 . This flow of concentrate has a higher hydrostatic pressure than the pressure within the outlet at the second end  406  and the hydrostatic pressure action upon the first surface  519 . Therefore, the outlet valve piston  516  moves to the open position. Similarly, the flow of concentrate through the area of the outlet valve seat  518  will experience a head loss. The positioning of the outer ring  525  upstream of at least a substantial portion of the head loss allows the outlet valve piston to remain open during constant flow of concentrate from the central chamber  414  to the outlet at the second end  406 . 
     During the outlet phase, the control unit  100  can send electric signals to allow the discharge or outlet of the concentrate from the central chamber  414 . 
     Under instruction from the control unit  100 , the air compressor  452  does not provide any air pressure through line  454  to act upon the inlet pilot valve piston  458  and the pilot ball valve  470  is directed to the outlet position. When the pilot ball valve  470  is in the outlet position, there is fluid communication between the first pilot chamber  464  and the second pilot chamber  466 . When the inlet valve piston  416  is in the closed position there is no fluid communication between the high pressure chamber  432  and the central chamber  414  and there is no flow of high pressure concentrate from the inlet end  404  into the central chamber  414 . 
     During the outlet phase, the control unit  100  causes the outlet actuator  520  to provide pressure to the face of the outlet pilot valve piston  558 , which causes the outlet pilot valve stem  560  to physically direct the outlet pilot ball valve  570  into the outlet pilot valve seat  574 , the outlet position. The physical force of the outlet pilot valve stem  560  directing the outlet pilot ball valve  570  into the outlet position is greater than the hydrostatic pressure of the concentrate as it exits the port  242  and acts upon the outlet pilot ball valve  570  via the third pilot chamber  564 . While the outlet pilot ball valve  570  is in the outlet position, the second outlet pilot chamber  566  is in fluid communication with the third outlet pilot chamber  564 . The hydrostatic pressure of the concentrate within the pressure chamber  532  acting upon the outer ring  525  of the outlet valve piston  516  is greater than the total amount of force acting on the first surface  519 , the outlet valve piston  516  is displaced from the outlet valve seat  518  and the concentrate exiting the concentrate working chamber of the water cylinder  200  flows from the central chamber  414  to the outlet end  406  of the concentrate valve body  400 . 
     This written description uses examples to disclose the invention, including the best mode, to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art.