document: CROSS-REFERENCE TO RELATED APPLICATIONS 
         [0001]    This application claims the benefit of U.S. patent application 62/055,020, filed Sep. 25, 2014, the contents of which are incorporated herein by reference. 
       
      
       FIELD 
         [0002]    This application relates to pumps, in particular to pumps for pumping fluids. 
         BACKGROUND 
         [0003]    Liquid manure from animal husbandry operations, particularly pig farming operations, is typically stored in a large manure reservoir or lagoon until there is a sufficient quantity available to spread or irrigate onto farm land for disposal. In order to remove the manure from the reservoir, a pump is used that is typically located alongside the reservoir and lowered into the reservoir. The pump can be free standing or attached to a tractor, which is often preferable to provide stability to the pump and a source of motive power for the pump. 
           [0004]    A pump for pumping fluids at high volumetric flow rate (e.g. in excess of 4000 gal/min), particularly for pumping liquid manure from a reservoir, has been previously described in U.S. Patent Publication 2012/0224982 published Sep. 6, 2012, the contents of which is herein incorporated by reference. Such a pump has large fluid openings and generous tolerances in order that solid material in the reservoir can be accommodated by the pump without plugging. While excellent for pumping high volumes of fluid, such a pump generally operates at low pressure. For some applications, it may be desirable to not only pump fluid at high volumetric flow rate, but to also pump the fluid under high pressure. 
           [0005]    Accordingly, there still exists a need for improved pumps, particularly pumps capable of pumping fluids at high volumetric flow rate and high pressure. 
         SUMMARY 
         [0006]    In one aspect, there is provided a fluid pump comprising: a first pump head comprising a first housing containing a first impeller configured to move fluid through at least three first conduits in fluid communication with the first housing; a second pump head comprising a second housing containing a second impeller configure to move fluid through at least three second conduits in fluid communication with the second housing, the at least three second conduits in fluid communication with an inlet into the first housing along a fluid flow path between the first and second pump heads, the at least three second conduits combining fluid flow therethrough at the inlet to provide a single flow of fluid through the inlet into the first housing; and, a drive structure passing through the inlet between the first and second pump heads, the drive structure configured to commonly drive the first and second impellers. 
           [0007]    In another aspect, there is provided a fluid pump comprising: a first pump head comprising a first housing containing a first impeller configured to move fluid through at least three first conduits in fluid communication with the first housing; a second pump head comprising a second housing containing a second impeller configured to move fluid through at least three second conduits in fluid communication with the second housing; a third pump head disposed between and in fluid communication with the first and second pump heads, the third pump head comprising a third housing containing a third impeller configured to move fluid through at least three third conduits in fluid communication with the third housing, the at least three third conduits in fluid communication with an inlet into the first housing along a first fluid flow path between the first and third pump heads, the at least three third conduits combining fluid flow therethrough to provide a single flow of fluid through the inlet into the first housing, the at least three second conduits in fluid communication with an inlet into the third housing along a second fluid flow path between the second and third pump heads, the at least three second conduits combining fluid flow therethrough to provide a single flow of fluid through the inlet into the third housing; and, a drive structure passing through the inlet into the first housing and the inlet into the third housing, the drive structure configured to commonly drive the first, second and third impellers. 
           [0008]    In another aspect, there is provided a fluid pump comprising: a first pump head comprising a first housing containing a first impeller configured to move fluid through at least two first conduits in fluid communication with the first housing; a second pump head comprising a second housing containing a second impeller configured to move fluid through at least two second conduits in fluid communication with the second housing, the at least two second conduits in fluid communication with an inlet into the first housing along a fluid flow path between the first and second pump heads, the at least two second conduits combining fluid flow therethrough at the inlet to provide a single flow of fluid through the inlet into the first housing; and, a drive structure passing through the inlet between the first and second pump heads, the drive structure configured to commonly drive the first and second impellers. 
           [0009]    In another aspect, there is provided a pump head for connecting two other pump heads in a fluid pump having at least three pump heads, the pump head comprising: a combiner comprising a fluid chamber in which fluid flow from at least two conduits are combined into a single flow of fluid that flows out of the chamber along a first fluid flow path into an inlet in a first neighboring pump head; a housing containing an impeller configured to move fluid through the at least two conduits in fluid communication with the housing, the housing comprising an inlet for receiving a single flow of fluid along a second fluid flow path from a second neighboring pump head; a drive structure passing through the first and second fluid flow paths connectable to drive structures of the first and second neighboring pump heads, the drive structure configured to commonly drive the impeller with impellers in the first and second neighboring pump heads; the combiner further comprising a first structure connectable to the first neighboring pump head; and, the housing further comprising a second structure connectable to a second neighboring pump head. 
           [0010]    In another aspect, there is provided a pump assembly comprising a fluid pump as described above. 
           [0011]    The fluid pump comprises two or more pump heads configured in series so that fluid being pumped moves from a reservoir into one pump head and thence to the next pump head in the series, to be eventually discharged from an outlet in a final pump head. Each pump head comprises a housing within which an impeller is contained, the impeller being driven by the drive structure to move fluid. The housing of the pump head comprises an inlet through which fluid is drawn from outside the housing, and the fluid is moved by the impeller from the housing into at least two fluid conduits, preferably at least three fluid conduits, more preferably three or four fluid conduits, to be combined into one fluid flow before exiting the pump head. One or more of the pump heads may comprise a combiner for combining fluid flow from the at least two fluid conduits into a single fluid flow. The combiner may comprise a fluid chamber in which fluid flow from the at least two conduits are combined into the single flow. The fluid chamber of the combiner may comprise openings to permit entry of the fluid from the conduits, and another opening to permit a single outward flow of the fluid from the pump head. The single flow of fluid from one pump head into another defines a fluid flow path between the pump heads. 
           [0012]    The drive structure may comprise any one or collection of structures that is configured to impart rotational motion on the impellers. Although more than one power source may be employed, preferably, the drive structure is powered by a single power source, for example a suitable motor. The motor may be, for example, an electric motor, a hydraulic motor, a combustion motor or any other motor that can be configured to drive the drive structure. In one embodiment, the drive structure may comprise one or more drive shafts on which the impellers are mounted. Where there is a single drive shaft, all of the impellers may be mounted on the single drive shaft. Where there are two or more drive shafts, there may be at least one impeller mounted on each drive shaft. 
           [0013]    Where there are two or more drive shafts, the drive shafts may be connected through one or more connectors so that one or more of the drive shafts may receive rotational motion from another of the drive shafts. Any one connector may be mounted on two separate drive shafts. Or any one connector may be mounted at one end on a drive shaft and at another end on an impeller, which is mounted on a drive shaft. Or any one connector may be mounted at two ends on separate impellers, which are mounted on respective drive shafts. When a connector is mounted on an impeller, the connector and impeller may form a unitary structure or may be removably connected. Connectors may extend out from the pump heads so that the connector bridges two pump heads and is partially disposed in one or both of the pump heads. In one embodiment, a connector may extend out through the inlet of one pump head. In one embodiment, a connector may extend out through an opening in a combiner of one pump head. In one embodiment, a connector may extend out through the inlet of one pump head and out through an opening in a combiner of a neighboring pump head. In one embodiment, at least a portion of each of the one or more connectors may be in the fluid flow path between respective pump heads. 
           [0014]    In one embodiment, any one connector may comprise a sleeve within which one or both of the drive shafts is rigidly mounted to permit transmission of rotational motion from one drive shaft to the other. In one embodiment, one or both of the drive shafts may be frictionally mounted within the connector. In one embodiment, connector may be cylindrical, while in another embodiment the connector may be a tube having a central portion between two end portions, the end portions having larger diameters than the central portion. 
           [0015]    Drive shafts within a pump head may extend out from the pump head in one or more directions or may be wholly contained within the pump head. Preferably, the drive shaft does not extend out through the inlet of the housing. Where two drive shafts are connected by a connector, the ends of the drive shafts being connected preferably do not extend outside the pump head. For an initial pump head where fluid is first drawn from a reservoir, the pump head may comprise an impeller having a closed cap configured to seat an end of the drive shaft. 
           [0016]    The fluid pump comprises at least two pump heads, for example two, three or four pump heads. The pump heads are disposed in series so that fluid flows sequentially through each pump head of the pump, each pump head being in fluid communication with the pump head before and after in the series. The initial and final pump heads are in direct fluid communication with only one other pump head, the initial pump head drawing fluid from a reservoir in through an inlet in the housing of the initial pump head, and the final pump head expelling fluid out through an outlet of the final pump head. Pump heads may be connected to provide rigidity and a fluid seal between the pump heads. The pump heads may be removably connected or may be formed in a unitary structure. Removable connection of the pump heads permits modularity, thereby facilitating repair should one of the pump heads fail and facilitating the inclusion of more pump heads in the series. Inclusion of more pump heads increases the operating pressure of the pump, which can be tailored by adjusting the number of pump heads in the pump. 
           [0017]    As described herein, the fluid pump cannot be constructed by simply stacking known pumps together. The initial and final pump heads have different design features to permit fluid flow from one pump head to the other, while commonly driving the impellers. Intermediate pump heads have design features of both the initial and final pump heads to permit the intermediate pump heads to cooperate with neighboring pump heads to permit series flow of fluid and common driving of the impellers. 
           [0018]    A pump assembly comprises a fluid pump mounted on a support structure. The support structure may comprise any suitable apparatus that permits operation of the pump at a fluid reservoir. Some examples of support structures include a wheeled boom, a hitching assembly and a trailer. A wheeled boom may be configured to be towed behind a vehicle, for example a tractor or a truck, and configured to permit submersing the pump into a fluid reservoir. A hitching assembly may be configured to be attached to moveable arms to permit submersing the pump into a fluid reservoir. The hitching assembly maybe associated with a vehicle, for example a tractor or a truck, and the moveable arms powered by a hydraulic system on the vehicle. A trailer may be configured with a trailer bed on which the fluid pump rests, and a submersible pipe in fluid communication with the housing of the initial pump head may be configured to be immersed in a fluid reservoir to permit transfer of fluid from the reservoir into the initial pump head. 
           [0019]    Further features will be described or will become apparent in the course of the following detailed description. It should be understood that each feature described herein may be utilized in any combination with any one or more of the other described features, and that each feature does not necessarily rely on the presence of another feature except where evident to one of skill in the art. 
       
      
       
         BRIEF DESCRIPTION OF THE DRAWINGS 
           [0020]    For clearer understanding, preferred embodiments will now be described in detail by way of example, with reference to the accompanying drawings, in which: 
             [0021]      FIG. 1A  is an elevation view of a first embodiment of a fluid pump having two pump heads in series and three fluid conduits per pump head; 
             [0022]      FIG. 1B  is a top end view of the pump of  FIG. 1A ; 
             [0023]      FIG. 1C  is a side view of the pump of  FIG. 1A ; 
             [0024]      FIG. 1D  is a side cross-section view of the pump of  FIG. 1A  taken through section A-A shown in  FIG. 1B ; 
             [0025]      FIG. 2A  is an elevation view of one embodiment of an impeller useable in a first pump head of a fluid pump of the present invention; 
             [0026]      FIG. 2B  is an elevation view of one embodiment of an impeller useable in a second pump head of a fluid pump of the present invention; 
             [0027]      FIG. 3A  is an elevation view of one embodiment of a combiner for a pump head in a fluid pump of the present invention; 
             [0028]      FIG. 3B  is a side view of the combiner of  FIG. 3A ; 
             [0029]      FIG. 3C  is a top view of the combiner of  FIG. 3A ; 
             [0030]      FIG. 3D  is a side view of the combiner of  FIG. 3A  viewed from an angle of 90-degrees with respect to the view in  FIG. 3B ; 
             [0031]      FIG. 4A  is side view of a second embodiment of a fluid pump having three pump heads in series and three fluid conduits per pump head; 
             [0032]      FIG. 4B  is a top view of the pump of  FIG. 4A ; 
             [0033]      FIG. 4C  is a cross-section view of the pump of  FIG. 4A  taken through section B-B shown in  FIG. 4B ; 
             [0034]      FIG. 5  depicts the pump of  FIG. 1A  mounted on a wheeled boom; 
             [0035]      FIG. 6  depicts the pump of  FIG. 1A  mounted on a hitching assembly; and, 
             [0036]      FIG. 7  depicts the pump of  FIG. 1A  mounted on a trailer. 
         
      
      
       DETAILED DESCRIPTION 
         [0037]      FIGS. 1A-1D  depict one embodiment of a fluid pump  1  of the present invention comprising two pump heads  10 ,  50  arranged in series so that fluid being pumped from a reservoir passes through second pump head  50  into first pump head  10  to be discharged out of first pump head  10  into a desired location, for example into a holding tank. 
           [0038]    The second pump head  50  comprises a second housing  51  within which a second impeller  53  is mounted on a second drive shaft  55 . The second drive shaft  55  is parallel to and concentric with a longitudinal axis L of the pump  1 , although an eccentric arrangement may be used, and in some cases the drive shaft may form an oblique angle with longitudinal axis L. The second impeller  53  being driven by rotation of the second drive shaft  55  draws fluid from a fluid reservoir located outside the pump  1 , the fluid entering the second housing  51  through a second inlet  56  (as best seen in  FIG. 1D ) in a base  57  of the second housing  51 . The second inlet  56  is ringed by an inlet ring  58  surrounding a perimeter of the second inlet  56 . The inlet ring  58  may be used to mount an immersion pipe to the pump  1 . Fluid flows into the second housing  51  through the second inlet  56  in a single flow in a flow path parallel to a path defined by the longitudinal axis L of the pump  1 . At a periphery of the second housing  51 , three ports lead from an interior of the second housing  51  to three outwardly extending curved second fluid conduits  59 . Fluid flows tangentially and outwardly from the second housing  51  into the second fluid conduits  59 , the fluid thereby being diverted away from the longitudinal axis L of the pump  1 . Fluid flowing in the three second fluid conduits  59  is combined into a single fluid flow at second combiner  61  where the three second fluid conduits  59  meet to form a second chamber  63  through which the longitudinal axis L passes. Fluid from the second chamber  63  passes through a second outlet  65  in a single flow in a flow path parallel to a path defined by the longitudinal axis L of the pump  1 . The single flow of fluid passing out of the second outlet  65  of the second combiner  61  is preferably along the longitudinal axis L, more preferably concentric with the longitudinal axis L. The second housing  51  may further comprise a second housing extension  52  that serves to further enclose the second drive shaft  55  and any seals (e.g. O-rings), bearings or other components of the second pump head  50 . The second housing extension  52  may also serve to support the second combiner  61  to provide extra rigidity and strength. 
           [0039]    The first pump head  10  comprises a first housing  11  within which a first impeller  13  is mounted on a first drive shaft  15 . The first drive shaft  15  is parallel to and concentric with a longitudinal axis L of the pump  1 , although an eccentric arrangement may be used, and in some cases the drive shaft may form an oblique angle with longitudinal axis L. The first impeller  13  being driven by rotation of the first drive shaft  15  draws fluid from the second chamber  63  of the second combiner  61 , the fluid entering the first housing  11  through a first inlet  16  (as best seen in  FIG. 1D ). Fluid flows into the first housing  11  through the first inlet  16  in a base  27  of the first housing  11  in a single flow in a flow path parallel to a path defined by the longitudinal axis L of the pump  1 . The single flow of fluid passing through the first inlet  16  into the first housing  11  is preferably along the longitudinal axis L, more preferably concentric with the longitudinal axis L. At a periphery of the first housing  11 , three ports lead from an interior of the first housing  11  to three outwardly extending curved first fluid conduits  19 . Fluid flows tangentially and outwardly from the first housing  11  into the first fluid conduits  19 , the fluid thereby being diverted away from the longitudinal axis L of the pump  1 . Fluid flowing in the three first fluid conduits  19  is combined into a single fluid flow at first combiner  21  where the three first fluid conduits  19  meet to form a first chamber  23 . The longitudinal axis L of the pump  1  does not pass through the first combiner  21  or the first chamber  23 . Fluid from the first chamber  23  passes through a first outlet  25  in a single flow in a flow path oblique to, for example perpendicular to, a path defined by the longitudinal axis L of the pump  1 . The first housing  11  may further comprise a first housing extension  12  that serves to further enclose the first drive shaft  15  and any seals (e.g. O-rings), bearings or other components of the first pump head  10 . 
           [0040]    The first and second pump heads  10 ,  50  are connected to each other so that the second outlet  65  of the second combiner  61  is in direct fluid communication with the first inlet  16  of the first housing  11 . To connect the two pump heads  10 ,  50 , the second combiner  61  may be attached to the base  27  of the first housing  11 , for example by bolting, although any sufficiently secure attachment arrangement may be used. 
           [0041]    Referring especially to  FIG. 1D , the first and second pump heads  10 ,  50  are arranged so that the first and second drive shafts  15 ,  55  are longitudinally aligned, preferably along the longitudinal axis L of the pump  1 . This arrangement also longitudinally aligns the flow path of the single flow of fluid into the second housing  51  with the flow path of the single flow of fluid into the first housing  11 . In order to commonly drive the first and second drive shafts  15 ,  55 , the first and second drive shafts  15 ,  55  are connected by a biconical tubular connector  70 . The biconical tubular connector  70  bridges the first and second pump heads  10 ,  50  extending through the first inlet  16 , through the second outlet  65  and through the second chamber  63  of the second combiner  61  to frictionally secure one end of the second drive shaft  55  in a hollow interior of the tubular connector  70 . Thus, the tubular connector  70  is within the fluid flow path between the two pump heads  10 ,  50 . The tubular connector  70  prevents fluid flowing from the second chamber  63  of the combiner  61  through the first inlet  16  into the first housing  11  from entering into a drive train comprising the tubular connector  70  and first and second drive shafts  15 ,  55  thereby protecting the drive shafts  15 ,  55  from corrosion and befouling. Frictionally securing the second drive shaft  55  in the tubular connector  70  permits removing the second drive shaft  55  from the tubular connector  70 , which contributes to modularity as the first and second pump heads  10 ,  50  are then more easily separated should the need arise for maintenance on one of the pump heads or for inserting more pump heads between the first and second pump heads. 
           [0042]      FIG. 2A  provides a magnified view of the biconical tubular connector  70  illustrating that in this embodiment, a first end  71   a  of the tubular connector  70  is integrally formed with the first impeller  13  to provide extra strength to withstand torsional forces created when the first impeller  13  and tubular connector  70  are rotationally driven by the first drive shaft  15  on which the first impeller  13  is mounted. A second end  71   b  of the tubular connector  70  has an opening  72  through which the second drive shaft  55  may be inserted, the second drive shaft  55  being frictionally secured within the tubular connector  70 . The first drive shaft  15  extends out of the first housing extension  12  to be operatively connected to a drive motor (not shown). Driving the first drive shaft  15  with the motor causes rotation of the first drive shaft  15 , thereby causing rotation of the first impeller  13  mounted on the first drive shaft  15 , thereby causing rotation of the tubular connector  70  integrally formed with the first impeller  13 , thereby causing rotation of the second drive shaft  55  frictionally secured in the tubular connector  70 , thereby causing rotation of the second impeller  53  mounted on the second drive shaft  55 , which results in the two impellers  13 ,  53  being commonly driven. Thus, the entire drive train is longitudinally aligned with the longitudinal axis L of the pump  1 , and the drive train passes through the fluid flow path of the fluid flowing between the first and second pump heads  10 ,  50 . 
           [0043]    Still referring to  FIG. 1D , second drive shaft  55  has an end that extends into the second housing  51  but does not protrude out of the second inlet  56 . At this end, the second drive shaft  55  is capped with a bell-shaped cap  80  to prevent fluid from entering into the drive train thereby protecting the drive shaft  15  from corrosion and befouling.  FIG. 2B  provides a magnified view of the bell-shaped cap  80  showing that the bell-shaped cap  80  may be integrally formed with the second impeller  53 . Both  FIG. 2A  and  FIG. 2B  illustrate impellers having five arcuate vanes. The first impeller  13  comprises five arcuate vanes  14  (only one labeled) and the second impeller  53  comprises five arcuate vanes  54  (only one labeled). There may be more or less vanes and the vanes may be of another shape, however, such an impeller arrangement as shown in  FIG. 2A  and  FIG. 2B  is efficient for moving fluid tangentially outwardly to the ports and thence to the outwardly extending curved fluid conduits. 
           [0044]    The second combiner  61  is configured for direct fluid communication with the first inlet  16  of the first housing  11 . As illustrated in  FIGS. 1A-1D  and  FIGS. 3A-3D , the second combiner  61  comprises a mounting plate  67 , which is shaped and configured to be secured to the base  27  of the first housing  11 . The second combiner  61  may also comprise a combiner extension  68  configured to be secured to the second housing extension  52  so that the second combiner  61  may be detached from the second housing  61 . The mounting plate  67  and the combiner extension  68  contribute to modularity and ease of assembly of the second pump head  50  and pump  1 . At the second combiner  61 , the second fluid conduits  59  meet to form second chamber  63  where fluid combines before flowing out through the second outlet  65 . The fluid conduits, including one or both of the first and second fluid conduits  19 ,  59 , and any one or more of the fluid conduits for a particular pump head, may be formed in a unitary manner or may be formed of segments of conduits to facilitate assembly of the pump  1 . 
           [0045]      FIGS. 4A-4C  depict another embodiment of a fluid pump  2  of the present invention comprising three pump heads  10 ,  50 ,  100  arranged in series so that fluid being pumped from a reservoir passes through second pump head  50  into third pump head  100  and then into first pump head  10  to be discharged out of first pump head  10  into a desired location, for example into a holding tank. 
           [0046]    The first and second pump heads  10 ,  50  are as described above for the fluid pump  1 . The third pump head  100  is the same as the second pump head  50 , except that third inlet  116  of the third pump head  100  is designed like the inlet  16  of the first pump head  10 . Thus, the third inlet  116  is not ringed by an inlet ring such as the inlet ring  58  on the second pump head  50 . Further, third drive shaft  115  in the third pump head  100  aligns with both the first drive shaft  15  and the second drive shaft  55 , with a third impeller  113  in a third housing  111  of the third pump head  100  comprising a second biconical tubular connector  170  formed as a unitary structure with the third impeller  113 . The second drive shaft  55  is frictionally secured in the second biconical tubular connector  170 . Thus, unlike in the second pump head  50 , the third drive shaft  115  in the third housing  111  of the third pump head  100  is not capped by a bell-shaped cap. Furthermore, the biconical tubular connector  70 , which is integrally formed with the first impeller  13  has an end of the third drive shaft  115  frictionally secured therein. Thus, the entire drive train is collinear along longitudinal axis L′ and all of the impellers may be commonly driven by one motor. One or more additional pump heads identical in construction to the third pump head  100  may be inserted into the series of pump heads to provide a pump with greater operating pressure. 
           [0047]    A pump assembly may be formed by mounting a fluid pump of the present invention on a support structure. The support structure may comprise any suitable apparatus that permits operation of the fluid pump at a fluid reservoir. Some examples of support structures include a wheeled boom, a hitching assembly and a trailer. 
           [0048]      FIG. 5  depicts the fluid pump  1  described above mounted on a first end of a boom  201 . The boom  201  comprises two sets of wheels  204  mounted on the boom  201  through a wheel frame  205  proximate the first end of the boom  201  to form a wheeled boom. A second end of the boom  201  comprises a towing hitch  206  for securement to a vehicle for transporting the wheeled boom with the pump from location to location. An elongated fluid conduit  202  extending between the first and second ends of the boom  201  is in fluid communication with the outlet of the first pump head  10  and carries pumped fluid from the fluid pump  1  to a tank (not shown) or some other fluid holding apparatus. The outlet of the first pump head  10  is also in fluid communication with agitator nozzle  209  so that a portion of the fluid being pumped is directed through the agitator nozzle  209  to be sprayed back into the fluid reservoir in order to encourage mixing of the fluid in the fluid reservoir. The agitator nozzle  209  is configured to be moveable so that the nozzle  209  may be pointed in a desired direction. 
           [0049]      FIG. 6  depicts the fluid pump  1  described above mounted on a hitching assembly  220 . The hitching assembly  220  comprises a pump support  211  on a first end of which the pump  1  is mounted. A second end of the pump support  211  is pivotally mounted on two arms  221 , each of the two arms  221  comprising mounting brackets  224  for mounting the hitch assembly  220  on a vehicle. Hydraulic cylinders  222  actuatable from a cab of the vehicle retract or extend to permit pivoting of the pump support  211  around pivot rod  223  extending between the arms  221 . Pivoting of the pump support  211  permits raising the pump  1  out of a fluid reservoir, or lowering the pump  1  into the fluid reservoir. An elongated fluid conduit  202  extending between the first and second ends of the pump support  211  is in fluid communication with the outlet of the first pump head  10  and carries pumped fluid from the fluid pump  1  to a tank (not shown) or some other fluid holding apparatus. The outlet of the first pump head  10  is also in fluid communication with agitator nozzle  209  so that a portion of the fluid being pumped is directed through the agitator nozzle  209  to be sprayed back into the fluid reservoir in order to encourage mixing of the fluid in the fluid reservoir. The agitator nozzle  209  is configured to be moveable so that the nozzle  209  may be pointed in a desired direction. 
           [0050]      FIG. 7  depicts the fluid pump  1  described above mounted on a trailer  230 . The fluid pump  1  rests on a trailer bed  231 , the trailer bed  231  also supporting a motor unit  240  for driving the drive train of the fluid pump  1 . Attached to the inlet ring  58  of the second pump head  50  of the pump  1  is a feed pipe  235  in fluid communication with the inlet into the second pump head  50 . The fed pipe  235  may bifurcate into two immersion pipes  236 , 237 , which can be extended to be immersed in the fluid reservoir to provide two fluid flows into the feed pipe  235 . A vent pipe  238  extending upwardly from the feed pipe  235  and in fluid communication with the feed pipe  235  and open to the atmosphere ensures that pressure in the feed pipe  235  does not become excessive. The motor assembly  240  drives the drive train of pump  1  to draw fluid from the reservoir (not shown) which is ultimately discharged through the first outlet  25  of the first pump head  10  into a fluid conduit (not shown) and then into a holding tank (not shown) or some other fluid holding apparatus. 
           [0051]    The novel features will become apparent to those of skill in the art upon examination of the description. It should be understood, however, that the scope of the claims should not be limited by the embodiments, but should be given the broadest interpretation consistent with the wording of the claims and the specification as a whole.
summary: A fluid pump having at least two pump heads in series permits pumping fluid at both high pressure and high volumetric rate. Each pump head has at least two fluid conduits in fluid communication with a housing, the housing containing an impeller for drawing fluid through an inlet in the housing and moving the fluid through the fluid conduits. The at least two fluid conduits of one pump head combine fluid flow at the inlet of a neighboring pump head to provide a single flow of fluid through the inlet into the neighboring pump head. A drive structure passing through the inlets between two pump heads is configured to commonly drive the impellers in the housing of each pump head.