You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 61/894,008, filed Oct. 22, 2013, and having the same title as appears above, the entire contents of which application are incorporated herein by this reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to systems principally—although not necessarily exclusively—for cleaning recirculating water of recreational vessels such as swimming pools and spas (sometimes collectively referred to herein as “pools” or “swimming pools”) and more particularly, although again not exclusively, to systems utilizing variable-speed, dedicated booster pumps in connection with “pressure-side” automatic swimming pool cleaners (APCs). 
       BACKGROUND OF THE INVENTION 
       [0003]    Conventionally, APCs are categorized as either hydraulic or electric, depending mainly on the source of energy used to move the devices within pools. Hydraulic APCs frequently are sub-categorized as “suction-side” or “pressure-side” cleaners, with suction-side cleaners typically being connected, via hoses and debris filters, to inlets of water-recirculation pumps. Because this latter type of cleaner is connected to the suction side of the pump, it is evacuated by the pump and thus sucks debris-laden water from the pool to clean it. 
         [0004]    Pressure-side cleaners, by contrast, communicate with outlets of the pumps. Pressurized water thus is passed through the bodies of these cleaners; employing the Venturi principle, the pressurized water draws with it debris-laden water from the pool. The debris-laden water then passes through a filter before being returned to the pool. 
         [0005]    Standard water-recirculation pumps often are inadequate to power pressure-side APCs satisfactorily. Historically, therefore, separate booster pumps have been required to do so. U.S. Pat. No. 8,297,920 to Ortiz, et al., whose contents are incorporated herein in their entirety, discloses examples of such booster pumps. These booster pumps undeniably use additional electricity, a disadvantageous result especially as energy costs increase. 
         [0006]    Additionally, conventional booster pumps operate at a single speed. They thus may supply to pressure-side APCs water at greater pressure and/or volume than optimal or otherwise desirable. To resolve this problem, water by-pass paths may be created or restrictor plates may be placed in supply hoses, for example. Both approaches simply waste some of the pressure provided by the booster pumps, however, and therefore waste some of the energy used to pressurize the water. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention avoids the inefficiencies present in existing solutions involving single-speed booster pumps. Systems of the invention control speed and suction power of pressure-side APCs by varying the water flow supplied by the secondary booster pump rather than wasting extra flow by by-passing or restricting it. Preferred embodiments of the invention do so by employing a variable-speed booster pump and adjusting its motor speed (revolutions per minute, or RPMs) to supply a pressure-side APC with water at satisfactory, if no optimal, pressure and/or volume. No by-pass or restriction is thus necessary, materially reducing the amount of wasted energy. 
         [0008]    The present invention hence relates to systems including both pressure-side APCs and variable-speed pumps, especially booster pumps. It also relates to methods of cleaning pools using pressure-side APCs connected to outlets of variable-speed booster pumps. It further relates to pressure-side APCs configured for use with variable-speed booster pumps. Other objects, features, and advantages of the present invention will be apparent to those skilled in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]    The FIGURE is a block diagram of an exemplary water-circulation and cleaning system for a swimming pool or spa. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Illustrated in the FIGURE is an example of system  10  consistent with the present invention. Included in system  10  are filtration pump  20 , water distribution equipment  40 , and booster pump  50 . Optionally forming part of system  10  may be first and second water conditioning equipment  30  and  70 , respectively, and APC  60 , Although APC  60  is an optional part of system  10 , its presence is preferable, as inclusion of certain hydraulic APCs generates need for booster pump  50  (as discussed above). 
         [0011]    Filtration pump  20  constitutes the main water-circulation means for system  10 . Filtration pump  20  evacuates water from a swimming pool or spa (optionally through a skimmer or other filtration device) and passes the now-pressurized water at least to distribution equipment  40  downstream thereof. Optionally positioned upstream of distribution equipment  40  may be first water conditioning equipment  30 , which if present and operational may treat or sense characteristics of water exiting filtration pump  20  before it reaches distribution equipment  40 . Non-limiting examples of first water conditioning equipment  30  equipment may be filters, heaters, chlorinators or other sanitizers, sensors, or other devices. Optionally positioned downstream of distribution equipment  40  may be second water conditioning equipment  70 ; it too may be or include such devices as filters, heaters, chlorinators or other sanitizers, or sensors, for example. 
         [0012]    As noted in the Ortiz patent, distribution equipment  40  may comprise a plumbing system or manifold configured to divide water flow  80  into at least two flows  80 A and  80 B. Flow  80 B travels to second water conditioning equipment  70 , if present, then returning to the pool or spa from which it originated. By contrast, flow  80 A passes to booster pump  50  for subsequent downstream travel to APC  60 . In system  10 , booster pump  50  is distinct from filtration pump  20  and dedicated to further pressurizing water for operation of APC  60 . 
         [0013]    Conventionally, filtration pump  20  has a motor operational at either a single speed (i.e. a single-speed motor) or varying speeds (i.e. a variable-speed motor). Examples of such pumps  20  include the Jandy FloPro pumps, available from Zodiac Pool Systems, Inc. with single- and variable-speed motors. Other commercially-available pool pumps may be used as filtration pump  20 . 
         [0014]    Well known in the pool and spa industry is that inclusion of booster pumps in pool and spa water-circulation systems undesirably adds to the energy usage of the systems. Yet, as noted earlier, conventional booster pumps operate at a single speed. This is true today, as even the booster pump of the recently-issued Ortiz patent is designed for single-speed operation. Long-needed, therefore, is a booster pump that allows operation of an APC (especially a pressure-side APC) but reduces, to the extent feasible, the additional energy needed to function. 
         [0015]    Booster pump  60  of system  10  fulfills this long-felt need in the industry by configuring its motor to operate at varying speeds. It thus may be constructed using at least some of the variable-speed technology of the corresponding Jandy FloPro pumps, for example, although other variable-speed motors and technology may be used instead. Generally, booster pump  60  will be both physically smaller and less powerful than filtration pump  20 , although these differences are not necessarily required. 
         [0016]    Hence, even if filtration pump  20  has a single-speed motor, system  10  allows variation in water flow and pressure to APC  60  by adjusting motor speed of booster pump  60 . In this way, system  10  may supply water to APC  60  at optimal (or near optimal) pressures and/or volumes without need for energy-wasting by-pass paths or restrictor plates. Moreover, for systems  10  in which both filtration pump  20  and booster pump  50  utilize variable-speed motors, speeds of both motors may be adjusted independent of one another to improve overall efficiency of operation of the systems  10 . 
         [0017]    The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of the present invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of the invention. For example, persons skilled in the art will recognize that booster pump  50  is not necessarily limited to use with pressure-side APCs  60  and that system  10  may be configured and plumbed differently so as to allow use of booster pump  50  with another type of hydraulic APC  60  or otherwise as desired. Hoses, conduits, pipes, and other conventional equipment may be used to pass water between components of system  10 .

Summary:
Systems and methods for circulating water of swimming pools or spas are detailed. The systems may include both a main filtration pump and a secondary booster pump, with the booster pump containing a variable-speed motor. By adjusting motor speed of the booster pump, pressurized water may be supplied to certain automatic swimming pool cleaners more efficiently, without need for energy-wasting by-pass paths or restrictor plates.