Single speed pumps are the most common pumps found on pools until recently. They are usually in 115v/230v single phase configurations, although can also be found in 208/230 configurations as well as 3 phase options on larger pumps. These pumps operate at 1 speed, and are either ON or OFF. The majority of these pumps (more specifically the motors) will no longer be produced as of July of 2021. The main exception is the 1HP Hayward Super Pump. This is the only relevant single speed pump to meet the new energy efficiency requirements. All other single speed pumps such as the whisperflo, superflo, stealth, utilitec, etc. will need to be replaced by an appropriate VSF pump, once the current single speed motor is no longer operable.
2 Speed pumps are most frequently seen used in hot tubs. They are wired for a low speed and high speed mode. The low speed is designed for basic circulation/filtration purposes, as well as running the heater, while the high speed mode is to provide powerful jets when the hot tub is in use. These pumps will also require replacement with VSP/VSF pumps after July 2021 as per the US Dept. of Energy. VSP/VSF pumps offer greater control, as you can set the specific speeds/flow rates for the pump to operate at and does so with a much higher level of energy efficiency.
Variable Speed/Variable Flo pumps are the way of the future with pool pumps. They offer an incredible amount of versatility, energy efficiency and features. There are built in timers, giving you unprecedented control, and allowing you to run your pump at a higher speed during peak sunlight hours, and slow it down to conserve energy at night, while still continuing to filter, circulate, sanitize and heat when there is no need to run it at high speed. They are also very versatile in terms of deck sprayers, fountains, waterfalls, etc, and being able to program the pump for the correct adjusted flow as each water feature demands additional water. For commercial applications there are also SVRS models, which incorporate a self resetting vacuum release which is Virgina Baker Act compliant, to avoid the possibility of entrapment.