Dedicated water-to-water heat pumps connected to a ground water source or a ground-coupled loop can be used for seasonally heating pools and hot tubs.
A word of caution: manufacturers may restrict their warrantees on their equipment on these applications.
Users must follow the instructions provided with the pool or hot tub for maintaining satisfactory water pH levels. If the pH is kept in the 6 to 8 range, preferably around 7, the heat pump should have a normal service life. If not, a separate water-to-water heat exchanger should be used. Otherwise, the heat pump service life will be much shorter.
Catastrophic failure of the water-to-refrigerant heat exchanger can allow chlorinated water to enter the refrigeration circuit. This can destroy the compressor and other major components resulting in a very expensive replacement. The heat pump's water circuit should take and return water from the piping between the pool pump and pool filter. A diverting valve can be used to assure a flow of 3 gpm per ton to the heat pump. A water thermostat can control the heat pump's operation to maintain minimum pool water temperature.