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Water-Source Heat Pump

See also: Categories: Swimming Pool Equipment, Pool Heating


A Water-Source Heat Pump refers to a swimming pool heat pump as well as a geothermal heat pump that transfers heat from a water-source to the swimming pool water.


Water-source heat pumps embrace newer technology, and therefore are not as widely-used as other types of heating systems. This type of heating systems is growing in popularity due to high efficiency and low operating costs.

How it works

A water-source swimming pool heat pump, also referred to as a geothermal heat pump, transfers heat from a water-source to your swimming pool water. Source water enters the unit and passes over an evaporator coil, which contains a cold liquid refrigerant, often referred to as “Freon.” As the source water passes over the coil, the refrigerant heats to become warm Freon gas. The source water cools, exits the evaporator, and travels back to the water source. The warm Freon gas passes through a compressor, which compresses it to hot Freon gas. Then, this hot Freon gas passes through a condenser, which is where the swimming pool water enters and exits the unit. The swimming pool water washes over the coil, heats, and leaves the unit warm. As heat transfers from the coil to the swimming pool water, the hot Freon gas cools to once again become cold refrigerant, and the process starts again

Water-Source System

Because many types of bodies of water exist, many types of water-source heat pumps exist. Some common water-source systems are explained below.

An open loop, also known as a deep ground well, consists of two deep wells: one that supplies water to the heat pump and one that returns water back to the ground. How can you tell if your well is deep enough? The bottoms of deeps wells should be within porous rock-based soil. By contrast, the bottoms of shallow wells are typically within sandy soil. A shallow well is subject to rapid draw down and clogging from loose soil.

A closed loop, also known as a ground loop, uses the ground as the heat source, rather than the water itself. In this system, plastic tubing is placed underground. A mixture of water and glycol (an antifreeze) circulates through the tubing and collects heat from the ground. The heated mixture returns to the heat pump to heat the evaporator coil. A closed loop system can be either shallow and wide (called a horizontal closed group) or deep and narrow (called a vertical closed group). A surface water system is a type of open loop system. This system draws water from an open body of water. Keep in mind, however, that higher maintenance is required to keep the water-to-refrigerant heat exchangers free of fouling from organic materials. Either fresh water-sources or salt-based water sources can be used. We do not recommend salt-based water-sources because barnacles and sea mussels can clog the plumbing system and cause a need for equipment replacement.

A mechanical loop is part of a large system that uses water to remove heat from a commercial air conditioning system. As the air conditioning system removes “waste” heat from indoors, it transfers it into a water loop. This loop is then cooled using a rooftop cooling tower. A water-source heat pump helps the air conditioning system operate more efficiently by tapping into this loop and removing this “waste” heat from the air conditioning system.

A pool/spa loop transfers heat from unheated swimming pools to spas. Because of the large size of a swimming pool, you can transfer enough heat from a swimming pool to warm a spa without noticeable decreasing the swimming pool’s temperature. Specifically, you can use a 50°F (10°C) swimming pool warm a spa to 104°F (40°C).

Advantages of Water-Source Heat Pumps

With their Coefficient of Performance measuring between 5 and 6, heat pumps offer very efficient heating.

  • Because of their high Coefficient of Performance, heat pumps have very low operating costs.
  • Water-source heat pumps operate independently of air temperature.
  • The life span of heat pumps is typically ten years.
  • Because heat pumps only use electricity to transfer energy and emit no pollution, they are very environmentally-friendly

Disadvantages of Water-Source Heat Pumps

  • Heat pumps have high upfront costs
  • Heat pumps offer slower heating than gas heaters.

Quick Facts

  • Water source heat pumps greatly benefit consumers who live in climates where the average air temperature is below 60°F (15.5°C) and consumers who use their swimming pools year-round.
  • Heat pumps typically cost between $50 and $150 per month to operate.

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