An open-loop system is used less frequently, but may be employed cost-effectively if ground water is plentiful. Open-loop systems in fact, are the simplest to install and have been used successfully for decades in areas where local codes permit. This type of system uses ground water from an aquifer and is piped directly from the well to the building, where it transfers its heat to a heat pump. After it leaves the building, the water is disposed of by one of three methods.
- Surface drainage – to a low area such as a pond, river, lake or stream, etc.
- Sub surface – to a dedicated drainfield sized to the required volume of water of the heat pump.
- Re-injection or discharge well - water is pumped back into the same aquifer through a separate discharge well.
Local environmental officials should be consulted whenever an open-loop system is being considered.
**The open-loop system is not allowed in Wisconsin.**
