'Ground Source Drilling' drill vertically down below the earth's surface, inserting a 32mm or 42mm pipe, whereby water is then circulated through the pipes. The water in the pipes is lower than the surrounding ground and so it warms up slightly. This low-grade heat is transferred to a heatpump, where it is used to heat up a refrigerant. By compressing this 'warmed' refrigerant further heat is generated and this means that water output from the heat pump is typically 45ºC - 50ºC. for space heating and up to 55ºC for domestic hot water.