# 2012 Barcelona
Heating and/or air conditioning systems based on ground heat pumps are increasingly popular in European countries, their growth fuelled by both private and public investments in sustainable energy sources. These systems typically circulate water inside boreholes, effectively using the ground as a constant temperature heat source or heat sink for their thermodynamic cycle. For boreholes reaching depths of up to a few hundred meters, heat exchangers are commonly made from high density polyethylene pipes & fittings systems. These geothermal probes must withstand the sum of hydrostatic and circulation pressures. To resist the effect of continuous pressure to which the pipes are submitted, high density bimodal polyethylene PE100 grades are of course a must for the geothermal application. Designed for 100 years of use and most often not accessible for maintenance during their lifetime, these pipes are also made to last. For this reason, this paper further shows that the material of choice for geothermal probes is PE100-RC, the latest generation of PE100 offering a superior resistance to slow crack growth. This characteristic allows stopping the crack propagation from scratches resulting from the handling of pipes in rough building area. It also allows the pressurized pipes to withstand continuous concentrated loads resulting from the installation procedure of the pipes in the borehole itself.