Polyethylene (PE) is a low-cost and versatile material for pipe applications. However, when it comes to at elevated temperatures, the use of PE is restricted due to its propensity to crack under stress and to undergo thermo-oxidative degradation reactions (ageing)1. Cross-linked polyethylene (PEX) has been appointed as a promising alternative to solve these limitations1. There are several different cross-linking processing methodologies for polyethylene pipes. The most usual methods are based on peroxide (PEX-a), silane (PEX-b) and irradiation (PEX-c). Additionally, photo-induced cross-linking (PEX-e), has recently garnered attracted significant commercial interest, but there is still very little information in the literature regarding this novel material. Recent findings appoint to hot water as being the key component element driving the ageing mechanism in PEX-a pipes used for hot water transportation. However, further investigation of the effects of ageing on PEX properties over time is of high importance. Accordingly, the present work aims to evaluate the properties of different types of PEX pipes as a function of ageing. PEX-a, two formulations of PEX-e and PE pipe samples were submersed in distilled water at 95°C for 150 days. Samples were removed periodically and the effect of degradation on the properties was measured by differential scanning calorimetry (DSC), oxidation induction time (OIT), dynamical mechanical thermal analysis (DMA) and tensile tests. Initial results showed that the OIT values for PEX-a before ageing were considerably lower than for the other materials but remained overall the same after 60 days of ageing. For the two formulations of PEX-e, a considerable decrease in OIT was observed, indicating that stabilizing additive hydrolysis was high for this PEX type under these conditions.