Lean MEG is a commonly used liquid in subsea facilities for hydrate inhibition, hydrostatic and leak testing, or holding in confined systems after subsea installation. However, the high thermal expansivity of MEG may lead to over-pressurisation in confined systems owing to small temperature increases in the surroundings, causing safety concerns. Accurate methods to predict thermally induced pressure rises, therefore, are essential for adequate sizing and operational management. This study assessed the performance of three equations of state (EoS) (Peng–Robinson PR78A, Cubic Plus Association (CPA-PR78A), and the high accuracy EoS CSMA). The physical properties considered in this study included density, isothermal compressibility and thermal expansivity of liquid water–MEG mixtures. The effect of the accuracy of these properties on prediction of thermally induced pressure rises in confined water–MEG subsea systems was then validated with field data. It was found that cubic and the cubic-related EoS significantly underpredict the liquid isothermal compressibility, leading to overprediction of the thermally induced pressure rise of liquid water–MEG mixtures in a confined subsea system. In contrast, the predictions of the liquid compressibility and the pressure rise by the high accuracy EoS CSMA are in good agreement with the measured field data. This confirms that the CSMA EoS is the better thermodynamic model for modelling pressure rise predictions for liquid water–MEG mixtures in confined subsea systems. Since salts are always present in subsea systems, their effect on the physical properties and simulated pressure rises were also investigated. It was found that the effect of salts on liquid density, compressibility and thermal expansivity may be correlated with salt concentration and treated as a perturbation to salt-free water–MEG mixtures. The effect of salts on the predicted pressure rise will provide valuable guidance to the industry.