The spectral induced polarisation (SIP) characteristics of sedimentary rocks contain structural information which potentially can be linked to flow and transport parameters, such as hydraulic conductivity. We examined this connection for pure, saturated sands by measuring SIP spectra of sands with different grain size and pore water electrical conductivity. For each spectrum, relaxation times, chargeabilities and Cole-Cole exponents were determined for identified dispersion ranges under the assumption of superimposed Cole-Cole model responses. We here focus on the results concerning the relaxation time of the observed lowfrequency dispersion. This relaxation time shows a decrease with increasing pore water electrical conductivity, which is supposed to be associated with a decrease of the electrical double layer thickness. With increasing grain diameter an increased relaxation time is observed, in accordance with theory. Importantly, we find a correlation between the lowfrequency relaxation time and the hydraulic conductivity, which is of high practical relevance.