Accurate temperature measurements in flow lines are critical for many industrial processes. It is normally more a rule than an exception in such applications to obtain water flows with in-homogenous temperature distributions. In this paper a number of comparisons between different Pt-100 configurations used to measure the average temperature of water flows with in-homogenous temperature distributions were studied. By using a custom-built flow injector a water flow with a hot water layer on top of a cold water layer was created. The temperature difference between the two layers was up to 32K. The average temperature from a custom-built multiple Pt-100 sensors (consisting of 9 Pt-100) was used as reference. Our study shows that for a 32 K temperature difference between the two layers the deviation to the references decreased from about 4 K to 1 K by taking the average temperature of 4 Pt-100 mounted in the same pipe plane (90° apart) instead of a single Pt-100. Overall the deviation to the temperature reference for the average temperature of 4 Pt-100 is remarkable lower than the deviation for a single Pt-100 under the same conditions. In addition the immersion depth of a single Pt-100 was also investigated at three different water temperatures.