The Granular Matrix Sensor (GMS) is an indirect method for soil suction measurement. Since GMS is comparatively inexpensive, robust and usually provide continuous soil suction data, it is a natural candidate for civil engineering practice. The sensor has been used mainly for irrigation purposes, and also for some civil engineering activities. Questions about its effectiveness and reliability are still posed, making studies about this topic desirable. This study presents a laboratory comparison between Watermark and an ordinary tensiometer during an equilibrium period and for a wetting procedure performed in a compacted sandy silt soil (residual soil of gneiss). The results yielded that GMS may provide tensiometer equivalent suction values in a context of no significant water content variation. However, it takes a longer time to obtain stabilized suction values. During the wetting procedure, GMS presented a delay of about 2 h in detecting water while tensiometer detection was almost instantaneous.