The core part of the internet of things (IoT) is the wireless sensor network (WSN). WSN makes sensor-based devices communicate without any human action. In recent years, WSN and IoT technologies have transformed the environmental monitoring field. Water quality monitoring is one of the main environmental monitoring application. The communication unit is the main energy-consuming part of WSN. Since most of the WSN is powered by a battery, low power communication is very essential. So the main challenges in water quality monitoring applications are low power and wide communication coverage. This paper provides a critical review of various communication technologies used in water quality monitoring system. The communication technologies are ZigBee, Wi-Fi and newly emerging low power wireless technologies like LoRa, Sigfox and NB-IoT. The comparison of these technologies by considering different factors is also provided.