Handwashing is one of the vital public health measures to prevent COVID-19 pandemic from spread. However, water loss from excessive handwashing may put enormous pressure on the already overstretched groundwater resources and households’ economic well-being. Therefore, this study aimed to determine the water loss during handwashing amid the COVID-19 pandemic with an emphasis on the waste of groundwater from essential hygiene activities at domestic scale. Sociodemographic data were collected using a web-based survey tool among 1980 participants and an experiment was conducted among 126 voluntarily interested participants to estimate the amount of water wasted during handwashing. A total of 80% of the participants washed their hands regularly after returning home from outside. About 57.27% participants generally did not turn off their tap when washing their hands. A single participant, who keeps his tap on throughout the handwashing process, wasted approximately 1.7 L of water per handwash and 14.9 L of water per day. Handwashing when a tap is on, raised the water loss at 13-fold during this pandemic compared to the non-pandemic situation which cost extra 224.95 BDT (2.65$) per day for 1980 participants. A large number (57.27%) of people keep their faucet on during lathering hands with soap and scrubbing, thus wasting a considerable amount of water (1179% more compared to pre COVID-19 situation). The loss of water during handwashing is an alarming but less attentional issue. Behavioral change interventions are needed to aware people to shut off the faucet at periods when water is not being used.