Small vented point of use water heaters are a popular means of providing hot water to a single sink or basin in homes, kitchens, workshops, surgeries and similar environments.
These products are variously known as 'Open outlet', 'Displacement' or 'Non-pressure' water heaters. They have an open outlet and rely on the opening of a tap or valve on the inlet side to displace the hot water in the heater with incoming cold water.
During the warm-up cycle it is normal for expanded water to drip from the spout or tap.