Bacteria growing in your sink drain or hot water heater may cause odor. Naturally occurring hydrogen sulfide in your water supply may also cause this odor. To evaluate the cause, put a small amount of water in a narrow glass, step away from the sink, swirl the water around inside the glass, and smell it. If the water has no odor, the likely problem is bacteria in the sink drain. If the water does have an odor, it could be from your hot water heater. There is an element in your hot water heater designed to protect it from corrosion. Sometimes the element causes sulfide smell as it deteriorates over time. A licensed plumber may be able to evaluate this problem. If you rule out the drain and the water heater, and the odor is definitely coming from the tap water, call KPUD Customer Service at 360-779-7656.