[Superman]

I'd check the hose connections. Usually, two somewhat flexible lines run to your heater. The connections are like garden hose connections. So.....there are a total of four screw connections. I'd turn off the power to the heater, turn off the water, relieve the pressure, then disconnect those hoses. I might use a teensy bit of silicon grease on the mating surfaces, then reattach them. Snugly.