Water Heaters - Hydrogen Gas

Hydrogen gas can be produced in a hot water system served by water heaters that have not been used for a long period of time (generally two weeks or more). 

HYDROGEN GAS IS EXTREMELY FLAMMABLE!! 

To dissipate such gas and to reduce risk of injury, it is recommended that the hot water faucet be opened for several minutes at the kitchen sink before using any electrical appliance connected to the hot water system. If hydrogen is present, there will be an unusual sound such as air escaping through the pipe as the water begins to flow. Do not smoke or use an open flame near the faucet at the time it is open.