Hydrogen gas build-up in dormant water heaters

Ran accross this in State Industries manual…

HYDROGEN GAS: Hydrogen gas can be produced in a hot water
system that has not been used for a long period of time (generally
two weeks or more). Hydrogen gas is extremely flammable and
explosive. To prevent the possibility of injury under these conditions,
we recommend the hot water faucet be opened for several
minutes at the kitchen sink before any electrical appliances which
are connected to the hot water system are used (such as a dishwasher
or washing machine). If hydrogen gas is present, there will
probably be an unusual sound similar to air escaping through the
pipe as the hot water faucet is opened. There must be no smoking
or open flame near the faucet at the time it is open.


I’m not sure what they may be refering to but it may be the result of a bad anode rod in the water heater. Some of these can give off gas that will cause bubbles to come out of faucets. This problem is usally only found with systems on wells. Though I have had to change a few on city water. They can be replaced with a different materail to prevent this or removed all together. Removing them completey will void the manufactures warrentee. Also, a rotten egg smell can also be caused by the anode rod.


Had this discussion at yesterdays inspection. The seller brought it up that there was a warning about this situation in the operating instructions of her washing machine. She seemed to be quite worried about it and wanted to warn the buyer. I have never heard of any appliances blowing up, has any one else?:shock: