Hydrogen and water heaters

[MasterPlumbersKeymaster]

This web site: http://safetycenter.navy.mil/publications/ashore/AshoreWinter99HTM/dishwasher.htm

has a story about hydrogen being generated in homes. It has a story about a dishwasher that allegedly exploded from hydrogen build-up. It says: “under certain conditions, hydrogen gas may be produced in a hotwater system that has not been used for two weeks or more. If the hot-water system has not been used for such a period, before using the dishwasher, turn on all hot-water faucets and let the water flow.”

Is this accurate? Or is this an urban legend? How does water produce hydrogen gas in a home water system?

[GuestParticipant]

The process of electrolysis, creating current between dissimilar metals separates hydrogen from oxygen in water. Chlorine can separate from bleach used to purify water leaving hydrogen. These are small amounts and separation is infrequent, but they can occur, so manufacturers have to warn of the possibility.

[GaryPurolite1Participant]

Yes, it is accurate. Hydrogen gas can build in a water heater as the article explain. I have not seen it happen but it makes perfect sense.

[SylvanLMPParticipant]

Hi Harold YES it is very possible with the proper acidic water conditions

When I took up ASME training for unfired pressure vessel and low pressure boiler inspector we saw several videos of hot water heaters exploding because of the air space created by the hydrogen in very low pH conditions with an electrical potential across the system, BUT hydrogen is the lightest gas and thus vents quite easily, so I would be more concerned about stumblebums dabbling in heating without any formal training causin explosions.

Hydrogen flame is great for melting Quartz glass and as an apprentice we used hydrogen flame combined with oxygen for making our own beads for acid waste piping systems.

Accidents can occur BUT there must have been other chemicals present in the dishewasher to have caused this type of explosion.

[Author]

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