Why does steam come out of manhole covers in some cities?
Question #101526. Asked by whee.
Schoonie101
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Schoonie101 18 year member
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Why does steam rise out of manhole covers?
Steam can come from manholes for several different reasons. The most common is water infiltration into the manhole. Water comes in contact with the hot steam main and causes vapor. Another source is leaks, either within the manhole or on buried piping between manholes. There is no "natural" venting process.
http://www.coned.com/steam/kc_faqs.asp#two