I always thought watching films that steam in the dark streets was some cool 80s aesthetics. As in 'You are in this dark corner of the city where nobody can hear you' scary or edgy.
I grew up in a city without steam and the sewers would still smoke like that when it got cool out, like early morning; its still fairly warm down there
I thought that too (but more New York Christmas Eve movie impressions) until I saw steam coming from manholes in Denver. Blew my mind that it was a real thing haha.
In addition to the heating/cooling uses, the mint in Denver uses it to clean coins!
Steam rising out of manholes is definitely commonplace in NYC: [1]
There's a stretch of sidewalk in the Financial District that gets so hot that you can feel it walking past on some days. And apparently, sometimes these things explode... [2]
As far as I've heard it's not (all) actual leaks, though, but rather water dripping on the exterior of the hot pipes carrying the steam itself being evaporated.
It's often not the steam pipes leaking. The sewers are very humid and warmer than the air above. As the air convects up it hits the cold air and the humidity condenses. The same thing happens in lots of other cities when the weather is right.
Maybe the steam pipes keeps the sewers warmer in places with steam but they should be well insulated in the end.
you can see it pretty often in NYC, coming up from vents/pipes in the road
i don't think it's steam leaking. it's drainage/sewer water being heated by the steam system (and other heat sources down there) enough that it evaporates and rises up to the street, and then condenses into vapor/fog because the street level is cooler
