Why does steam rise from manholes in Denver?

In Re: Why does steam rise from manholes in the U.S.? a shout-out to Denver, CO. Although NYC/Con Ed is the largest such system, Denver has the oldest continuously operating commercial district heating system in the world.

So unanswered in the reply:

  • Why no steam power in European cities?
  • Why does the steam not stay in the pipes and escape through manholes?

For the same reason your roof might leak. Also, from water on, rather than in the pipes.


Planting 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

Those are steam pipes in tunnels (SF has them too), not steam from sewers.
“Steam” (vapor) exudes from our sewer system often, usually in the cool mornings from everyone’s hot wash water flowing to (hopefully) the treatment plant.

Chase Field, where the Diamondbacks play, is cooled baseball season with a chilled water system. Non-game days the excess water is is sent to adjoining businesses. We got all the heat we can use already.

There is still district heating in some parts of Europe (I’ll try to find an example).

I notice that Denver originally provided steam power for elevators. Melbourne and Chicago provided hydraulic power (high pressure water). They may have been competing technologies.

All that steam is presumably manufactured in the steam factories that always feature so prominently in the climactic fight scenes in the movies. Those factories also make the crates for FPS video games.

About ten years ago I was involved in a proposal to develop some electronics for a new generation of heat meters for district heating applications for a German company. Heat meters measure energy consumption by customers connected to a central hot water heat plant. Heat meters consist of a flow meter (which measures the volume of hot water passing into a customer’s premises) and the temperature difference between the water entering and the water leaving. From these measurements the energy used by that customer can be calculated (and billed).

Since this (large multi-national) company was embarking on a very expensive development effort for a more reliable heat meter (current meters are electro-mechanical, they were developing an ultrasonic flow meter) with remote communication of usage information, I would infer that district heating is quite common in Europe.

Those factories are, of course, wholly-owned subsidiaries of the Acme Corporation.

Iceland is considered European in various ways and has a lot of geothermal steam distribution. 85% of households get geothermal steam heat. I’d provide a link, but this seems even better.

Just spent a copule of days in St Louis MO, and noticed that “Trigen St Louis Energy Corp” is still providing District Heating – there are manhole covers marked “Steam” scattered around the CBD. I think perhaps that the steem is coming from the wonderful “Union Lighting and Power Company” building down by the river, which still has a very faint smell of coal, but not enough to indicate that it is currently burning coal.

Trigen redirects to “Veolia North America”, which lists the following district heating assets:

Philadelphia, PA
Boston-Cambridge, MA
Baltimore, MD
Kansas City, MO

More importantly, they also manufacture flaming barrels. Waste heat from the barrels is used for steam generation, making it a very efficient process.

The air in tunnels under the surface changes temperature and humidity, slower than above the surface.

If the difference in temperature and humidity is right. Then tunnel air will rise and condense into visible vapor. It can happen anywhere, if conditions are right. Leakage of heat and water in the tunnels can make it happen more.