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knowledge center: FAQ's

Questions from our steam customers touch on everything operational-from water hammer to wet steam. Browse these pages to learn how steam works and how to make it work for you. If you have more questions, let us know. We'll post the answers.

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Where does Con Edison supply steam?

We supply steam to customers from the southern tip of Manhattan to 96th Street on the west side and 89th Street on the east side.

How do we make steam?

Click here to see an animated presentation of how steam is generated. Click on "Slide Show" then "View Show" to see the animation. (PowerPoint Viewer is needed.)

Why does steam rise out of manhole covers?

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.

What are the orange and white striped "chimneys" that can be seen in the street everywhere in NY City but especially in Midtown Manhattan. What exactly do they do?

The orange and white stacks you see on the streets surrounding a manhole are there for safety - so people don't touch the steam vapor and get burned, since it is hot. The cones also elevate the steam vapor above street level so that drivers can maintain visibility. This steam vapor is caused by water falling on a steam pipe, or a manhole cover or due to a steam leak. If you see steam vapor rising out of a manhole ,and not protected by a stack, (which means we know about it) on a Manhattan street, call us right away at 1-800-75 CONED (1-800-752-6633).

Does steam have chemicals in it? How pure is it?

Con Edison Steam is created from NYC water. The city water is softened using water softeners that are similar to those used in private homes. The softening process adds a trace of salt (regular table salt) to the boiler water but this salt does not evaporate and become part of the steam. Some additional additives are added to the water before it enters the boilers. These additives are all food grade minerals that are approved for this purpose by the FDA and they also remain in the boiler. They do not evaporate and become part of the steam. The steam produced by Con Edison is very pure and is even used by some customers for the sterilization of hospital equipment. Steam may also be used for humidification purposes, for example, in museums, to help protect the art. There is nothing toxic in the steam.

What chemical is used to treat the water for steam generation and what standards does it have to comply with along with the condensate testing schedules and test results?.

Condensate does not have any added chemicals. No chemicals are added directly to the steam and only FDA approved chemicals are added to the boiler water used to produce the steam. The FDA regulation is 21 CFR 173.310 . We do not use any of the chemicals mentioned in paragraph D of that regulation (This paragraph lists chemicals that can only be used if the steam is monitored for their presence. We choose not to use those chemicals at all.)

Condensate can be cooled and used to water some varieties of plants -- specifically plants like evergreens and roses that require an acidic soil. Condensate is naturally acidic (because it tends to absorb carbon dioxide from the air as it cools.) Condensate tends to "wash" the pipe that it travels in and thereby pickup iron. The iron in condensate is not harmful to most plants.

Our Steam is sampled monthly for a detailed and quantitative chemical analyses in accordance with a State regulation 16 NYCRR part 400 and various agreements with the PSC. It is also monitored continuously for conductivity (a global indicator of steam purity) at each point of generation. We have some information about condensate on our Web site

NYC plumbing code permits single wall heat exchangers to be used (as compared to double wall type) if the steam has "a Gosselin rating of 1, including FDA-approved boiler water additives for steam boilers". Does Con Edison's municipal steam satisfy these criteria?

Con Edison is not subject to the referenced NYC plumbing code criteria and has no reason to determine the Gosselin rating of its steam supply in order to maintain the steam quality specifications that do apply. We offer the following information regarding the quality of our steam supply.

Con Edison steam is produced from New York City municipal drinking water. This water is treated using either ion exchange resins (demineralizer or water softener) or membrane technology (reverse osmosis and electro deionization). Chemicals are utilized in these processes to treat the water; however these chemicals are not present in the final treated water product. All of these water treatment processes produce water which is higher in purity than the original source.

The water produced from these water treatment processes is commonly known as treated water. Treated water is utilized in Con Edison's boilers to produce steam. Only Food and Drug Administration ("FDA") approved chemicals are added to the treated water either just before it enters the boiler or while it is in the boiler. The chemical additives that Con Edison utilizes are classified as food grade products and are approved for this purpose by the FDA. These additives that are used in the water that is used to make steam are not distributed into the steam above the limits established by the FDA.

Con Edison's steam complies with FDA regulation 21 CFR 173.310. The steam is sampled monthly for a detailed and quantitative chemical analysis in accordance with a State regulation 16 NYCRR Part 400 as well as other agreements with the New York State Public Service Commission.

How often should customers check their traps?

Manufacturer recommendation: for maximum trap life and steam economy, a regular schedule should be set up for trap testing and preventive maintenance. Trap size, operating pressure, and location determine how frequently traps should be checked. Suggested trap testing frequency is twice a year, at a minimum.

What can cause a trap to fail?

Steam cuts, dirt, or warped discs can cause the trap to fail open. This failure causes a steady stream of steam to be discharged into the condensate header. If a trap is allowed to blow, it can cause the premature failure of other traps discharging into the same condensate line by raising the pressure in the condensate discharge header.

What are some of the signs of a failed trap?

Signs of a failed trap include

  • Cold Trap – trap fails to discharge condensate
  • No condensate or steam coming to trap – plugged strainer, valve closed in line to trap, or pipe line/elbows plugged upstream of trap
  • Worn or defective mechanism
  • Trap body filled with dirt – install strainer or remove dirt/blowdown
  • Trap constantly discharging: trap valve fails to seat, trap too small

Why do my traps sometimes discharge steam?

A steam trap is designed to discharge condensate and trap steam. A very small amount of steam is discharged in the split second that it takes a trap to close after the condensate is discharged, and this is called “blow-by.” Blow-by is unavoidable and lasts only a second. If the trap is continuously blowing steam, it may be worn out, debris may be stuck in the trap, another trap discharging to a common header may be blowing, or the condensate discharge piping may be undersized. If there is excessive pressure in the condensate piping after the traps, the trap may not re-close properly after opening to discharge condensate. You can learn more about traps in the “Best Practices Report” on the Steam Operations Web site, which gives you tips on steam conservation Also, we at Con Edison are available to visit you and provide you with advice/ assistance with these matters. Call us at 1-800- 75-ConEd.

What type of traps does Con Edison use?

Con Edison uses Thermodynamic disc traps. The approved products are:

  • Spirax-Sarco TD52 - Barstock version

Who is responsible for traps before the steam meters?

Con Edison is responsible for all traps before the steam meters. All traps after the steam meters are the responsibility of the building owners. Con Edison provides behind-the-meter services that include steam leak repairs and trap maintenance inspection. For more information click here.

How does steam produce air-conditioning?

Large buildings use machines called chillers to provide the cooling effect. A chiller removes heat from a liquid (typically water). This chilled water is then used to cool and dehumidify the air. Chillers use two methods to cool the water. These are called the vapor compression and absorption refrigeration cycles. Both methods evaporate a refrigerant at a low pressure and condense the refrigerant at a higher pressure.

The vapor compression cycle uses a mechanical compressor to create the pressure difference necessary to circulate the refrigerant. This is the same technology used in home window air-conditioning, except that a steam turbine can replace the electric motor to drive the turbine. With steam, a building will use less electricity during peak periods.

In the second method, the absorption cycle, water is evaporated to provide the cooling and is then absorbed by a salt solution. Steam heat can be used to boil off the water in order to start the cycle again. Besides saving electricity, absorption chillers do not use chemicals that can harm the ozone layer, as the vapor compression method often does.

At what temperature should a steam room be during or after venting?

Steam room temperature should not exceed 100°F.

What is the temperature of steam once it arrives at my house or business?

The steam is saturated steam with an approximate pressure of 165 psig and temperature of 358 degrees F.

Where is the “shut off” valve located?

There are “shut off” valves located in various places throughout the building:

  • Outside street service valve
  • Inside service valve (ISV, first valve in the building),
  • Meter inlet and outlet stop valves
  • Trap inlet and outlet isolation valves
  • Pressure reducing station inlet and outlet stop valves,
  • Steam equipment isolation valves

Which is better-- Flexitallic or Teflon Gaskets?

Teflon gaskets can’t be used when temperatures approach or exceed 500°F. Since there are no areas in the customer premises with temperatures this high, reinforced Teflon gaskets are fine for most applications. Flexitallic gaskets are required for high temperature and high-pressure applications or when the equipment manufacture has specified they be used. In some cases, the flange has been designed with a tongue and groove cut for a specific gasket. Follow the equipment manufacturer’s recommendations.

How often are meters checked for malfunctions in customer buildings?
  • EDP meters are calibrated annually
  • Vortex meters are calibrated every 5 years
  • Shuntflow meters are overhauled every 3 years
Should Con Edison be contacted in the case of a direct replacement job?

Yes. Call 212-683-8830 to schedule steam outages.

Who would support or certify the safe use of a given steam supply in applications where the steam comes in contact with food?

The FDA has a regulation governing the production of steam for food service and Con Edison complies with this regulation. The regulation is CFR 173.310 Boiler water additives. This regulation can be found online at Note that this regulation restricts the additives (to a short list of additives often found in food), which may be used in boilers producing steam. There are some additives listed in the regulation, which may be used as long as their concentration in steam is measured and the steam has no contact with milk. Con Edison does not use any of the additives that have restrictions on their use.

How much does Con Edison charge for repairs?

Please refer to: for steam repair services and prices.

What is condensate?

As steam cools, it changes state from vapor to liquid. This liquid water is called condensate. It is advisable to remove this condensate from steam pipes. Automatic valves called traps remove the condensate and help ensure safety and prevent erosion of pipes and other equipment.

How is condensate removed from the main steam distribution mains and how is it disposed of? Where can I get more information about condensate?

Steam condensate is removed during normal operation by steam traps which are positioned at all the low points on the steam system. The discharge from the traps is routed to cooling chambers and then to the city sewer system. Following an outage, the steam main is drained manually to the manhole environment and if necessary, pumped from that environment using portable submersible pumps. For more information about condensate click on

How can I tell if the operation of my condensate dilution tank is causing me to waste water?

Dilution tanks are instrumented so that condensate temperature regulates the water supply valve. If the condensate return line is carrying very high temperature condensate or steam, this will cause the consumption of city water for dilution purposes to increase. If the condensate is running hot, it may be that your thermal recovery systems are by-passed. It could also mean that you have blowing traps.

What is water hammer?

When condensate is not removed effectively from steam pipes, water hammer can result. It usually causes banging noises in the pipes. The most common type of water hammer is a traveling slug of water that impacts.

What is a “flue”?

A flue is the equivalent to a vent or a chimney.

What should you do when water hammer is suspected and banging is heard?

Shut the steam down and call Con Edison. Our Steam Distribution personnel will provide the necessary assistance.

What causes steam pressure fluctuation?

Steam pressure fluctuation most likely happens when there is a malfunction in the pressure-regulating valve. This should be attended to immediately. Con Edison can supply behind-the-meter support and repair these malfunctions. For more details, click on Maintenance & Services.

What are Behind-the-Meter Services?

Behind-the-meter services include repairs as well as temporary turn off/turn on of steam service. Con Edison provides 24-hour coverage for special services, including replacement of flange gaskets, valve packing, screwed piping, and welding. An inspection will be made and an estimate of the cost of labor and materials provided.

During an outage which valve should be shut down – the inside valve (house) or the street service valve?

The best practice is to close the valve that is connected to the minimum amount of steam piping. This reduces the chances of developing leaks and eliminates corrosion.

Does Con Edison's Steam Operations operate valves after 12:00 midnight?

We have a 24-hour staff, 365 days a year. We schedule our work to minimize customer inconvenience.

How do you know if you have "wet" steam?

Steam is considered "wet" when a small test valve is opened and excessive condensate is seen—especially when an object is placed in front of the valve. We typically deliver steam at a quality of 98% dryness, meaning that there can only be 2% moisture content.

If you have "wet" steam, do you install a blow valve?

No. Traps must be installed at all low points. These traps must be properly sized. If there is sensitive equipment on the line, a steam separator could be required. Call Con Edison to work with you.

Should there be a pressure gauge in the building near the main valve?

There is no code requirement for gauges; however, it is helpful to have a pressure gauge installed on each side of pressure reducing valves. Installing one on the steam station or near the main valve also is a good practice.

Are the pipelines in the street cast iron and how thick are they?

We replaced all of our cast iron pipes and fittings with steel pipes during the 10-year Steam Enhancement Program that was completed in 1999. PIpes rated for 200 pounds per square inch (psig) are schedule 40, or 3/8" thick. Pipes rated for 400 psig are 1/2 " thick.

How much money can be saved when valves are insulated?

Jacket- type insulation products pay for themselves in approximately one year.

What would the conversion factor be to turn mlb usage into Btu’s?

Each pound of steam delivered to a customer contains about 1,200 BTUs. Therefore, an mlb of steam contains 1,200,000 BTUs.

Why doesn’t Con Edison burn natural gas, exclusively?

There are three reasons why natural gas is not the exclusive fuel. Two out of our 6 steam plants have boilers that can only burn oil. While natural gas is currently the less expensive fuel, it has not always been so. There have been times when oil was less expensive than natural gas. And lastly, during the winter season, there are some days when natural gas is in short supply. When natural gas is in short supply, it must be given to Con Edison’s gas customers before any is used in Con Edison’s own facilities. Because Con Edison has the capability to produce steam from two different fuels, Con Edison can reliably produce steam at the best price.

What is considered a large building in terms of steam usage?

We consider customers who use 22,000+ Mlb of steam, large consumers.

Which months are considered Winter months? Summer months?

We refer to November through March as the winter months; our summer months are April through August and the months of August through October are the shoulder months.

What does the underground equipment used to distribute steam in Manhattan look like?

To see a diagram of the underground steam system, click here.

How do I submit my resume?

To apply for employment at Con Edison Company of New York:

What kind of benefits does Con Edison offer?

As a Con Edison employee you will receive a wide-range of benefits designed to provide protection for you and your family and assist you in maintaining greater financial security during your years of employment and after you retire. Here's a list of just some of the benefits we offer:

  • 401K plan
  • medical
  • dental
  • vision
  • insurance
  • pension plan
  • tuition assistance
  • child care and eldercare assistance
  • paid vacations
  • paid holidays

How can I learn more about Con Edison?

Con Edison is a subsidiary of Consolidated Edison, Inc. [NYSE: ED], one of the nation's largest investor-owned energy companies, with approximately $13 billion in annual revenues and $35 billion in assets. The utility provides electric, gas and steam service to more than 3 million customers in New York City and Westchester County, New York.

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