I am having an issue with a single cast iron radiator where it is not heating up at all. All other radiators are working fine in the apartment. A lot of people suggest bleeding the radiator, however, I can't seem to find any bleeder valve on this kind of cast iron radiator. I have attached a few pictures. Is there any other way I can bleed this radiator of the air that is inside it? I have already replaced the air vent valve but that didn't seem to help with anything. Thank you!





3 Answers 3


The heating system is what is called a "1" pipe heating system. It is not a hot water system therefore the radiator does not require bleeding. I can not see the make or model number of the vent on the radiator so I can't comment on whether it the correct type. Also make sure that the inlet valve on the left side is fully open and not partially closed. Be careful when replacing the vent on that radiator or any of the radiators when the boiler is firing, steam can come out a cause very bad burns. Is this a single family home or an apartment? If it is an apartment call the building manager and have them replace the vent. If it a single family home make sure that you turn the boiler off before working on any part of the system.

  • This is a 2 family home where the same type of radiators is in the same position on the 1st floor. Since I own the building I was trying to see whether I can diagnose before reaching out to a plumber. I have confirmed the inlet valve on the left is fully open.Wondering if this valve is what is causing the issue. Going to see if the pipe underneath the valve gets hot at all. Dec 27, 2017 at 18:54

Steam systems have a simple method of operation. Steam is generated in the boiler. The steam being hot rises and fills the radiator. The steam cools,condenses back to water and gravity flows back to the boiler. The vent valve serves two purposes, let the air out and keep the steam in. If the radiator doesn't get warm either the steam isn't reaching the radiator or the air is not escaping allowing the steam to enter. Feel the pipe before and after the shut off valve. Hot on one side and cool on the other the valve is closed or clogged. The vent appears adjustable. By rotating the cover with the small screw in it you can adjust the rate that the air escapes. The radiator also should be slightly angled with the vent side slightly higher than the inlet valve. Another possibility is the radiator vents are not balanced. They should be adjusted so that the radiator closest to the thermostat doesn't get so hot that the thermostat shuts down the boiler before the radiators farthest away get hot.

  • Thanks for the great idea. I am going to check the pipe before and after the inlet valve. This is something I did not think of earlier. If the valve is clogged I'll have to contact someone to get it looked at. Thanks for the immediate response. I'll keep you posted! Dec 27, 2017 at 18:56

As stated above this in not a hot water system. It is a steam system. For safety sake KIM the steam is always above 212*. It is very hot and can burn quickly. This being said I recommend the following: First make sure the inlet valve is in the on position. Top left to open. Check for any change of operation in this radiator. Then turn the system off long enough to allow the radiators to cool and the house temperature to drop a few degrees. Carefully remove the vent valve on the side of the radiator. (The system operates under very low pressure. When the system is cool, there is no pressure in the system. Upon start-up of the system, several minutes will be required to see any evident pressure in this radiator.) Turn up the thermostat. Stand guard at the radiator. If things are working properly, before long you will be able to see, hear and feel air being pushed out of the radiator to make room for the steam. In the beginning it will be at a very safe temperature. If you start to feel air being expelled you know that there are no blocks between the radiator and the boiler. Allow the system to continue to run for a couple of minutes. At a safe distance, observe the radiator vent hole. You should, before too long, see actual steam being expelled from the radiator. The radiator will be heating by now and the steam expelled will be hot. Turn the system off. Purchase a new replacement vent. Any number of on-line vendors will be happy to send you one.

If on the other hand nothing happens with this radiator, you probably have a inlet valve problem. Disconnect the radiator and move it to one side. (Be careful, it is very heavy, it is top heavy and it has a narrow base.) Remove the inlet valve. Preform the same test listed above. If you get steam, purchase and install a new replacement inlet valve. Reconnect all the piping with new valve. Radiator should work as designed.

The vent valves are designed to be adjustable. It the room heats too quickly, close the vent valve a bit. If not quickly enough in relation to the rest of the house, open it a bit. If it really lags behind, you may have to close the others in the house a bit to give this radiator higher priority.

  • I'm glad you said something about the steam being so hot. I am also leaning toward there being an inlet valve problem. I'm going to check the piping this afternoon to see whether the piping connected to the inlet is getting hot at all. It's possible I might have to shut off all the other radiators in order to kick start this one. Going to see what I come up with this afternoon. Thank you for the response! Dec 27, 2017 at 18:59
  • If the branch that this heater is on is totally blocked, bad vent and or bad inlet valve, this pipe will not get hot because the air in the line won't allow the steam to go this way. No steam, no heat.
    – Paul Logan
    Dec 28, 2017 at 21:01

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