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I have one-pipe steam radiators in a home built in 1905 (condoized in 1998). Only one of the radiators, the largest, makes this awful rattling sound when the system heats up:

https://youtu.be/IHJjEDvBcLc

I’ve read about the typical sounds to expect from a steam radiator: hissing from the air vents, potential banging or clanging from trapped condensed steam (which can often be remedied by tilting the radiator toward the valve using shims). But this rattling seems unusual, and only one of my five radiators does it.

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The disc or the cage inside the valve (depends on the mfg of the valve), is loose or has become unconnected from the valve stem. 1st, try to turn the valve all the way open (CCW). Remember, on a 1 pipe steam system the radiator valves can only be fully open or fully closed., no half open. If this does not quiet the valve you will have to remove the top of the valve and remove the disc or cage assembly that opens/closes the valve. I would have someone qualified in plumbing do this. Yes, with this old piping, you can break fittings and the piping, so I would wait till summer and contact the owner of the property if it is not you, and the building manager.

If the plumber knows what he is doing the fix should go OK. Anytime I fixed a valve like this, I used a back-up pipe wrench on the pipe to lessen the torque on the pipe. You hold the pipe wrench any way you can and tap the wrench on the top of the valve with a 3-4# hammer to snap the bonnet loose. Worked every time. One more thing, if you want some temperature control on rooms that overheat, you can add 1 pipe steam zone control valves to that radiator. They work by controlling the venting of the radiator. If you do this, the thermostat controlling the boiler should be moved to the coldest room and that room does not get a radiator control. Do a search at Supplyhouse.com or Danfoss.com. I like supplyhouse the best for their information. Let me know if you desire more info. There may be newer products but I have been retired for 11+ years. hope this helps.

answe

  • Thanks so much. I'm the owner. I'd rather not wait until summer to have this fixed. If I call a plumber familiar with steam systems (I'm in Boston, USA, where these systems are still common), do you think I'd risk facing a major problem & going without heat? Is the worst scenario the valve breaks, or is there a risk the riser pipe also breaks while trying to remove the disc/cage? – symplectomorphic Jan 3 at 19:47
  • If the plumber knows what he is doing the fix should go OK. Anytime I fixed a valve like this, I used a back-up pipe wrench on the pipe to lessen the torque on the pipe. You hold the pipe wrench any way you can and tap the wrench on the top of the valve with a 3-4# hammer to snap the bonnet loose. Worked every time. One more thing, if you want some temperature control on rooms that overheat, you can add 1 pipe steam zone control valves to that radiator. They work by controlling the venting of the radiator. If you do this, the thermostat controlling the boiler should be moved to the coldest roo – d.george Jan 4 at 11:58

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