I have a one-pipe steam radiator system. Recently one of the radiators started hissing so I replaced the vent. Now I get an occasional loud blaring noise lasting a couple of minutes once a day.

The old vent was a Maid-O-Mist #4, and I replaced it with a HeatTimer VariValve. I pushed the slider all the way to "closed" since I thought this would match the old vent's venting rate the closest (the boiler's in the basement, this radiator is on the first floor, first in the pipe line).

The vent is nice and quiet most of the time. But in the morning, after the boiler has been going through several firing cycles, the noise starts. The first time it woke us up and scared the hell out of us—as if there were some alarm going off. When I inspected the radiator, I couldn't find any steam or air gushing out with enough force to cause this level of noise. After about two minutes the sound lowers in pitch and eventually peters out.

I've lived in this house for 15 years and thought I heard all the sounds a radiator could make, but this one is new to me. I've tried tightening the vent an extra turn, thinking maybe steam was escaping out of the hole. Should I open it up a little more?

1 Answer 1


GIven it's the only adjustment the thing has, and you set it all the way closed, opening it somewhat seems the obvious thing to try...

  • Yes, I'll try that next and report back. I was also just wondering if anybody had experienced this noise before, and if they did, what had fixed it. Commented Nov 6, 2023 at 14:20
  • So far, opening the vent more hasn't helped. Commented Nov 7, 2023 at 23:51
  • Update: opened the vent a little more than halfway and now the blare is a whoosh. I think I'm making progress! Commented Nov 8, 2023 at 13:09

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