Problem with whistling steam vents (and other stuff...)

Phil McTimoney

I've just moved into a house that has steam heat. This is my first experience with steam and although I'm learning, some things still have me puzzled. Sorry if this has been discussed a thousand times already...

There is an addition on the back of the house with two new roooms - a kitchen extension and a bedroom above it. The radiator in the kitchen only gets hot half way across and doesn't really heat that area very well (problem 1). The radiator above it gets tremendously hot very quickly and whistles like crazy (problem 2). I've replaced the steam vents on both radiators with new vents from Home Depot (they are 1/8th inch, with a twistable thing on the top to adjust the size of the vent).

In general, the other radiator vents (in the original part of the house) gurgle and whistle a bit (but not as much as that bedroom). Can this be cured by cleaning or replacing the vents?

Finally, what is a mains vent, how do I look for it, and how do I decide it it is the correct side. From reading this site, I saw a suggestion that the whistling could be caused by an incorrectly size main vent. But I don't know where to take it from there.

Thanks for reading this!

ed wallace

whistling vents

your best bet would be to click onto find a contractor and see if there is anybody near you who understands steam heat the other thing is click on to books and more buy a copy of the lost art of steam heat good luck

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David Efflandt

Maybe pressure is too high

Speaking as a new homeowner myself, read everything about steam and boilers in the "Steam Problems" and "Hot Tech Topics" here.

When asking questions, you should state whether it is 1-pipe or 2-pipe steam (is there just 1 pipe to each radiator?).

Noisy/inadequate air venting might be due to too much pressure. A residential steam system should typically operate 0.5-1.5 psi (check Pressuretrol setting). Higher pressure makes steam move slower and can cause air vents to make more noise and close too soon (adjustable vents typically close if pressure rises above 1.5 psi). Vents with fixed orifice can vent to higher pressure, but should be properly sized.

If both radiators in question are on the same steam line, reducing the venting of the one that heats up first may allow the other one to vent faster. But you may need a larger air vent with fixed orifice for one that heats slower than all others.

Look for main vents near (not at) the ends of steam mains in basement. My small 1-pipe system has no main vents, so air vents on distant radiators are larger than normal, but vent quietly and everything is balanced.

David Efflandt

Maybe pressure is too high

Speaking as a new homeowner myself, read everything about steam and boilers in the "Steam Problems" and "Hot Tech Topics" here.

When asking questions, you should state whether it is 1-pipe or 2-pipe steam (is there just 1 pipe to each radiator?).

Noisy/inadequate air venting might be due to too much pressure. A residential steam system should typically operate 0.5-1.5 psi (check Pressuretrol setting). Higher pressure makes steam move slower and can cause air vents to make more noise and close too soon (adjustable vents typically close if pressure rises above 1.5 psi). Vents with fixed orifice can vent to higher pressure, but should be properly sized.

If both radiators in question are on the same steam line, reducing the venting of the one that heats up first may allow the other one to vent faster. But you may need a larger air vent with fixed orifice for one that heats slower than all others.

Look for main vents near (not at) the ends of steam mains in basement. My small 1-pipe system has no main vents, so air vents on distant radiators are largest size available ("D"), but vent quietly and everything is balanced.