New vents still won't stop hissing

Doug T

I have a single pipe steam system with 9 radiators. All of the vents, with one exception, have been hissing very loudly once the cold weather came on strong. This loud hissing comes after the normal hiss of the air escaping, and the radiator has heated up. Placing a finger by the vent hole quickly confirms that steam is escaping. The hissing is not a "clean" hissing, sounding more like a buzzing/sizzling, and loud enough to wake us up at night.

I have come to discover that that the boiler was running at too high pressure, and have since turned it down. The hissing continued, but maybe didn't sound quite as "angry". Hoping that it was just the higher pressure that was responsible for mucking up the vents, I bought two cheapo vents just to see what would happen. These new vents continued to vent steam from day 1, the only difference being that the hiss sounded somewhat "cleaner", but still quite loud.

What should my next course of action be? I have asked a plumber and the gas company tech about this, but they seemd to be at a loss. Please note that there are no vents on the mains. Also note that I am new to this but have been trying my best to get at least a basic level of understanding.

Many thanks for any help.

Dale

No vents on the mains

I guess the problem is that the little rad vents are trying to vent all the air. Look to see if there were main vents that have been removed. Carefully check the pitch of the pipes ( insulated of course) back to the boiler. If you find plugged openings at the main ends, often next to and above the boiler remove the plugs and temporarily put it simple 1/2 in ball valves left open when the boiler starts steaming. Close the valves when steam comes out and then go up stairs to check the rad vents.

Mark Hunt

You could


also have a carry over problem. The "buzzing" noise could be condensate in the air vent.

Main venting would be a very good idea since it would relieve those poor little pepper shakers of the awsome duty of venting the entire system.

Any chance we could see a pic of the boiler piping?

Mark H

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Doug T

I will probably have someone in to install main vents, as that certainly seems like it would benefit the system. And while I see how that lack of main vents and the extra pressure that creates at the rad vents would gunk up the rad vents over time, does it make sense that this would happen to brand new vents, preventing them from closing?

I will work on getting some pictures up so you can have a look at the ancient beast.

Mark - could you please explain a carry-over problem a bit more. I will say that once in a while, but certainly not often, I will see a spittle of water come out of the vents.