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Working vents don't close
Homeowner with a one pipe steam system hoping someone can have suggestions. I have a vaporstat and running around 1/2PSI and have working main vents in the basement. My house has convectors on the 1st floor and cast iron radiators on the second floor. All radiators are pitched back to the pipe and heat up fast. All of my vents close as soon as steam reaches them, but one of the radiators (my largest one) has a problem closing the vent for some reason. I used 2 new Hoffmans and tried a Gorton from another working radiator. I also tried Maid-o-mist with various flow rates and currently using Varivalve. With the Gorton, the valve just does not close at all, it lets the steam out and makes steam noise when it reaches it. With the hoffman, it makes noise for a minute and finally closes. Varivalves seem to work best but still spit out some water for a few seconds before closing. I have this radiator pitched down to the pipe and thought that the pitch is too high for a float type vent thinking that the float needs to be more level, but removing the pitch and bringing the radiator to the floor did not fix anything. The rest of the system work great with vents closing on time with no noise, so I'm at a loss. Any ideas?