Main steam vent spitting water

Nomas

Hi, I have a 90 year old house with steam heat, 2-pipe.  The main vent in the basement is spewing water during the heating cycle.  I replaced the vent with no luck, it is still spitting.  From reading various threads I checked the water level in the boiler and it was completely full (above the site glass).  I have drained the system and allowed the boiler to refill itself and the water is now sitting at the right level in the sight glass.  I went looking at the radiators and noticed that two of them have steam vents on them, above the return line and the others have no vents or steam traps (examples of each are attached).  From my research it seems like the vents should not be there but should there be steam traps or is there some other mechanism internal to the radiator that needs to be checked?  Also, is it worth replacing valves? I have not touched the valves so I am not sure what condition they are in.  Thanks in advance.  

Jamie Hall

Pictures didn't attach...

If it is two pipe (supply and return), unless it is VERY old, there needs to be a trap on each return or, just possibly, a control orifice in the supply valve. No vent on the radiator. On the other hand if it is one pipe -- just the supply -- then you do need a vent on the radiator. And it is possible to have both kinds on one system, though it's not common.

Nomas

Thank you, here are the pictures.  So the vent should not be there? I read elsewhere that the vents are sometimes used (incorrectly) to mask another problem with draining.  On this style radiator would I need to install steam traps since there are none that I can see?  

Jamie Hall

Hmm... well, there should be some means to prevent steam from getting into the return line. The vent will do no harm. Then the system is running and those convectors are nice and hot, can you check in the basement where the return from the radiator meets a main return? It should be warm -- but not steam hot.