Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

No apparent main vents

61356 Member Posts: 1
Last spring I had my boiler replaced by a very competent steam fitter who unfortunately

passed away in the fall. When I started heating this season some of my radiators began to fill with water and leak at the relief valves. Since then I have replaced a 1" sagging return pipe (laying in the dirt in an elevated crawlspace) with a 1 1/2"

new pipe. In the process the technician failed to replace what i believe to be the only

main vent in the system which was attached to the old pipe. I also replace all 11 veri-vent radiator vents with new conical ones and the leaking has stopped.

I noticed that the cut-in is set at 5.5 psi and from reading Dan's book plan to dial that back to .5 as well as check the diff setting inside.

My question is, will the air manage to escape through the radiator vents with no main vent? The steam has been getting to all of the radiators with the higher pressure and there has been very little noise but the system cycle time is 45 min to an hour and the radiators cool completely prior to the call for more heat.

I have a new tenant moving into the house and would like this system to be as efficient as possible but at the same time don't want to chance screwing up something that appears to be working.

Thank you for any advice.


  • Double D
    Double D Member Posts: 442
    edited March 2014
    You need to vent the mains

    Can you post pictures of the boiler and the near boiler piping? Also post pictures of piping and end of mains. Someone here should be able to help you with where to place them.
  • Jamie Hall
    Jamie Hall Member Posts: 23,276
    You do need main vents

    as they will make the efficiency much better -- and won't mess up anything.

    You may also need to replace the radiator vents.  If you have really been running at 5.5 psi, some or all of them may have died.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England