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.

Single Pipe Steam System (Help Needed)

Karl22 Member Posts: 7
Hi all,
Hoping to get some insight as to what may be the issue with our steam heat. In early December we noticed the heat wasn’t warming the house as well as it should. The house is a 1 story cape, 8 single pipe radiators plus 1 radiator on the basement ceiling which is a 2 pipe setup. The main line from the boiler has a T that goes to 3 front radiators & the other side of the T feeds the other 6. I had 2 workers from an HVAC company come out, they replaced the 2 main air vents above the boiler, replaced a clogged pigtail & they added a chemical to the water for rust & scale. They ran the system, main valves hissed by the boiler which I can’t recall the last time they did, felt warmer but of course it was a mild day & couldn’t get a real test. They suggested I replace the radiator air vents & make sure the radiators are shimmed to allow condensation back to the boiler. (2) Vents I cannot get out because they appear they will break off at the threads. I should mention the boiler is about 40 years old, & runs off a millivolt supply; here is the current status: Steam gets to the radiators with new vents, especially the 3 closest radiators but none of them radiate heat away from the radiators & quickly cool down. Even the basement doesn’t feel warm & the pipes are not well insulated. The others are getting steam but only across the top (about 35%) then the rest either mildly warm or cold. Even tilted, I can loosen (not remove) the valve/radiator nut & have water drip out. This helps but the next day it’s the same results. I’m at a loss what’s going on, I called a company first before getting the 2 workers here, both without assessing the situation were wanting to sell a new boiler, I’m hoping that isn’t the case, any ideas are greatly appreciated.


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578
    We discourage any additives from being put into steam boilers, as it will sometimes produce unsteady boiling.
    As your problems predate the additive, I would suggest draining out the water to remove the additive, perhaps several times, until the water in the sight glass is clear.
    I would not suspect the radiator vents so much as the main vents. What type are they? Check and see whether any air is coming out of them, at the start of the heating cycle.
    I am glad they at least cleaned out the pigtail, so the pressuretrol can properly sense the pressure.
    Can you post pictures of the settings on the pressuretrol, and the piping on the boiler, so we can see what may be wrong here. Hopefully, they did not raise up the pressure settings in a misguided attempt to force more steam into the radiators!
    My guess is that the pigtail had become clogged, allowing higher pressure to interfere with the operation of the vents; however the additive has caused an unsteady water line, and bad boiling, interfering with the production of good dry steam. Have you had to add much water to it lately?—NBC
  • Karl22
    Karl22 Member Posts: 7
    Thanks NBC for your fast reply, i will get pics on Sunday & upload them. The main vents are Gorton & rad vents are Varivalve. Haven't needed to add much water, probably what i typically added. I agree cleaner to the water is not a preferred method, however they told me this after it was done. I think the pigtail is getting clogged again, the boiler is running at 1/2 lb but i will double check all settings. Definitely there is no hissing at the main vents as there was the day they were changed.
    Thanks again, Karl
  • newagedawn
    newagedawn Member Posts: 586
    its all in the vents, and a fresh skimming couldnt hurt
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • BobC
    BobC Member Posts: 5,479
    Generally you want to vent the steam mains very fast and the radiators slowly. If you are using HeatTimer VariValves that could be a problem because they are very fast vents and very hard to adjust at the low end of the scale.

    Could you sketch a simple diagram of the steam main that shows approximate length and diameter of each leg of the main. Also show the location of the main vents and the radiator pipe takeoffs. Indicate which radiators have problems heating.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Mike Cascio
    Mike Cascio Member Posts: 143
    Thosr radistor vents are TOO FAST steam will go across the top of the radiator and close the vent while leaving most of the radiators filled with air.
    You need one of the following vents,'

    If the radiators are around the same size
    Hoffman 40
    Ventrite 11
    Gorton 5
    If you desire sone fine tuning adjustment
    Dole 1A
    Ventrite 1
  • gerry gill
    gerry gill Member Posts: 3,078
    varivalves are not very reliable on one pipe steam as they can skin over with water then they seem to stop venting. Least thats been my experience. They work much better as mini main vents.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • Karl22
    Karl22 Member Posts: 7
    Thanks for all the info posted, the radiator vents are the heat timer varivalves. I was told that since they are adjustable i had better control on how fast the steam would enter the radiator. I'm guessing the trapped condensation is from the vents closing & no venting to allow it to return immediately to the boiler?
    The Gorton main vents are new & they made a hissing sound the 1st day but not anymore. I did a birds-eye view of the heating system, hopefully that will be of some help. The kitchen & bedroom #2 have old air vents that will break if i attempt to remove them. Again, all help is appreciated.