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.

Leaking Steam Radiator Valves - Single Pipe System

First time posting. Learned a lot from the site and thanks to all, especially Dan Holohan. I bought three of his books and poured over all of them.

I bought a 110 year old house with a single pipe steam system with a 40 year old Weil McLain boiler. Been going down a path of tightening up the system, as I've been adding make-up water. Flooded the boiler with about 1.7 psig on a new 0 to 5 psig gauge and took the top off the boiler. Left it sit for two hours and not leaks, not a drop. I've got a few radiators that are wet/damp on the bottom, but it's not accounting for the 10 gallons a month of make-up. The 10 gallons is an estimate....

So I decided to start looking a little harder. Except for a small drip on the header during start-up, I dont see any drips from the steam or condensate piping, as 98% of the pipes are exposed. I would expect i would see gallons of condensate dripping from one section of steam piping above the ceiling. I'm thinking, more than likely, the steam leaves the valve or radiators like a fart in the wind. Mind you, I dont hear or see steam leaving the radiators or valves. I tried the mirror trick and that doesnt work. All rad vents are new and there's no spitting. Some of the new Maid-O-Mist vents fill with water, but that's story for another posting.

So I pressure tested the system with about 1-lb of air and applied a soapy solution around the valves. Found many of the valve stems leaking. I also used the same soapy solution while the system was heating up and found a few couplings leaking. Some of the leaking valves, look original at 110 years old, others maybe 20 years old. I could repack the stems, but it's not going to fix the couplings and would like to fix them once or least while I own the house.

There seems to be a few manufactures of single pipe steam radiators valves which include Marsh, Legend and Bluefin. Marsh is manufactured domestically in Illinois. Legend in sourced overseas and I would assume Bluefin too.

Besides the comment, "you get what you pay for", is there a valve that's better than the other? I'm wondering if the premium price for the Marsh valve is worth it. The Marsh valve is a packless stem, so maybe it's not going to leak?

So wondering if anyone has recommendations, Marsh, Legend or Bluefin? Thanks in advance!


  • Jamie Hall
    Jamie Hall Member Posts: 23,271
    edited January 2021
    On the leaking radiator valves -- save yourself a lot of trouble and see if you can remedy the leaks by simply tightening the packing nuts, or if that doesn't work repacking them. One pipe steam radiator valves -- with very very few exceptions -- use standard thread type packing, and it's a lot easier to repack than to replace!

    On the leaks -- do not discount a leak because it is only a little drip. A little drip, say as little as once a minute, will be a quart per day -- or around 7 gallons a month right there.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • WilliCT
    WilliCT Member Posts: 3
    Jamie, thanks for the response. I'll look into repacking the stems first. Def saving myself the trouble.

    The drip from the steam header only occurs when the boiler starts to make steam, maybe a 3" spot on the concrete, then it dries up. The fitting is covered in asbestos so i can't see what it's doing when hot. Could the fitting be leaking only when heating up or when it heats up it evaporates off the pipe and gone forever.
  • Jamie Hall
    Jamie Hall Member Posts: 23,271
    When it heats up it evaporates -- unless the leak is a rather unusual one which closes when heated up.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England