We recently moved in to a 1934 home with steam radiators.

Our upstairs bedrooms are cold compared to the first floor. A room adjacent to our kitchen is generally warmer than the rest of the house.

Can I adjust the radiators to try and correct this imbalance? It is possible the prior owners were ok with the bedrooms being cool because they were empty nesters. We are home all day due to covid and would like the rooms to be the same temperature.

I have attached a picture of a standard radiator in our house. Most of them had Hoffman adjustable valves. On the first floor the valves are set to 2 or 3 and upstairs they are 6/open.

I am confused if 6 translates to "hotter" than 2, if it's an inverse relationship or direct relationship.

I don't want to start fiddling if it will upset the apple Kart. Would anybody know if I should open the valves on the first floor and close them on the 2nd floor? I am assuming that opening or closing the input valve is wrong to moderate the heat and that the proper adjustment is through the air valve.

Any thoughts would be appreciated.

enter image description here

  • Can you tell if the radiators have a vent on them with only one pipe connecting them to the system, or do they have two pipes connecting them to the steam system? That's the big question here...throttling one-pipe systems in particular doesn't work as folks think it does Jan 30, 2021 at 1:57
  • @ThreePhaseEel Count the pipes on the radiator in the picture ;^)
    – Ecnerwal
    Jan 30, 2021 at 3:18
  • @Ecnerwal -- I was suspecting 1-pipe based on the pic, but couldn't tell for sure Jan 30, 2021 at 3:25

4 Answers 4


I've not lived with a steam system, though I have some understanding of them.

Air vents (and your picture) imply that you have a "one pipe" steam system, where the pipes are sloped to allow condensed water to flow back to the boiler while steam flows to the radiators above that. The air vent allows air out of the system and then closes when it heats up as steam gets to the radiator.

A search on Hoffman Adustable Valve comes up with

Adjustable port for true proportional venting v 6 port settings from slow (1) to fast (6)

Which appears to be "1 is less and 6 is more"

The supply valves (as you suspect) should be fully open (unless someplace is so overheated you don't want that radiator to heat at all.) Do check that the upstairs control valves (on the steam pipes) are fully open.

It is possible that (some of) your air valves may not be operating as they should, and need to be replaced with ones that do. You could certainly try moving some of the "too warm" rooms from 2 or 3 to 1 or 2. It might be worth trying turning the upstairs air valves down to 1 and then back up to 6 - but they might need to be replaced. You should hear air coming out of the vents when the boiler starts up.


Steam systems work on a fairly simple principal. Boil water into steam, it expands into the piping then to the radiators. The steam pushes out the air and heats the radiator, then cools back into water and flows back to the boiler via gravity to be reheated. There are several conditions that can cause your issues. The radiators closest to the boiler will heat the fastest. If your thermostat happens to be in that room the boiler will shut down before the rest of the radiators have steam. The steam vents can become clogged with minerals in areas with hard water. If the air can't get out, the steam can't get in. You are correct in using the vent to slow down the heating of some radiators to allow the others to heat. This is how the system is balanced. If the pipes in the basement aren't well insulated the steam will condense back to water and not heat the radiators. The horizontal pipes must have a slight upward pitch toward the radiators. This allows the steam to rise and the condensate to return. The steams flows away from the boiler on the top part of the pipe. The condensate returns to the boiler on the bottom part of the same pipe. The radiator should have a slight pitch, with the vent being on the higher side and opposite of the inlet valve. To trouble shoot the system, turn the heat up to a higher than normal temp. Check each radiator vent to see if there is air escaping. Feel each shutoff valve to see if the pipe is hot before and after the valve. The difficult part is if you have an issue other than a clogged vent it is difficult for a home owner to do a repair. Replacing a broken shut off valve usually requires smashing the valve as 100 year old cast pipes don't easily disassemble. I would recommend having your heating contractor do an inspection and get their input.


I assume you've made sure all the radiator steam valves are open, it's possible with empty nesters they may have turned off some of the radiators.

If not I would try is cleaning the upstairs steam vents, that silver thing on the right side in your picture. With the system cold and the heat turned off, you can simply unscrew that (very carefully*), open it all the way to 6, blow it out, soak it in vinegar or CLR cleaner, rinse thoroughly, wrap the threads with teflon tape, and reinstall it.

If you can't get them clean, you might have to replace them.

I say "very carefully" just because you don't want to turn a small problem into a large problem, especially not with an old heating system in January. If these are rusted in place things quickly become more complicated.


Start by bleeding them. You may need a radiator key. You can get it at the hardware store.

  1. Go to your boiler and make sure you have pressure 15-19psig
  2. Start at the highest elevation, slowly crack it open until only water is coming out
  3. Work your way down the lower elevations.
  4. Do this yearly. More if you have a slow leak.

Then you can adjust as necessary. Be careful, if you have an excessive amount of resistance or none at all in the valve. you may want to leave the valve alone. You can get them replaced with quarter turn ball valves, but do it in warmer weather, as you need to drain the system.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.