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Radiator valve inspection & troubleshooting:
Here we explain the use, adjustment, diagnosis & repair of hot water or steam heating radiator valves & steam vents to control heat output from individual radiators. What to do about hot water or steam radiator valves or vents that are stuck open or closed.
Which way to turn the radiator valve to open or close it. How to replace a leaky or stuck heating radiator valve. Install a thermostatically operated radiator valve.
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Guide to Using, Adjusting, Diagnosing & Fixing or Replacing Hot Water or Steam Radiator Control Valves & Vents
Traditional "Manual" Radiator Valves
Radiator valves are opened to allow hot water or steam to enter and heat a radiator, or closed to turn off or reduce heat output from the radiator. By "manual" radiator valve we mean that you have to turn the valve open or shut yourself. We discuss automatic (thermostatically controlled radiator valves and other radiator controls below.
At above left is a top-fed two pipe steam radiator at Google Headquarters in New York City.
If your heating system radiators won't get hot, for hot water radiators or convector heat,
see COLD STEAM HEAT RADIATORS for help in diagnosing the problem.
If your heat is provided by baseboards there will not normally be individual shutoff valves at those devices, but if your system uses one circulator and provides multiple heating zones (and thermostats) there will be zone control valves (usually near the boiler) that are opened or closed by the room thermostat(s). Cold heating baseboards are discussed
Which Way to Turn the Radiator Valve
If your heat is provided by individual hot water radiators or convector units, usually there is a control valve at each radiator or convector. Make sure that the control valve at the heating radiator is "open" or "on". Usually turning a radiator valve "clockwise" or "down" closes the valve (turns the heat
At COLD HOT WATER BASEBOARD / RADIATOR we include links to additional detailed articles that will help you correct a problem with heating baseboards or radiators that are not working:
Check the radiator control valve: If a radiator is not getting hot: (steam or hot water) first see if the valve that controls it has been turned off. Try turning the valve counter-clockwise to see if it will open.
In our photo (left), the heating convector control valve was found at floor-level under the heating convector. The "open" and "close" directions for this "radiator valve" were nicely marked by the manufacturer (click to enlarge the photo).
If the radiator valve does not turn in that direction, try turning it in the other direction (clockwise or "closed") to see if the radiator valve is stuck. You may also find the same control valve at heating convectors (but not usually at heating baseboards).
While people sometimes turn off radiators in an un-used portion of a building we usually find that most radiator valves have been left in the "on" position - in fact turning off a hot radiator in some building areas could lead to its freezing and cracking.
Steam radiators, on the other hand, can usually be turned-off with impunity since steam radiators do not normally contain water in its liquid form. [That's true at least so long as condensate has not become trapped inside of the steam radiator.]
Watch out: don't use excessive force to try to turn a "stuck" radiator valve. First, you may be trying to open a valve that is already in its fully-open position. Second, the valve may actually be jammed. Excessive force can break the valve or even cause a leak. If the valve won't turn at all counter-clockwise towards "open", try turning it the other way - clockwise, towards "closed". If the valve now turns you'll know it was already in its open position.
Watch out: even if the radiator valve appears to be "open" - that is, turned fully counter-clockwise, if the radiator valve stem is broken internally you may be just turning the knob but the valve may be staying closed inside.
If your radiator valve turns too easily or if it does not appear to raise (opening) or lower (closing) when turning, and especially if turning the valve makes no difference in the behavior of the radiator, the valve stem may be broken. (First check for air bound radiators or if your heating system uses steam, check for a steam vent that is not opening.)
Usually while turning a radiator valve to from "closed" to "open" position, if you look closely at the valve stem - the metal rod or shaft extending below the knob you are holding, and extending into the body of the valve itself - you'll see that as you "open" the valve the stem gets "longer" and often a less-oxidized, shiner part of the valve will become exposed as it moves upwards from having been inside the valve body.
That's a great way to convince yourself that yes, the valve is probably opening internally too, you're not just turning the knob. If the valve body has broken loose from the valve stem, that's an internal problem you can't see, but turning the radiator valve knob, even if it rotates, will not open a broken, stuck, frozen valve.
If only some of your hot water radiators, hot water heating convector units, or hot water baseboard heating sections are not getting hot and the radiator valve is open,
See RADIATOR STEAM VENTS and
also STEAM HEATING SYSTEMS for details.
Hot Water Heat Radiator Valves
In our photo at left you can see not only the radiator control valve, but lots more information:
This radiator is being fed from the top. We know that this must be either a hot water radiator or a two pipe steam heat radiator.
Now look closely at that air bleeder connector on the side of the radiator valve.
From this detail we can conclude that this is a hot water heating system, not a steam heat system
Hot water can enter a hot water (hydronic) heating radiator at the radiator top or bottom. Hot water radiators may have an air bleeder valve but never a steam vent valve.
Steam can enter a steam heating radiator at the radiator top too (most but possibly not all two pipe steam heat systems) or also at the radiator bottom (one pipe steam heat systems).
Steam Radiator Control Valves
If your heating system uses steam radiators or steam convectors see
First check the radiator valve. It's standard to ask first "is the radiator valve turned on or "open" (fully counter-clockwise)?
But other problems can cause a steam heat radiator to stay cold when you want heat.
If a steam radiator valve is open but the radiator is still cold, the steam vent may not be working.
Our photo (above right) shows a typical steam radiator vent.
See STEAM RADIATOR PIPING CONNECTIONS for an explanation of different types of steam piping and steam-radiator piping connections.
Also see STEAM VENTS and
Reader Question: where do steam pipes enter steam radiators: top, bottom, or both?
I’m looking at the sub-section “Types of Radiator Valves: Hot Water vs. Steam” ...
Photo at left: two pipe steam radiator fed from top right end. [Click to enlarge any image]
I was trying to make sense of what was written - it must be hard to describe these hot water and steam heating systems. In some cases it seems that in fact steam DOES often enter a radiator at the top.
At this point I am just lost. We don’t have many residential systems with radiator systems (steam or hot water) so I am trying to educate myself but don’t have anything in front of me to compare what I think I understand.
Kind Regards, -Doug
Reply: Up-feed - Down-feed, One-pipe - Two-Pipe Steam Piping & Radiators - What's the Difference?
Doug, the other page (not at InspectApedia) that you gave provides information from Dan Holihan - probably the most-expert fellow alive when it comes to steam heating systems. Dan's text includes these two statements:
Dan is right again. Most two-pipe steam heat systems will show up with the steam entering the radiator at one end at the radiator top (below left), and the condensate return will exit at the bottom of the radiator at its opposite end. 
All one pipe steam radiators are fed with a pipe connection to the bottom of the radiator.
In response to your question we have added an article to help clarify the different types of steam heat piping - to - radiator connections and where valves will occur. Please
On a heating convector unit there is usually an individual valve that lets the unit be turned down or off - but as our photo (left) shows, the valve can be a little harder to spot.
This valve, if it's not jammed by corrosion, is operated by a screw driver; it may be possible to get this valve working by gently loosening the lock-nut and then turning the control screw with a flat-bladed screwdriver.
Do not take apart this valve while the heating system is on and hot - you risk getting sprayed with hot water or you may start a leak that's hard to stop without making a mess and having to shut down the whole heating system.
Manually Setting the Radiator Valve
On hot water heating systems and two-pipe steam radiator heating systems you can adjust the radiator valve to:
If your hot water radiator is too hot or the room is too hot, you can partially-close the radiator valve.
If your hot water radiator is too cold, be sure that the valve is open and that the radiator is not air bound. Details are
If your steam radiator is too cold be sure that its supply valve is open. If it's a one pipe steam heat system (only one pipe comes to each radiator), be sure that the steam vent is working (you should hear it hissing when steam is rising in the system). Details are
If you steam radiator is too hot in a two-pipe steam system, according to the U.S. DOE,
If your steam heating system pipes are noisy
There are additional methods for automatically controlling the heat output from individual heating radiators, for both steam and hot water heat: thermostatically controlled radiator valves and adjustable or thermostatically controlled steam vents. We discuss these controls beginning
The radiator control valve opens or shuts to allow hot water or steam to enter and heat the radiator. An automatic or thermostatically controlled radiator valve allows you to set the desired room temperature.
The automatic hot water or steam radiator valve, thermostatically controlled, will automagically open or close to attempt to control room temperature to the desired level. Keep in mind that with any heat control installed right at the radiator, the control will be sensing temperature in that location, not across the room, so some experimenting to find the best setting will be needed.
Armstrong Corp. provides the RV-4 One-Pipe Steam Radiator Valve that operates as a room thermostat suitable for residential low-pressure steam heating systems. By installing a thermostatically controlled steam vent at each radiator, every radiator can be controlled or set to the desired temperature.
There is a central advantage of thermostatically operated steam vents over swapping out the actual radiator control valve for a thermostatically controlled radiator valve, that is, they are easier and less disruptive to control. The original steam vent is simply unscrewed and the new thermostatically controllable steam vent is screwed in at the same location.
Watch out: it's safer to install or change steam heating system parts when the system is not calling for heat and when the steam boiler and radiators are cold. Don't be fooled. If your heating system is on and the steam boiler is hot, unscrewing the steam vent on a "cold" steam radiator will allow steam to rise into the radiator (forcing air out of the steam vent opening) and you could be seriously burned by rising steam.
Replacing Manual Radiator Valves with Thermostatically Controlled Radiator Valves
If you have to replace the control valve on a hot water or steam radiator or convector unit, consider installing a new valve that incorporates a thermostat as well.
Several companies provide thermostatically-controlled radiator valves including Armstrong, Danfoss, Hoffman Specialty, Jacobus (Maid'O'Mist) and others. The automatic radiator valve shown at left was observed on a typical modern European installation in Molde, Norway.
This (more expensive) radiator control valve lets you treat each individual radiator as a "heating zone".
As long as the room thermostat is calling for heat, each radiator can be regulated automatically when a thermostatic radiator valve (TRV) is installed..
This topic has been moved and consolidated at STEAM VENTS - home, where we discuss other steam vent problems such as spitting water, clogging, steam valves that do not open or close when they should, etc.
At STEAM VENT TYPES, SELECTION we identify the different types of steam vents use on 1 pipe and 2 pipe steam systems.
This text has moved
Watch out: If the radiator continually makes noises (whistling or wheezing) at the steam vent, there is a problem that needs to be fixed: a bad steam vent, steam piping problem, steam pressure set too high, or boiler oversized for the heating distribution system.
Watch out: to be sure your steam heating system and its controls are properly adjusted excessive steam pressure can be dangerous.
Continue reading at STEAM RADIATOR PIPING CONNECTIONS or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs)
(Nov 7, 2012) Anonymous said:
Great articles here. Very informative.
Question: steam vent won't close
(Oct 24, 2011) Lisa said:
Trying to figure out vent problem without calling plumber before heating season. Last season one room was totally ruined by steam and dining room seemed to have too much steam. New vents installed on radiators when new gas steam unit installed 6 years ago. Vents have #s on them. Should I put it on lower #?
Lisa i would need to see a photo of your steam vent or know the brand and model number to be specific. But if you have steam vents that never shut off when the radiator is hot, and if adjusting the vent doesn't solve the problem it sounds as if the vent needs to be replaced. . A properly operating steam vent will stop venting air (and a little steam) when it gets hot.
See STEAM VENTS - home
Question: can't get air vent valve out of the old radiator
(Sept 20, 2012) donna said:
We just bought an old home and the one rooms radiator air value must be broken so I can't put another in how
The options are to try a bolt extractor to remove the broken part or to drill out the broken part and tap new threads in the drilled hole. Then to reduce the enlarged threaded opening to a standard air bleed valve NPT size you may find a helix insert at an auto or plumbing supplier.
Question: removed two pipe steam radiators - want to turn on heat
(Oct 10, 2012) Mike said:
I am currently renovating a room in my house and I removed two two-pipe system radiators. I am not ready to re-install them yet but I would like to turn the heat on. Will shutting off the valves be enough or will I need to cap off the traps as well?
Heat will work in the other radiators provided they are not fed by the pipes you close off and that their return condensate lines are similarly not interrupted. You'll need to follow the steam piping to make a sketch for yourself to see that this is the case.
Question: wants to buy adjustable thermostatically operated steam vents
(Oct 11, 2012) Anonymous said:
Can you please tell me where I can buy the Adjustable Thermostatically-operated steam vents?
Sure. Several companies provide thermostatically-controlled radiator valves including Armstrong, Danfoss, Hoffman Specialty, Jacobus (Maid'O'Mist) and others. The automatic radiator valve shown at left was observed on a typical modern European installation in Molde, Norway.
Question: convector radiator valve leaks at screwdriver adjustment point
(Nov 20, 2012) Brent Hoffman said:
On my hidden manual convector control valve, how or can i clean and repair it so i can adjust flow with out it leaking at the screwdriver adjustment point. The last time I tried to increase the flow by turning the adjustment screw, I almost didn't get it to stop leaking. Is it like a faucet that I can open and get replacment parts to repair and rebuild?
If so, if I lower the expansion tank preasure noting the current preassure first, will that allow me to repair the valve with out loosing water? If i loose water in my convector boiler system, how do I refill and know when it is full. Each one of my convectors feed from a 1/2 service line with a 3/8 feed line to the convector and return through a 3/8 to a 1/2 return line, i do not have a series system loop.
Brent, it is sometimes possible to disassemble and clean up the small screwdriver-operated valve you describe but I've not had much luck with that approach. With heat off and pressure off of your system, remove the old valve, take it to your heating supplier and buy a replacement - they're not expensive and you'll actually save time and trouble as well as money.
Question: heat won't turn off
(Nov 28, 2012) Aimee said:
Hi there, i really need some help . My radiator is really hot even though i already turn off the switch. Are there anything wrong ? If some thign wrong , please let me know ? thank you so much .
Aimee a hot water or steam radiator will continue to radiate heat for a time even after the thermostat stops callling for heat. That's normal. If the radiator never turns off then the call for heat is not turning off. In that case
Question: strange boiler noise and no heat
(Nov 29, 2012) Sof said:
Hi,I had some painters over to decorate and they turned off the radiators so the wallpaper wouldn't shrink whilst drying. Normally, to turn the heating on I just push the 'On' switch on my boiler.
Now though, by doing so the boiler makes a bit of a strange noise. The water stays freezing cold and the radiators wont heat up even though I've pushed the 'On' button. This means that the builders turned the heating OFF elsewhere to ensure I don't turn it on. Now my house is freezing and the water's too cold to was up or have a shower. What could I do?
Sof there is a more basic problem than at the radiators - see NO HEAT - BOILER for a sequence of things to check.
Question: steam enters at top of some steam radiators
(Jan 5, 2013) Caroline said:
Hello, I just wanted to inform you that you need to correct the information on your site. This section: Types of Radiator Valves: Hot Water vs Steam and the the statement "because first, the valve is mounted at the top of the radiator (water, not steam - steam enters at a radiator bottom but sometimes so does not water; the reverse is never true" is not correct. We have a two pipe steam radiator system and the valve is mounted just as shown in this picture - so our steam does enter from the top of the radiator.
Thank you Caroline, we've reviewed and clarified the text on this point.
Question: radiators don't get hot unless I remove the steam vent
(Jan 7, 2013) Cesar said:
We have two radiators that don't heat up unless I remove the steam valve. When I unscrew it a blast of air comes out and it starts to heat up. We figured the valves were clogged but they're not because when we screw them back on we can hear steam hissing out. My question is this: why doesn't it release the steam all on its own? why do I have to remove the steam release valve in order to get it going?
The steam vents on those two cold radiators are not working as they should. Take them to your heating supplier and buy new equivalent replacement units and your radiators should work perfectly again.
Question: different steam vent locations on one pipe versus two pipe steam systems
(July 12, 2014) Jerry said:
I have a few questions on one and two pipe steam systems. On one pipe systems, why is the steam vent located down low on the radiator and not high up like on hot water radiator systems. What would happen if it was located high. My question on two pipe steam systems is why no vent is needed on radiator? What would be the result if one was installed?
In a hot water radiator the air will be just at the top of the rad so we put the air bleeder there.
In a steam system the whole rad is filled with air when cool and is vented automatically by a steam vent placed to vent rapidly and to close at an appropriate time as steam enters and the radiator becomes hot. Placing the steam vent at rad top may lead to overheating.
If you see a working 2 pipe steam system without a steam vent the air along with condensate must be vented via the return line.i do not agree that vents are unnecessary on either system type.
Questions & answers or comments about using, adjusting, & repairing radiator control valves and vents for both hot water and steam heat systems
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