5 Steps to Healthy Steam Radiators

A simple checklist for solving five common problems with your steam radiator

* This is from an article written in 2012 (an old print issue of our newsletter. Click here to view it!)

      Every winter, especially when it begins, we receive many calls about the steam radiators acting up.  Residents hear loud clanging, banging, knocking, hissing or other strange noises from their heating pipes, feel too much heat or even no heat at all. Sometimes, residents alert us of leaking water or escaping steam from the radiator, leaving the apartment walls or floors wet or feeling damp.

       Someone is always inconvenienced when things go wrong with a radiator, whether it's the resident who needs the radiator repair or her downstairs neighbor, who's become the unwilling recipient of water that has found its way from the radiator into his apartment. 

      The good news is, such problems are often avoidable and sometimes, surprisingly easy to solve. With some vigilance and by abiding some rules-of-thumb, we can usually prevent these issues from happening or at least catch them before they cause unnecessary aggravation or serious damage.

     Let's begin by looking at how a one-pipe steam radiator works.*

How a Steam Radiator Works

As shown above, the main parts of a steam radiator consist of two valves, the supply (or "radiator") valve and air (or "vent") valve, and the cast-iron radiator body. 

      When the boiler is triggered and steam is generated, it flows from the boiler by a series of pipes and enters the radiator body through the supply valve. In the above animation, the green arrows represent steam. 

      As the steam fills the radiator body, it pushes out the cool air (blue arrow), which escapes through the air valve. When the air has left and the steam fills the radiator body to capacity, the air valve senses the steam and automatically closes to trap the steam inside. 

      The steam then heats the metal fins on the radiator, which warms the room. 

      Finally, the steam cools down and reverts to water, called condensate (red arrow), and then flows out of the radiator through the supply valve back to the boiler. 

      So, now that you know how a steam radiator works, what does this tell you about problems below?  Let's look at these common issues more carefully.

Which problem do you have?

      But, before we move forward, let's learn how to use your radiator's supply valve.  This is important because most of these issues below and the immediate action you'll most likely need to make in case of an emergency is to cut off the steam to your radiator.  This is done by turning the handle on the supply valve.

How to turn off your steam radiator:

      The supply valve should be located towards the floor close to or right beside the radiator body. It's metal and should have a round handle on top.   It normally looks like this:

      To turn off the steam to the radiator, turn the handle all the way to the right (clockwise). The radiator should cool down as the steam cools to condensate and air fills up the space inside the radiator. 

      As a warning, remember to keep the supply valve either all the way on (to the left) or all the way off (to the right).  Do not keep the valve turned halfway or somewhere in between.  The supply valve does not regulate the temperature and should only be used to permit or stop the steam from entering the radiator.  

      Read the book by its cover.  If the supply valve is rusted, has a broken handle, or just looks like it has seen better days, look to replace it as soon as possible. 

Problem #1: Too Little or No Heat

      If you're feeling little or no heat, the possible reasons are that the supply valve is closed and / or the air valve is not working properly.  Let's look at these possible issues one at a time:

Reason #1: Closed supply valve

      The supply valve controls the steam coming into the radiator.  If it's closed, then the steam can't enter your radiator and metal fins will be cold.

      Contrastingly, is the supply valve warm to the touch?  That means the steam has reached the radiator but stopped short at the supply valve.  

     Try turning the knob slightly counter-clockwise to open the valve.  If the supply valve seems to already be open, or doesn't budge at all, then move on to the next step.

Solution:

      If your supply valve is stuck, you can try to loosen it with hand pressure.  Do not use tools to apply force.  Excess force could break the supply valve and remove the last line of defense against a full blown steam surging into your apartment.  Call in a repair pro or your building super if pressure by hand doesn't work.  As a last resort, replace the supply valve.  

Reason #2: Air valve stuck closed  

        A failing air valve can prevent the radiator from getting hot.  In order for steam to enter the radiator, the cold air needs to escape from it through a tiny hole in the air valve. If this air valve is clogged or stuck, the cold air will be trapped inside the radiator refusing to let the hot steam enter and do its work. 

Solution:  

      When your radiator body is cool to the touch (or even partly cold) and all else is checked to ensure that there's steam in the pipes, you simply may have to replace your air valve.  

      You can most likely find the correct replacement air valve at the local hardware store.  When you have the right air valve and prepared the work area, you need to shut the supply valve to close the steam to your radiator (But before you do it yourself, read this first!).

Problem #2: Hammering, Clanging, Banging or Knocking

      Basically, the occurrences of banging, knocking or other similarly jarring noises happen when the cooler condensate returning to the boiler encounters the hot steam and then a violent expansion and contraction takes place.

      These sounds can emanate from anywhere in the building's heat pipes where the condensate has backed up and its encounter with pressurized steam is unavoidable.

      But, when these sounds seem close by, your own radiator may be the culprit.  Condensate can become trapped at the bottom of your radiator and create a "water dam" that is ripe for an epic showdown with the steam flowing in.

      So, why does this steam condensate pool at the bottom of the radiator and what can you do about it?  

Reason #1: Supply valve turned halfway:

      A common mistake many people make is leaving the supply valve on their radiator partially open or closed on the assumption that the rotating handle can dial the heat up or down incrementally.  The fact is that the supply valve does not control the temperature and, rather, the only two states to set the valve is either fully open or fully closed.  There is no middle ground. 

      When the supply valve is left open in a halfway position, it physically blocks the condensate from flowing out of the radiator while the steam tries to surge in. This violent interaction between the two warring states of H2O takes place and the dread noises are created.

Solution:

      To solve this problem, first, open your supply valve all the way to let the water drain out.  

      If water remains inside, you'll need to disconnect the radiator body from the pipes and drain the water out.  Water remaining inside the radiator can cause serious problems down the road, so you'll want to address this as soon as possible.  

      As the radiator body is often very heavy and since disconnecting it involves special tools and experience, this should be done by a professional or the Building Super. 

      If you've found an issue described above, or need any help in doing so, give us a call and we'll be happy to give you a hand. 

      Steam radiators must be pitched slightly towards the supply valve so that the condensate can easily drain out from the radiator (in other words, the air valve side of the radiator must be elevated slightly higher than the other side that is connected to the supply valve).

      If the pitch is not enough to drain the condensate out of the radiator, it will pool at the bottom of the radiator body and block the entry of steam, causing the banging, clanging and other unpleasant noises.

Solution:

      If you cannot tell by simply looking at it, you can check the pitch by placing a bubble level on top of the radiator. It should be pitched towards the supply valve.  

       If it isn't, carefully lift the end of the radiator that seats the air valve and try to elevate it by wedging a firm, flat piece of wood beneath the feet just enough to raise it slightly over the other end (with the supply valve).  

     There's other ways that a radiator can be pitched the wrong way to cause problems, but this is the most common problem.

     This is a repair that should be performed by someone with experience, like your building super, so read this first. 

Important

      Condensate can be very corrosive to metal and eat away rubber gasket, washer and seal inside the valves. So, if you hear hammering, banging and other loud noises, and find that the pitch of your radiator is off or your supply valve is only partially turned, address this right away. The longer that condensate sits idle inside your radiator, the more damage it can cause to its cast-iron body and valves, leading to unforeseeable water leaks and related expenses.

Problem #3: Hissing, spluttering or other strange noises

      A normal radiator should not emit any noises.  Any hissing, spluttering, spitting, gurgling, whistling or other strange noises should flag that something is wrong and needs to be looked at.

Reason #1: Air Valve stuck open:

      Air valves are meant to release air, but never any steam. Moreover, when air is released through air valve, it should exit quietly. If the air valve releases steam or makes strange noises like excessive hissing or whistling, it should signal that something is wrong with the air valve and that perhaps it is ready for replacement.

      Ignoring these noises can be costly down the road.  

• Energy (which equals money from someone's wallet) is wasted through the escaping steam
• Escaping steam eventually reverts to water outside the radiator, leaving destruction on the walls, ceilings and floors around the radiator or even inside the apartment downstairs

Solution:

      If the air valve is stuck open, you can clean it with vinegar and see if this works to remove any possible blockage.  However, you may want to just replace it, especially since air valves are relatively inexpensive these days and easy to find a local hardware store.

Reason #2:  Air valve wrong size, type, pitch, etc.

      Gurgling or other spitting sounds may indicate that water is getting trapped inside the air valve.  Air valves should not leak or trap any water.  If it does, it may be that the air valve is installed or positioned wrong, or is the wrong type for your radiator.  

      The air valve should be connected to the radiator by screwing into the radiator body to create a snug, air tight seal.  Condensate may leak when the metal threads inside the radiator body are ruined and not holding tight, or if there's a mismatch with the threads on the air valve, leaving it wiggling loosely.

      Also, you will need to look at the orientation of your air valve. It must be positioned right-side up so that the air hole is pointing straight up, or on some valve types, turned to sit at the highest part of the body.  An air valve shouldn't be leaning over or pointing sideways.

       Using the wrong air valve type can lead to similar issues.  

      There's different valves, for instance, with different shapes depending on where or how it screws into on the radiator. 

      There's also different-sized air holes, depending on how far your radiator is from the boiler.  

      So, if you're on the highest floor (furthest from the boiler), the bigger the hole should be.  Conversely, the closer your radiator is to the boiler, such as an apartment on the first floor, the smaller the air hole should be.  The principle behind this setup is that every radiator in the system warms up at the same time and no apartment is overheated before another one starts to warm up.

Problem #4: Water leaking from the radiator

      By far, the most common type of emergency call during the heating season is a water leak from a steam radiator.  The lucky calls are from those who catch the leak quickly from their own radiator.  But, more often are the calls from a distressed neighbor who lives below the leaking radiator and is finding the condensate winding its way - surprise! - down into her apartment. 

      Damages to property and a neighbor's frustration may be reason enough for you to head out looking for possible leaks around your radiator, but the possibility that it can foster mold and mildew inside your apartment or within the cavity of the walls may seal the deal for you to proactively tackle this problem before it becomes progressively worse. 

      Take a look around your radiator.  Are there any traces of water or moisture?  The water may not be visible but if there is a leak, you're bound to see its damaging effects on the surrounding wall or on the floor beneath.  It can look similar to the one in this photo, right at the supply valve shutoff: 

      In this photo below, the source of the leak is apparent - no mystery involved.  Wall damage has appeared where the air valve and its vapor-spewing hole are positioned, a dead giveaway. The damp discoloration at the radiator's foot is also strong indication that the air valve is leaking and should be replaced.    

      However, it's not always easy to spot where the leak is coming from. That's because the radiator is a piping hot vessel where the two H₂O states of pressurized steam and water co-exist side-by-side, and can escape to the surrounding areas through openings the size of pinholes. 

Water Leak #1: From the Air Valve 

Coming soon!       

Problem #5: Too much heat 

      A radiator pumping out too much heat can be just as unsafe, frustrating and indicative of problems as one that is frigid and seeming not to work. When it comes to overheating, however, only few issues can be fixed from the point of the radiator; most issues are caused by things that are likely beyond your immediate control, such as the boiler control settings or imbalances in the heating system caused by other apartments.

      Even so, the good news is that you still have some options.

Overheating Solution #1: Close the supply valve 

      The supply valve on the radiator controls the entry of steam into the radiator body.  Closing this valve prevents the steam from entering, thereby keeping it from getting hot.  This was covered above here. 

Overheating Solution #2: Cover the radiator 

      Covering the radiator with an enclosure can help to reduce the heat. Popular options are custom-fitted covers made of wood with perforated metal sheet on its face to allow in some heat, as shown below.

      One urgent reminder: whichever material or style you use for your radiator cover, make sure that it can be removed quickly and its valves can be reached easily in case of an emergency.  Your building super will be thankful if s/he doesn't have to dismantle anything as he rushes to turn off the steam to the radiator. 

Overheating Solution #3: Paint the radiator

Overheating Solution #4: Install a Thermostatic Radiator Valve

      Installing a thermostatic valve can actually help to regulate the heat (in ways that many mistakenly try with the supply valve). 

      Basically, this device consists of two parts: a thermostatic head, which senses the room temperature around it and expands or contracts, and an actuator valve, which closes the flow of air when the temperature reaches a set point.   

      Set the dial on the thermostatic head to your desired temperature, and watch your radiator work like your own personal boiler.

Overheating Solution #5:  Remove the air valve

      Another way to stop the steam from entering your radiator is by removing the air valve permanently, then closing the hole with a metal plug.  Doing this prevents the cooler air from exiting the radiator, thus, creating a barrier for the steam to enter. 

      The plug is threaded so it will screw right into the hole where the air valve once was installed.

      Remember to turn off the supply valve before attempting this, or during the warmer seasons while the boiler is turned off.

      A warning shared by professionals is not to do this, since doing so creates imbalances in the system.  Ask your building super before you attempt this. 

      Oh, yes, one more thing. It's not in the illustration below, but remember to use teflon tape to create an airtight seal between the plug and the radiator hole.  

      So, we've covered the five most common problems with a steam radiator and the ways to solve them. 

      Discovering them during the winter season and trying to fix them while the heat is on full blast can be aggravating and even dangerous. Is there a way to address to these before the heating season is underway?

      You betcha. 

      The good news is that most of these problems are preventative and can be part of your annual checklist.  if you've read this article, you're already miles ahead in knowing what to look out for.

       To make it easier, I've compiled a checklist below.       

for your Steam Radiator

1. Test your supply valve.  Does it turn smoothly in either direction?  Note the condition.  Is it rusty or in good condition? Turn the supply valve all the way off or on. Never in between. 
2. Visually inspect the air valve:  Is it positioned right-side up?  Are there visible water marks?  If there is evidence of water leaking, replace the air valve.  Remember to use teflon tape, which creates a water-tight seal on the threads. 
3. Check the pitch: Make sure the radiator is pitched so the condensate is able to flow towards the supply valve.
4. Check for water damage around the radiator: If it looks like there's been past damage, check it right away. Don't put it off until the damages get worse, or it even travels to other apartments.  
5. If your radiator seems like its seen better days, think about giving it a fresh coat of paint with a rust proof high heat paint.