Questions & answers on how to diagnose & fix a too-cold steam radiator.

These frequently-asked questions about steam radiators that are not working, cold radiators or sometimes radiators that are too hot, will help you diagnose and fix the problem.

This article series describes the diagnosis & repair of cold steam heating convectors or steam radiators. We list less common causes of cold steam radiators in buildings and we describe how to fix these conditions.

Our page top heating system illustration was provided compliments of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

Cold Steam Radiator Diagnosis & Repair FAQs

Steps to fix a single cold radiator

One of my radiators is cold The valve is new - (Feb 11, 2016) Anonymous

We have a steam heat system where all of the radiators are warm except one. We followed the pipe back from the radiator to the floor below. In the room below, the pipe is hot near the floor but have way up the way it goes cold.

There is not connection point or valve in the pipe that could explain it. Is it possible that something is clogged in the pipe half way up the wall. If that is possible, how do we clear the clog? - (Nov 20, 2016) Karl

Reply:

Anon: Check that the valve is open and that the steam vent is working. As it's just one radiator we know the problem is local to that heating device.

Karl: sure, if the radiator's steam vent is not working or its valve is stuck shut that could explain the situation you describe.

Start by close examination of the steam valve at the radiator to be sure it's open. Beware that a broken valve stem can turn without lifting the gate inside the valve: fooling you.

Next, replace the steam vent with a new one of the same model or capacity.

Last, check the steam trap at the radiator for clogging.

Watch out: Do steam radiator work with the heat off and the radiator cold. Otherwise rising live steam can cause big trouble when you've got the piping or radiator open.

 

Why can't I get heat to the large steam radiator on the first floor?

I have steam heat on two floors. The 2nd floor gets too hot and has 6 one pipe radiators with angled steam valves attached.

The first floor has 3 radiators. They are all two pipe radiators and they all have angled steam valves like the ones on the second floor.

The smallest radiator on the first floor gets hot and so does the farthest large radiator. The radiator closest to the boiler on the first floor, which is large, does not get heat. Up to its supply valve i get close to 100 degrees while the rest of the radiator is cold.

Upstairs the one pipe radiators are all too hot and avery about 150 degrees at the same time. In the basement not far from the boiler the main return has a Gorton main steam valve.

Why can't I get heat to the large radiator on the first floor? Can i use TRVs to regulate the heat on the second floor? On 2022-12-27 by Z11542

Reply by InspectApedia Publisher -

@Z11542,

When some steam radiators on a piping loop get hot and others don't, I suspect a closed or jammed radiator valve, a clogged or defective steam vent, or on occasion a problem with blocked condensate return.

The fact that one of your rads gets hot on one end suggests that it's having trouble returning condensate. An experienced plumber or heating service tech may be able to dis-assemble and clean the rad bottom or pipe connections, but that's a bit inconvenient in the middle of cold weather.

And yes, for more-careful control of individual radiator heat output you can certainly install thermostatic radiator valves (TRVs) on any of your radiators.

Again, not so convenient to do during the heating season, but if you've got enough work to make the job interesting to a heating service company they might be willing to send enough experienced technicians to first survey for what's needed, then return to do the job quickly enough that you don't freeze.

Details of heating radiator troubleshooting and repair are given starting at

RADIATORS for ROOM HEAT - home

and be sure to see (among the plethora of radiator repair articles there)

STEAM HEAT RADIATOR REPAIR - diagnose & repair

and

AUTOMATIC RADIATOR VALVES - Automatic or Thermostatically Controlled Radiator Valves

 

One of two radiators won't get hot

Hi I Have a Question about my Radiator. I HAVE Two Radiators One one each corner of the house one gets Hot one is cold .

On the Radiators do thE Shut off VALVES Hot and cold need to be open at the same Time Hot water does run down the pipe to Radiator.

DOES not run into Radiator. Thank you - On 2020-11-24 by Peter Gruber -

Reply by (mod) - be sure the valves are open at both radiators

Peter

Each radiator has its own control valve; both need to be open if you want both to produce heat.

I would not expect both "hot" and "cold" valves to be present at a heating radiator, just a single control valve at each radiator.

If you've got something different, perhaps you can use the "add image" button to post a photo.

 

I think my steam boiler pressure is too low to get heat upstairs

The psi for water pressure does not increase when furnace is running so no heat second floor - On 2020-11-15 by Bob -

Reply by (mod) - check the actual pressure and don't trust the gauge

Bob:

You are commenting on a steam heating page so I'll assume your boiler is a steam heating system.

Residential steam heating boilers operate at a very low pressure typically under one psi. So looking at the pressure gauge on your boiler is not going to be a complete diagnostic and in fact if the gate shows no change at all with the boiler heat up I suspect that the gauge itself is debris clogged and might want to be replaced.

So if you have no heat on an upper floor in your home and it's steam heat the most likely the radiator steam vent or vents are not working on the radiator valves are closed.

 

Some steam radiators are not getting any steam at all

I have an apt block floors 2,3,4 no problems 1floor 2 front apts and 1 back apt no heat to steam radiatos all line vrnt and radiator vents replaced i took out the line vent in basement no steam comming out boilet was running for 45 min plugged main sumwhere? - On 2018-01-06 by Anonymous -

Reply by (mod) -

Anon if burner is operating but the boiler is not producing steam TURN IT OFF and call for service - the system may be unsafe, out of water, and risking boiler damage too.

Start by looking at the water level in the boiler.

 

Our steam radiator doesn't have a vent and does not get hot

We moved a steam radiator in a bathroom second floor. The radiator builds pressure the system has no vents at the sources of heat.

We tried replacing the steam trap thinking it was our problem.

Feed pipe coming out of the wall is pretty hot but pretty much stops at the 90 coming out of the wall. - On 2017-12-14 by Anonymous -

Reply by (mod) - no vents found on two pipe steam heat radiators; here's what to check

Anon,

For a typical residential one-pipe steam heat system,

your steam radiator won't heat if it cannot vent air in the the radiator from its cold state. Each steam radiator normally requires its own steam vent.

If your steam heat is a two-pipe steam heating system

the radiators often don't include a steam vent. On a two pipe steam heat system, as steam heat rises, the air in the system is vented or released through vents on the steam main line.

So first let's identify the type of steam heat that you have: one pipe into each radiator (one pipe steam system) or two pipes at each radiator (one "in" and one "out" = two pipe steam heat system).

Also,

Watch out: when you moved a steam radiator you may have re-routed steam piping improperly, such as over a doorway or without maintaining proper slope. If you made that mistake condensate trapped in the piping can prevent the radiator from getting hot. - Daniel Friedman

Steam boiler shuts down after just a few minutes - broken steam vent?

Boiler works for a while ( 3 mins) and then shuts down. Surrounding pipes get very hot. Just discovered my steam vent might be a problem.

Just turned the small screw on top and now is hissing steam. Is the value possibly dirty and jammed preventing the radiators to warm up. On 2017-10-21 by bomahony -

Reply by (mod) -

Bom

I don't know what sort of safety equipment is installed on your steam boiler; some units may indeed use a temperature limit to shut down the boiler at unsafe heat levels.

I'd also look for spillage from a pressure relief valve and I'd check the system's operating pressure against it's specifications - residential steam heat typically runs at about 0.5 psi.

As the boiler is shutting down, a review of its safety controls would indeed be diagnostic. I can't offer more, knowing not a shred of information about your particular system.

Radiators won't get hot after new boiler installed

my heat gas boiler was replaced with a new one ---now all radiators dont get hot only when its first turned on...

throughout the day when it kicks on, not all radiators get hot or sections of the radiators get hot...i also get cracking, thumping ,sounds....

it kicks on like 5minutes then turns off , only the pipes going upstairs get hot ..radiators downstairs are mostly cold

my old boiler heated up all sections of every radiator and was quiet no noises at all - On 2016-12-24 by mike -

Reply by (mod) -

Mike

I'm flying blind here, Mike. Did a tech who knows steam install the boiler? For example a mistake with condensate return piping can cause trouble.

CHeck the pressure control switch: normally it's set between 0.2 and 0.5 psi. Not higher.

If the boiler is making steam and the steam riser at the boiler is hot but steam doesn't continue to rise, I suspect that a main steam trap or vent could have become clogged, maybe with crud stirred during boiler replacement or from the old boiler

. I'm guessing that direction because if it were steam vents on the individual radiators it'd be unusual for all of them to fail at once.

Follow the steam supply pipe to see where it changes from hot to cold - that could be diagnostic.

If you search InspectApedia for STEAM HEAT there are quite a few diagnosis and repair articles.

Also see the top of this page: STEAM HEAT RADIATOR REPAIR where we list hings to check.

 

Cause of cold steam radiators in two buildings traced to internal leak in steam boiler!

I have done all the things you suggest at STEAM HEAT RADIATOR REPAIR.

Pitched the radiator, changed the air valve, even putting a larger orifice air valve and removing the radiator to check the open and closed position of the supply valve.

I still get cold radiators. The larger steam supply valves are properly pitched in the basement and the boiler runs a sufficient amount of time to build up pressure. Is there anything else?? - Robert

More information:

This problem exists in both a private house and in a six family dwelling. Both have a one pipe system. In the private house, only the second fl rear (about 3 radiators) are cold. The radiators directly below are hot.

In the 6 family, both apartments on the 2nd fl are cold or get hot on one side only. - Robert

Reader Diagnosis: cold radiators traced to low boiler pressure caused condensate return line leaks

If anyone has this problem check for leaks, cracks or holes in the sections of the steam boiler.

Also check return lines for leaks.

It seems if fresh water is constantly being fed to the boiler, a corrosive reaction takes place in the sections of the boiler.

In this case there were leaks undetected in the return lines which caused water to be added constantly.

The fresh water ate at the sections in the chamber causing two small holes.

This in turn did not allow enough pressure to build up for steam to reach the radiators. After replacing boiler all radiators were very hot and also at a much faster rate. - Robert

Reply/comment:

Your cold steam radiator diagnosis success will add a helpful item to check and I'll add it into the diagnostic text above.

Indeed if your steam boiler is using more water than usual, I usually suspect a leak somewhere - often a small leak in a condensate line can go unnoticed; On occasion we also find excessive water consumption because radiator steam vent valves are not closing when they should (when the radiator is hot).

But I had forgotten that an internal leak in the boiler and that is going unnoticed and is large enough to prevent building up adequate steam pressure to heat the radiators can result in low boiler pressure, increased water use, and failure to deliver heat to upper floors.

And your reminder that abnormal water consumption increases corrosion in the boiler is very important since, as you explain, the result can be leaks in the boiler itself.

Unfortunately the good news of a correct diagnosis can lead to the bad news of a costly repair - the need for a replacement of the steam boiler.

We're always smarter in hindsight - and now I also see that your observation that lower radiators got hot but upper level radiators all did not, could have pointed to a steam pressure problem. Too often an amateur "fixes" the problem by trying to set up the steam pressure at the control switch - not the right approach.

Thank you again. We welcome and appreciate reader questions - it helps us find where to add or clarify our information. If in the future you do not receive a prompt reply to an urgent question left on a particular web page/article, just shoot me a personal email using the CONTACT information found at page top or bottom and I'll be sure to get to it. - Daniel

 

Only one room gets in one apartment heat when other radiators on all other apartments are working

I'm having the problem with radiator on first floor one room only getting heat to all other floors 4 in total 23 apartments checked vent valve tilt of radiator flushed the supply pipe back to boiler.

It's clear steam comes up to radiator but seems to just sputter out? (Feb 4, 2013) charles whalen

Reply:

First: replace any steam vents that are not working: if there is good pressure in the system and the radiator valve is open but no air vents out of the steam vent, I'd replace it as a easy, low-cost repair that often hits the spot.

Also look for a blocked or closed radiator valve valve or a radiator valve that is broken internally and also check for a steam vent that's not opening.

 

How to diagnose odor coming from a steam radiator

Months ago, when I used to turn the control in the upstairs closet off at night that controlled the boiler and the radiators in the house, all of a sudden one day I started having trouble turning on the control downstairs that controls the temperature.

It wouldn't come on, unless I would go back upstairs and turn the control switch off and on again. A repair man just told me not to turn it off anymore at night and put in a new thermostat upstairs. So I did what he said and stopped turning it off at night.

My friend I am staying with thought it made his bedroom hotter so that was why I turned the switch off at night in the upstairs closet where the boiler is located.

Now all of a sudden there has been a smell coming from the radiator in the kitchen. That is the new radiator that a company put in about a year ago, they removed the old one so we would have a larger radiator in the kitchen. This is completely different brand of radiator.

Then all of a sudden one day recently, I got up in the morning and the whole kitchen smelled just awful with that chemical smell.

Right as you walk through the door you would get a waft of it right up your nose,and the radiator is right there on the left as you walk in.

I just couldn't figure out what it was, and my friend and I thought it was the refrigerator giving out, so I bought a new one. But the smell was still there.

Finally I went upstairs and discovered that without me knowing it, my friend had turned off the heating control upstairs again in the closet where the boiler is.

So I turned it back on and moved the thermostat downstairs to start the heat a little bit then turned it down to where it clicked off.

The smell mostly went away but now I can still smell it a bit just as I walk into the kitchen so I leave the kitchen window open somewhat because I am worried about what the smell is.

Anyway, the people that put it in insist that smells cannot come from a radiator and will not do anything about it.

I think that maybe there is something that happens when it is turned off at where the boiler is in the upstairs closet and that this one radiator in the kitchen doesn't have whatever safety mechanism in it that all the other radiators in the house do, that would keep it from leaking whatever it is that it is leaking.

It was a special different company that put in the new kitchen, they reconstructed the whole thing, flooring, cabinets, countertops and so forth and had also put in that new radiator.

So what could this be... any ideas? And what can I do about it? I asked them if they could just remove the radiator and install another one like what was there before but they won't. They told me they would send out someone to flush out the System, but they did not ever do that. (June 11, 2016) Claudia Thompson

Reply: common causes of smells at a single, new steam radiator

Claudia

If you are absolutely sure the odor is coming from a specific radiator, look for

• a lubricant or sealant or chemical used to install the new (smelly) steam radiator or that was spilled on or near it during installation
• a spill of a chemical or cleaner anywhere near that new radiator that thus emits odor when the area is heated
• a leak at the radiator or its valve or vent
• something that spilled on, behind, or near the radiator
• a dead animal in the wall, floor, ceiling near the radiator
• an odor coming up through an opening through which radiator piping passes

Detailed advice for tracking down an odor source begins at ODORS GASES SMELLS, DIAGNOSIS & CURE - home

 

Steam radiator not getting hot, water in the line

Steam radiator not getting hot line changed in basement sloping upward before downward slope to furnace that section has water in it can that be the problem. (Oct 11, 2016) bob

Reply:

Agreed: an improperly-sloped steam supply or condensate return line can block the steam heat system.

You may need help from a plumber to adjust the condensate return line piping so that it slopes down towards the boiler.

 

How to to cut and cap an old steam radiator off; asbestos insulation worry.

I plan on removing a radiator in kitchen for various reasons.

There is a spot in the basement to cut pipe and cap.

However, there is some asbestos insulation I would love to avoid.

Is it possible to simply cap it where the intake valve is? Is that a norm? Same size? Thanks for any help. (Oct 25, 2016) David

Reply:

If you can remove the piping with insulation intact that will probably be the least-disturbance.

Yes you can cap off an un-used steam riser as long as it was feeding just that one radiator.

See this advice

• ASBESTOS REMOVAL, AMATEUR
• ASBESTOS REMOVAL CERTIFICATIONS
• ASBESTOS REMOVAL GUIDE, FLOORING
• ASBESTOS REMOVAL, WETTING GUIDELINES

...

...

Continue reading at STEAM HEAT RADIATOR REPAIR or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• RADIATOR STEAM VENTS
• STEAM RADIATOR PIPING CONNECTIONS
• COLD HEATING RADIATOR REPAIR (hot water / hydronic heat) if your heat is by hot water baseboard or radiator or convector rather than steam heat.

Suggested citation for this web page

COLD STEAM RADIATOR FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING RADIATORS

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