Steam radiator (C) Daniel FriedmanBanging Pipes & Radiators
How to cure banging, clanging, hammering pipes & radiators

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Steam & Hot Water Heating Pipe, Boiler or Radiator Noise Diagnosis & Repair:

This article explains the causes and cures of noisy or banging heating pipes and radiators in steam heat systems. We describe different noises made by heating steam or hot water heating systems, how to track the noise to its cause, & how to cure the problem.

We discuss the following: Banging Noises at the Steam Boiler, pipes, or radiators. Causes of noise problems in hot water and steam heating systems: air bubbling, banging, clanking, creaking, hissing sounds and what they mean, how they are fixed. How to shim the one pipe steam radiator to cure banging, clanging, pistol shot noises at the steam radiator.

Banging radiators, clanging heating pipes, bubbling noises, creaks, hisses, pops, and the like are diagnosed & fixed by these procedures.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Steam Heat Piping or Radiator Banging or Pounding Noise Diagnosis & Cure

Low water cutoff (C) Daniel FriedmanSteam Heat Piping or Radiator Banging or Pounding Noise Diagnosis & Cure

Article Contents

Categories of Noises Traced to Heating Equipment & Building Piping

Both steam and hot water heating system pipes can be a source of loud irritating noises in buildings: banging, creaking, and bubbling sounds may be traced to heat piping. Some of these sounds are just annoying, others can spell more serious trouble.

We divide banging or pounding pipe & radiator noises in building heating equipment & piping systems into these categories:

  1. STEAM RADIATOR NOISES: Banging or pounding noises at steam radiators are discussed right here - just below
  2. BANGING STEAM HEATING PIPES heard mostly on steam heating systems but occasionally (more creaking and cracking noises) on hot water heat systems as well are discussed in the article below
  3. Water hammer noises in house plumbing systems, typically water supply piping - discussed in a separate article
  4. Banging, creaking, hissing noises at hot water heating systems are discussed in a separate article beginning
  5. Banging popping noises in water heaters are discussed separately
  6. Banging pipe noises on hot water heating systems may be traced to sudden closing of zone valves or the starting & stopping of circulator pumps or backwards-installed zone valves.


Also see SOUND CONTROL for PLUMBING for an extensive list of causes and cures of building plumbing noises.

Also see NOISES COMING FROM WATER HEATER for the diagnosis and cure of clanking or thumping noises that may be coming from your water heater or heating boiler.

Noisy Banging Pounding Steam Radiators

Steam radiator (C) Daniel FriedmanSteam Radiators Sloped the Wrong Way Cause Banging Noises


A steam radiator whose low-end is opposite the entering steam pipe can cause steam condensate (water) to fail to flow properly back to the heating boiler.

Steam radiators, in particular one-pipe steam radiators, should slope towards the one steam pipe found entering one side of the radiator at its bottom. That is, the high end of the radiator should be at the opposite end as the end where the steam pipe enters.

Why does a radiator sloped the wrong way cause banging noises?

Condensate blocking the movement of steam through the radiator can cause a "hammering" or banging sound (sometimes described as a pounding noise) when steam pressure builds enough to break through this water blockage or "water dam" in the radiator bottom.

Our photo (above-left) shows a one pipe steam radiator that was shimmed at its "high" end - the end that includes the steam vent. Notice the small wooden square shims? Some people use a metal washer or coins in this location. You can see the one pipe entering at the radiator bottom right.

So Should I Level the Radiator to Stop Banging Noises?

No. A steam radiator needs to pitch slightly downwards towards the end that connects to its condensate return line.

Watch out: some "banging clanging radiator noise" repair articles we've read advise that you should fix a banging hammring radiator by making sure it's level. For steam radiators, devices that need to return condensate to the boiler, that's incorrect, as we explain here.

How to add shims under the radiator at the end that should be high: You may be able to cure this radiator noise source or even fix a radiator that doesn't get hot simply by installing shims under the end of the radiator that needs to be raised so that there is just a little slope towards the steam pipe. You don't need an excessive amount of slope, just enough that any condensate in the radiator bottom will drain towards the outlet or steam pipe.

Try placing a level on the radiator top and take a look at the radiator's slope. Shim the end of the radiator opposite the steam pipe so that it is just elevated higher than the steam pipe end.

Your heating service technician should be someone familiar with steam heating systems and the proper layout and function of condensate return lines in your home. The tech will look for a problem that is blocking condensate return to the heating boiler, such as a clogged strainer in the system piping, a steam trap clogged with rust, minerals, or sediment, or a similar problem.

Other Causes of Banging, Clanging or Pounding Noises at Steam Radiators

A separate problem: failure of individual steam radiators to get hot, could also be due to blocked condensate return.

If a radiator's steam vent is not working, or if a one-pipe steam system's radiator has settled so that it is no longer properly tipped to send condensate back into the steam pipe (and back to the boiler), that radiator will stop working. Individual radiator heating troubles can explain banging or pounding noises.

Details about steam radiators that are not warming up are

Watch out: If your heating boiler does not have an automatic water feeder and you've been putting makeup water into the boiler manually, a blocked condensate line and low water in the boiler will eventually lead to total loss of heat when the low water cutoff switch
(see LOW WATER CUTOFF CONTROLS) , a key boiler safety device, simply shuts down the boiler.

Avoid this Bad Advice about Steam Pressure Adjustments

Watch out: we noticed some "how to" articles on steam heat at other websites that advise homeowners to adjust the steam heating system pressure by adjusting the water fill valve on the steam heating boiler or by draining water out of the boiler. That incorrect advice could cause heating system malfunction or loss of heat or damage to the equipment!

Drain valves on heating boilers, hot water or steam, are not pressure control devices.

Air bleeder valves found on hot water radiators (not steam radiators) are opened to bleed air out of an airbound hot water radiator, but are certainly not pressure control devices.

On a steam heating system the pressure is controlled by a pressure control device:

Typically residential steam pressure is less than 1 psi (low pressure steam systems).

If we see that someone has set pressure higher than that on a residential steam boiler we suspect someone was trying to "force" steam heat to rise in a system where there are actually problems with radiators, steam vents, or steam piping. Consult with an experienced steam heat technician, and don't change your steam boiler pressure on your own.

On a steam boiler makeup water is needed frequently as steam heat systems always consume some water. Makeup water is provided either manually by a fill valve, using a sight glass,
see SIGHT GLASS, STEAM BOILER, on the steam boiler,

or more often by an automatic water feeder

Consult with an experienced steam heat technician if you are not sure how your boiler's makeup water is provided.

Banging Hammering Steam Heating Pipe Noises: Causes, Cures

If it sounds as if someone is down in your basement or cellar banging on the heating pipes with a hammer, and particularly if your building is heated with steam radiators, the noise you hear may be due to water hammer in the steam piping system. Other terms we hear from readers describe this problem on steam heating systems as

All of these noises may be due to the same steam heating system problems, as we explain here. Different heating system noises occur on hot water heating system pipes and radiators (hydronic heating systems): creaking or air bubbling - also discussed here.

In both one-pipe and two-pipe steam heat systems steam rises into the building's heating radiators, forcing air out of the radiator's steam vent , then making the radiator hot. Inside the hot radiator steam condenses back to water as heat is radiated (by the "radiator") into the room -

This steam condensate must drain back into the steam boiler where it is subsequently re-heated to steam to continue the heating cycle. But if the condensate is having trouble returning to the steam boiler your heating pipes may become waterlogged.

This happens because when the steam boiler water level drops and is not replenished by returning condensate, the automatic water feeder will just send more water into the boiler.

Condensate accumulating in the steam piping (when it should be returning to the boiler) not only water-logs the system, it also means that cooler condensate (water) comes into contact with hotter rising steam in the piping. This contact can cause rapid expansion/contraction in the heating pipes and produces the loud "pipe banging" noise we are discussing.

Banging Steam Pipes Caused by Improper Slope

Steam pipes themselves, particularly in a one-pipe steam system, are designed to slope continuously back to the boiler from every steam radiator. Sometimes in an older home with one-pipe steam heating someone changes or relocates a steam pipe for convenience or remodeling, or building settlement causes pipes to lose their proper slope.

Typically the steam pipes on an individual floor will slope about one inch from high to low point, assuring that condensate can drain back to the steam boiler. If your pipes have lost slope, condensate blockage in the piping can cause the same banging or horrible pistol shot sounds that we described above at our discussion of steam radiators.

Banging steam heat pipes are usually heard at the beginning of the heating cycle.

Banging heating pipes that are heard at the end of the steam heating cycle may mean that the steam heat system pressure is incorrectly set or that a condensate return line near the boiler has become clogged.

A partly closed gate valve or a valve whose internal components are broken could also be the cause of this noise. We check to be sure that our steam radiator valves are fully open as part of diagnosing this noise. In an emergency it may be possible to temporarily diagnose or even temp-fix this radiator valve problem by turning off the heat, and when the system is cool, open the gate valve to remove the valve's bottom component that actually closes the valve, replacing the remaining components to leave this valve "fully open".

Other writers assert out that air trapped in steam pipes can also cause banging noises. Air in the steam piping and radiators should be venting out of the steam system through the system main line and individual radiator steam vents as the system is heating up during each heating cycle.

Banging Steam Pipes or Radiators - Check the Radiator Valves

If the steam radiator valve has been partly closed in an attempt to regulate the heat output of the steam radiator, that can cause banging as condensate may become trapped in the valve body. Try opening the valve fully.

You can regulate heat among steam radiators using a different method: timing how quickly individual radiators get hot, using adjustable steam radiator vents.


A second cause of banging steam pipe or radiator noises can be a worn or damaged radiator valve seat. Your heating service technician can remove, disassemble, inspect, and replace the valve or valve parts if necessary.

A third radiator valve problem is actually broken parts: Sometimes we find that the valve internal parts are actually broken inside, perhaps by someone forcing a valve that was corroded into a stuck position.

Watch out: a valve stem can become broken and fool you. You may feel that the valve knob turns and you think you are opening or closing the valve, but actually the valve knob and stem are just spinning freely.

Steam Vent Hissing

Hissing sounds from the steam radiator's steam vent are normal as heat is rising in the building, but the hissing should stop when the radiator is hot. See these steam vent articles for details:  

Banging Noises at the Steam Boiler: diagnosis & cure

Low water cutoff (C) Daniel Friedman

Banging noises at the steam boiler may be occurring in the steam boiler itself or in its controls, especially if the boiler is not being properly maintained.

Sludge that accumulates in the boiler and/or in the boiler low water cutoff switch (a critical safety control) needs to be flushed out of the boiler periodically. Typically the low water cutoff control includes a drain valve that is opened weekly to spill hot dirty sludgy water into a bucket.

Example Recording of Banging Noise at a Steam Radiator

Here is a RECORDING OF BANGING PIPES at a STEAM BOILER [2MB .m4a sound file recoreded 2015/11/29] provided by a reader whose comments follow. Play this file with iTunes or Quicktime or Windows Media player.

Reader Question: wierd banging sound, metal on metal, coming from our steam boiler

2015/12/01 Brad said:

About a week or so ago, we discovered a weird banging sound that sounds like metal on metal coming from our steam boiler. Sure, we get lots of small bangs in the pipes throughout the house, which we had always assumed to be just air in the pipes.

But this sound is different. It doesn't come from the pipes--it seems to be just in the unit in the basement. It only makes the noise when the boiler fires up and the flames turn on. The sound is always louder in the beginning, and it gets slightly quieter over the following minutes.

The speed varies--sometimes it is an irregular rhythm, and sometimes it is very steady. The banging goes off when the flames turn off. The banging appears to be coming from one specific corner of the unit. I'm worried that it is a pump or fan of some sort. I took a video in one of the quieter moments and uploaded it to Youtube [... link omittted here ] just in case it helps


Often steam boiler noises showing up as banging pipes or radiators are traced to a condensate return problem.

Please take a look at the suggestions on this page. If the boiler has at least a few years of previously soundless operation and the banging / clanking at the boiler is recent I suspect that the horizontal portion of the condensate return or steam supply line is debris-clogged.

Ask your heating service technician to take a look at the system.

Watch out: ask your heating service technician to show you when and how to safely flush the steam boiler.

Failure to perform this step can lead to loss of heat; doing it wrong can lead to scalding or even boiler damage. Details are

Watch out: If your heating boiler does not have an automatic water feeder and you've been putting makeup water into the boiler manually, a blocked condensate line and low water in the boiler will eventually lead to total loss of heat when the low water cutoff switch , a key boiler safety device, simply shuts down the boiler.

Other causes of heating system noises are discussed

Creaking Clanking Hot Water Heating Pipe Noise Diagnosis & Cure

Hot water heating pipes that distribute heat through a building often make creaking or even clanking sounds at the start and again at the end of a heating cycle.

These sounds are usually due to expansion of the piping and movements as the piping shifts, especially where it passes through an opening in building framing, floors, or walls.

Clanking heating system pipes or sharp snapping noises may be heard as a normal consequence of expansion of metals during the heating cycle.

These noises can often be eliminated or reduced by careful routing of piping and by allowing room around heating pipes for expansion, but probably not eliminated in the case of hot water baseboards.

Often we can eliminate these sounds by these steps:

Bubbling Sounds from Hot Water Heating Pipes: Diagnosis & Cure

Bubbling or rumbling heating system noises in hot water heating piping can be caused by air in the heating lines.

If the amount of air becomes excessive the heating system may be unable to circulate hot water and extra steps to bleed unwanted air will be required.

See these articles on how we get rid of unwanted air in a hot water heating system:


Continue reading at WATER HEATER NOISE DIAGNOSIS, CURE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BANGING HEATING PIPE RADIATOR FAQs - questions & answers about heating system noises, posted originally at this page.

Or see BANGING HEATING ZONE VALVES - noises in heating pipes traced to zone valves

Or see WATER HAMMER NOISE DIAGNOSE & CURE for other banging pipe noise diagnosis help.

Suggested citation for this web page

BANGING HEATING PIPES RADIATORS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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