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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.
Banging radiators, clanging heating pipes, bubbling noises, creaks, hisses, pops, and the like are diagnosed & fixed by these procedures.
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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:
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.
Steam Radiators Sloped the Wrong Way Cause Banging Noises
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.
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
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 (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: see Pressure & Temperature Settings, Controls. 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 (SIGHT GLASS, STEAM BOILER) on the steam boiler,
or more often by an automatic water feeder (WATER FEEDER VALVE, STEAM).
Consult with an experienced steam heat technician if you are not sure how your boiler's makeup water is provided.
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 (see STEAM HEATING SYSTEMS), 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 (see STEAM VENTS), 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.
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.
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.
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:
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.
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 (see LOW WATER CUTOFF CONTROLS) , a key boiler safety device, simply shuts down the boiler.
Other causes of heating system noises are discussed
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 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 the More Reading links shown below.
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Frequently Asked Questions (FAQs)
Question: sound at steam radiators in off position
(May 19, 2011) dave said:
I want asking about if have sound air/steam in my heating radiator and a little bit warm eventhough on the position turn off ? What i must to do if like that? Thank you for your help.
If your steam radiator is turned "off" at its local radiator valve but it is still getting warm, then the radiator valve is not fully closed. It may be that the valve needs to be replaced.
If your steam radiator valve is turned "on" and gets warm normally but the steam vent on the radiator never stops hissing at all during the heating cycle, then the steam vent itself may need replacement - a simple and inexpensive repair.
Question: slapping sound at heat pump
(Dec 5, 2011) carolyn garza said:
Our heat pump makes a loud slapping sound at various times. I don't think it makes this noise when the motor is on.
Question: towel radiator needs bleeding
(Jan 12, 2012) Robert Hobson said:
We have one towel rail radiator and water tank heated from a stove back boiler. The radiator needs bleeding every time we heat the water up and switch on the pump. Could we fit an automatic bleed valve to the towl rail to cure this?
Probably but why not give the manufacturer a call to ask them. They may suggest a strategic vent location that is upstream from the towel radiator.
Question: Crown boiler air purger not needed?
(Feb 2, 2012) Peter Kurtenbach said:
I have just had a new CROWN TWZ065 boiler instaled.
Removing an air purge is ok IF there is another adequate air purge in the system such that you're not leaving an air trap
Question: house is too hot after changing a leaky valve on a gas boiler
(Feb 4, 2012) Tony Caputo said:
I have a gas hot water boiler. Recently I changed a leaky valve. I then bleed the system and put it back on.
I suspect that a zone check valve is stuck open
(Oct 23, 2012) David Bala said:
Banging radiators are discussed above.
(Nov 9, 2012) Prudence said:
Cape Code style home built 1950's- 1 pipe system- exactly as shown above. 1 1/2 years ago new boiler/burner and pipes to and from boiler/burner to radiator(s) pipes replaced. New bleeder valves ( left in open position) installed on radiators. 1st season( last year) all appears fine, until end of season when loud bangs could be heard. Shortly thereafter, heat was off for summer. No seperate hot water heater- burner ran over summer only for hot water. No banging to be heard. Recently turned heat on. Within 10 minutes heat coming from radiators and LOUD banging began. Turned off thermostat. Hour later turned heat on, In attempting to pinpont location of bangs,observed water flowing down basement wall, at point beneath an upstairs radiator. Turne off thermostat- checked water level in glass tube = full and dirty. 1st plumber drained bolier, water level back to 1/2 mark.
Approx 6 minutes later, all appeared ok. Plumber left. Within few short minutes discovered water spewing out from bleeder/seeping from pipe (leading into radiator-see photo above: pipe bottom right-from floor into radiator ) on radiator located above where water was discovered flowing down wall in basement. Turned off thermostat- called plumber who advised I seek steam experienced plumber. Next day, with thermostat off, water tube was again, filled to top- water clean in appearance. Next plumber came in, again drained boiler until water in tube was at 1/2 way mark. Without turning heat on, plumber's assesment is pipes from burner/boiler to radiators are not angled correctly. Advises pipes be removed and reinstalled at correct angle. States job is very labor intensive.
Question. If plumber is correct, culprit = current position of pipes, why issue now and not last season? Desperate for assistance. Fearful to turn heat on and very cold here= fearful of pipes freezing. Extreme difficulty in finding experienced steam heat plumber. Any and all suggestions greatly appreciated!
Prudence, you might search InspectApedia for "Banging radiator pipes" or Banging Steam Pipes = for more diagnostic details; in general I suspect a condensate return problem. Indeed if the boiler changeout changed the slope of a condensate return pipe ANYWHERE in the system that will often cause a condensate return blockage - condensate needs to return to the boiler by gravity.
If your plumber can point to improperly sloped pipes it sounds to me as if s/he's on to the problem and probably knows more than either of us.
(Feb 13, 2014) Anonymous said:
i have a water automatic feeder.but in the morning is goes up about more than 3 times.it gets to the point that feed all away up.than after couple of days it bangs so much especially in the morning. i have to drain so much water in order to quite dawn. i called a plummer is telling me to avoid the noice. but i cant helped it makes to much noise that even water had come out. they said that the water feeder is ok. who could help me
Sept 26 2014 Patricia Kimball said:
Within the last 3 months our copper pipes makes a loud banging when the furnace pumps hot water thru the pipes. Tried draining, didn't help. Have a filtration system that doesn't seem to be involved. For 18 yrs. there was no problem--no recent alterations to the system. Would appreciate any suggestions.
Banging steam pipes, discussed in the article above give some clues, Patricia, but I'd add that we need to ask what has changed. Even if the system has not been knowingly altered, rust and crud in condensate system piping can clog a return, for example.
Also see RADIATOR VALVES & HEAT CONTROLS
Question: banging copper pipes when the furnace pumps hot water thru pipes
(Sept 25, 2014) Patricia Kimball said:
Look for blocked condensate return or radiators sloped the wrong way.
Question: loud banging pipes when the heat kicks in - can I insulate the radiators to control the noise?
(Oct 3, 2014) Emma said:
I am doubtful that insulating steam heat radiators or piping is going to be a happy solution to banging pipes - as it risks interfering with heat transmission; more likely what's needed as a steam heat tech to diagnose and fix the banging pipe cause.
Question: Boston building: what's the role of the condensate reutrn
(Nov 4, 2014) Luiz G said:
Condensate in a steam heat system returns to the boiler to be heated again into steam to provide more heat. If we didn't get rid of condensate from the radiators they'd all stay cold as water would prevent steam entry; if we didn't return condensate to the boiler it'd use more water than necessary, speeding boiler corrosion, reducing boiler life.
Luis the condensate returns to the boiler to be re-heated to make more steam. If no condensate returned but say were dumped into a drain the boiler's water usage rate would skyrocket as would the heating cost while the life expectancy of the boiler would diminish.
Question: loud heating pangs in Marshfield Wi - wiring question?
(Nov 6, 2014) Adarious said:
Every time the heat comes on, within a minute loud pangs and sometimes rapid not-so-loud (like a cooling car radiator but louder) sounds come from the area of the radiators themselves. The landlord is an aged man and whenever I have brought up things that need to be done (such as better breakers) I get told to do it. That said, what options can you suggest in order to alleviate such loud noise? I live on a fixed budget, so I cannot afford expensive remedies, but I would like to be able to do something about this.
15A circuit breakers would normally be paired with #14 gauge copper electrical wiring. #12 copper wire (which would be fine) would support a 20A circuit.
Of course if your wiring were aluminum then the rules change and you'd see #12 aluminum wire on a 15A circuit.
That has nothign to do of course with banging noises. Our best advice on reducing banging radiators and pipes is in the article above.
(Dec 4, 2014) Martin said:
Martin do any of the banging pipe explanations in the article above suggest help for your system?
If not, tell me what's changed since before the banging.
Question: can't turn off the heat
(Dec 16, 2014) Fiona said:
By installing a thermostatically operated radiator valve every radiator can be individually controlled to regulate room tempeature;
Question: moaning whining noise from the cellar
(Jan 7, 2015) Annie Keller said:
The whining is coming from the cellar - from the actual boiler itself, not from individual radiators in the house. The whining only happens when the temp outside gets to a certain low and the colder it is outside, the more and louder the boiler whines. Not sure how individually regulating radiators would solve the problem in the cellar. The radiators themselves are working perfectly fine. Is there such a thing as boiler insulation or a boiler cover to keep the boiler from frigid temperatures in the cellar? It's an unfinished cellar with no heat. Thanks for your response ahead of time....
21 Feb 15 susan said:
Question: loud banging noise 15 minutes after the thermostat kicks the boiler
26 Feb 15 Cathy said:
We discuss the typical causes of banging steam pipes in the article above. I don't have better suggestions; your plumber is doubtless correct: the problem can be fixed given correct diagnosis. Usually people start by looking for a blocked condensate return.
Questions & answers or comments about troubleshooting noises in steam heating system pipes or radiators: hissing, banging, creaking, clanging.
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