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Refrigeration gauge set (C) D FriedmanRefrigerant piping gurgling noise
Diagnose running water or burbling sounds in air conditioner or heat pump systems or in any refrigerant piping

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How to diagnose running water sounds in refrigerant piping at the air conditioner, heat pump, or refrigerator:

What causes running water sounds or burbling or gurgling noises heard in the refrigerant piping or tubing in an air conditioning or heat pump system? Gurgling noises in HVAC or refrigeration equipment is often traced to an improper refrigerant charge, refrigerant gases in the liquid refrigerant line.

Air conditioner or heat pump noise diagnosis & cure: this air conditioning repair article series discusses the diagnosis and repair of air conditioning compressor noises which range in importance from normal (if annoying squeaks and squeals, to rattling loose bolts and hardware, to costly compressor damage indicating air conditioning compressor or A/C compressors at or near end of their life.



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Running Water Sounds in Refrigerant Piping, Compressor, Air Handler may sound like flowing water or gurgling

Refrigerant floodback noises - running water or gurgling sounds in the refrigeration piping

Reader Question: I have a 4 ton heat pump that hisses when it shuts down in 40* weather. The frig. lines run in the wall near bedroom. Sounds like freon running back to or from compressor, Only in heat cycle. - richdunegan@gamil.com 12/11/11

Question: Just this morning I noticed when my heat unit/pump was running it sound as if water was draining through pipes. (The out side connections to the pump/inside unit run over head in my laundry room) So far there's been no other issues. Any idea what this could be? Should I be concerned? Once the heat shuts off this draining sound quits. - Ruth 1/25/12

Question: I live in a 1st floor apartment. When the A/C of the resident on the 2nd floor turns on, there is a sound like cascading water in about 1 minute intervals and lasts for 15 seconds or so. This continues under the unit turns off. I have been told by maintenance that it's the freon rushing through the pipe and that it's normal. I have lived in several apartments and have never heard this before. Invariably, for some reason, condenser units are always just outside bedroom windows. lol
So, my question is, is this indeed normal? - Anonymous 2016/06/27 by private email

Reply: causes of running water, bubbling sounds or burbling gurgling noises in HVAC equipment

  1. Under-charged refrigerant or a problem originating at the condenser/compressor might cause running water sounds in the high pressure refrigerant line on an HVACR system, though usually complaints are traced to these second condition we state next.
    See UNDER CHARGED REFRIGERANT, EFFECTS for more details.

Bubbling in the refrigerant piping is discussed at REFRIGERANT LEAK REPAIR and may indicate a refrigerant leak, though bubbling sounds on split systems at the indoor wall unit may be normal for some products.

  1. Refrigerant floodback noise can occur at any time not just at startup. Floodback noises are likely to be heard in the suction line of the HVACR system.

Running water sounds, bubbling, burbling, gurgling noises in the air conditioning or refrigeration system suction line may be due to liquid refrigerant in the suction line on the low-pressure side of the system. Floodback happens in the suction line when liquid refrigerant is burbling along where we expect to find only refrigerant in a gas state. That might be caused by a problem with the refrigerant metering device or by an HVACR system that has been overcharged - too much refrigerant has been added to the system.

Watch out: A severely overcharged system compressor can have floodback when running and this can lead to compressor failure from oil being flushed from compressor or broken valves in reciprocal compressors. - Tommy 1/15/2012

  1. Equalizing refrigerant pressures at shut down or at a heat pump when the reversing valve operates or when the system reverses direction for defrost during a heating cycle can cause whooshing sounds that are normal. But at this point you may also hear gurgling or bubbling sounds - in that case check for low refrigerant.

Ruth,

Also check for running water sounds traced to drain piping that receives air conditioner or heat pump condensate from a condensate pump. Because the condensate pump only runs when its reservoir is filled, the pump on-off cycle will be irregular, but the pump may be sending water into a building drain that, because of its material (plastic) and location (not through sound-insulated space) could show up as a running water or gurgling sound.

Anonymous: "Normal" to some techs is "problem" to others - it depends on exactly what's going on.

For example, insufficient charge of refrigerant or air contaminants in the system can cause one to hear refrigerant burbling along in the high pressure line where normally the line is full and silent. If my guess is right, ultimately the 2nd floor resident will have no cooling and the system will have to be repaired properly.

Reader follow-up: evacuate and re-charge the system with refrigerant?

Question. Would evacuating and recharging the system be a course of action? And is this an expensive process? Or is the way to look at it do this and you won't have to replace the compressor?

Reply: fix the refrigerant leak, install the factory-specified volume of refrigerant charge

Yes. And yes. But the cost to properly charge an HVACR system is certainly significantly less than wholesale replacement of the compressor/condenser. I'm unclear on why someone has suggested that compressor replacement is needed for this problem.

Keep in mind that anybody diagnosing a complex system by e-text is unable to see onsite clues that would shout loudly to any competent expert who is on-site.

Assuring that the system is properly charged is a step techs take to address the running water sound problem we're discussing as would be appropriate for a low refrigerant charge for any reason. Some HVACR systems include a sight glass on the refrigerant line that allows the tech to actually see the refrigerant gas bubbles but most residential systems don't.

Returning to the question of refrigerant charge vs. running water sounds in the piping:

A tech who's trying to guess at the refrigerant charge on a running system will measure temperatures on the high and low lines, but all that tells you is that there is enough refrigerant to cool the coil, not that the full measured charge called for by the manufacturer has been placed into the system.

It's an expensive and low quality but very common repair to simply add enough refrigerant to get the system cooling. That is very likely to be less than the charge volume specified by the manufacturer (and profitable for the service company). If there is an ongoing refrigerant leak, the system will ultimately stop cooling again, perhaps first icing the coil then stopping cooling entirely.

A proper and best repair when the refrigerant charge is low is to find and fix the refrigerant leak, then place a proper charge in the system, charging with the quantity of refrigerant specified by the manufacturer. Most HVACR systems other than very small ones include a receiver that buffers a charge of refrigerant that is larger than simply the bare minimum needed to fill the tubing and compressor.

Question: running fluid noise in the pipes after the fan stops: refrigeration pipe gurgling sound

(Aug 31, 2015) john stanaway said:
The air sending unit continues to make a running fluid noise in the pipes after the fan shuts. The weird thing is that a loud noise will stop the running water noise in the air sending unit. It makes no sense. When I yell "stop" it stops if not the water sound in the pipes continues. Any ideas? 520-302-9990 John

Reply:

John:

Maybe we can hire you to get some other annoying things to stop by shouting at them - sounds remarkable!

I'm guessing there is gas in the refrigerant piping OR condensate drain water noise. See if you can pinpoint the source

More gurgling sounds that are also described as "running water noise" are described at GURGLING SOUNDS from the AC or refrigerant piping

Question: water rushing sound from neighbour's A/C system

Just wanted to update you on the water rushing sound when my neighbors A/C is running.

The property manager had a heating and cooling contractor look into this and he concluded that the problem is how the lines were run during construction. There are three sets of lines running through the foundation just below the outside wall. That outside wall is my bedroom wall. He did check the freon and found it to be correctly serviced.
So that's it. They say it's not financially feasible to repair. I want to thank you again for your time and help. - by private email from Paul Murnane 2016/07/17

Reply:

Thanks for the update. I'm disappointed, though and I'm not confident in that "checked the freon" step. An A/C unit may continue to cool with improper refrigerant charge - for a while. While of course there may be a design or condition about which I'm uninformed, in normal A/C systems properly set-up, there are no "running water sounds" in the refrigerant piping. The high pressure line from compressor/condenser to the refrigerant metering device at the cooling coil is filled with liquid refrigerant. Filled. The suction line on the outlet end of the cooling coil is filled with low pressure gas. Filled.

Running water sounds in refrigerant piping might come from:

Sooner or later this noise chicken will come home to cackle (or roost) as gas bubbles in the liquid refrigerant line probably mean an undercharge and perhaps a refrigerant leak that ultimately means the system will stop cooling. If you and I are still around I hope you'll let me know when that happens.

Reader follow-up:

Question. Would evacuating and recharging the system be a course of action? And is this an expensive process? Or is the way to look at it do this and you won't have to replace the compressor? - Paul Murnane

Moderator reply:

Yes. Keep in mind that anybody diagnosing a complex system by e-text is unable to see onsite clues that would shout loudly to any competent expert who is on-site.

But generally assuring that the system is properly charged is a step techs take to address the problem we're discussing. Some HVACR systems include a sight glass on the refrigerant line that allows the tech to actually see the refrigerant gas bubbles but most residential systems don't.

A tech who's trying to guess at the refrigerant charge on a running system will measure temperatures on the high and low lines, but all that tells you is that there is enough refrigerant to cool the coil, not that the full measured charge called for by the manufacturer has been placed into the system.

It's an expensive and low quality but very common repair to simply add enough refrigerant to get the system cooling. That is very likely to be less than the charge volume specified by the manufacturer (and profitable for the service company). If there is an ongoing refrigerant leak, the system will ultimately stop cooling again, perhaps first icing the coil then stopping cooling entirely.

Reader follow-up:

I've convinced my property manager to get yet another contractor to come address this. The intent is get someone to evacuate and service the system. Hopefully, they'll really fix what cause the problem in the first place. She told me that I could have you come and access the situation. I sure wish you could! But I told her that wasn't possible.
She did ask about you as far as your credentials. I didn't recall for sure, but I knew you had years of experience.
I'll keep you advised.

2016/07/22 My latest update. Maintenance supervisor says he evacuated system and serviced it. He says he did this Wednesday. Odd thing. I was home all day and the Property manager gave me a heads up that he would be doing the work that morning and I didn't see anyone that day around the condenser in question.

Refrigerant recovery & charging System - at InspectApedia.com 2016I was wondering if you would be kind enough to provide a list of equipment needed to perform this task. I know you have to have something to capture the old freon, right? And you need a pump to suction the system.

And if I recall it's usually a good practice to leave it in a vacuum to check if you have a change in your gauges over a two hour period which if you did meant you had a leak. Anyway. if you could do this, it'd be nice. Of course I would understand if that's not in your realm. I can research it and come up with the info. - Paul Murnane

Moderator reply: equipment needed to evacuate and then properly charge an HVACR refrigerant system

As we state at REFRIGERANT LEAK REPAIR, SAE J-2788, requires that

... all service equipment manufactured after December 31, 2007, must recover 95% of the refrigerant and recharge to within 1/2 ounce

To put a *measured* or "factory-specified" refrigerant charge into an HVACR system the system has to be evacuated - as you say. TO do that in compliance with current codes, the tech has to hook up a pump that removes refrigerant and pushes it into a storage cylinder (presumably for later recycling) as we no longer discharge refrigerant to the atmosphere.

In the old "destroy the earth" days we used to dump refrigerant to the atmosphere, run a vacuum to remove air from the system, possibly install a new filter-drier on the system to remove any remaining (and troublesome) moisture when the system was to return to operation, and then use a can of refrigerant and a charging cylinder to install the new measured charge.

Currently that job is typically handled by a wheeled kit that includes the vacuum pump, hoses, gas recovery and gas charging cylinders. It's not something that fits in someone's back pocket un-noticed. Below I copy in a typical example photo though there are both larger and smaller versions of this machine.

The pump is typically connected to the service fittings (Hi and Lo port connections) on the compressor/condenser unit outdoors.

Similar equipment is then used to place a measured charge into the system. Yes good procedure would be to leave a vacuum for 24 hours to check for leaks; not every tech might do that, however.

Watch out: Incidentally a second source of bubbling sounds heard in the refrigerant piping suction line near the compressor could be refrigerant oil pooling in that location. However for in your case a refrigerant oil pooling problem does not sound like the noise source that you have been describing.

More information on charging refrigerants in an air conditioner, heat pump, or other refrigeration equipment is at REFRIGERANT CHARGING PROCEDURE

Article Series Contents

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Continue reading at HVAC NOISE Group 4 or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see NOISES, HVAC SYSTEM DIAGNOSIS - home

Or see HVAC SYSTEM NOISE DIAGNOSIS FAQs

Or see REFRIGERANT CHARGING PROCEDURE

Or see SOUNDS of RUNNING / DRIPPING WATER in DRAINS - for running water sounds traced to a building plumbing drain system

Or see UNDER CHARGED REFRIGERANT, EFFECTS

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