# Hissing Noise From Refrigerant Line



## BayouRunner (Feb 5, 2016)

I would say it's normal if it's touching the wall. If you can find a way to move it away from the wall it should eliminate the problem. Sounds like you have bigger problems though if the unit was almost empty and the leak was not repaired.


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## supers05 (May 23, 2015)

Gurgling is normal at first, but is a sign of low refrigerant if it continues non-stop. The hissing can be a leak or just a vibration being transmitted, hard to say over the internet. 

That leak really should be repaired though. 

Cheers!


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## dcny6923 (May 8, 2016)

Thank you for the replies. Could the hissing sound be the sound of gas escaping the little copper pipe? 

It's loud enough that I hear it upon entering the room about 20 feet away.

If there was low freon to begin with, would the same hissing noises come?


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## BayouRunner (Feb 5, 2016)

The noise you are hearing is the refrigerant moving through the pipe. The line could be touching the wall. Could be touching the brick and transferring the noise to the wall. Could be air in the lines causing high head pressure. There is a lot of things that could cause it. I'm assuming low in gas is not causing it because the unit was just charged. If you had that big of a leak in the wall the unit would most likely not be cooling already. It's rare to have a leak in the wall but when it happens it's usually caused by some type of construction, picture hanging lol etc


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## roughneck (Nov 28, 2014)

Hissing can happen even with normal operation, it's not a sign that anything is or isn't wrong. 
If the unit was low on refrigerant, and no leak was found or repaired, then you will have the same problem again. Refrigerant is not a consumable material, and doesn't need "fill ups". If the charge was incorrect then either it was charged wrong from the start, someone's letting it out or there's a leak.


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## yuri (Nov 29, 2008)

The little line is a liquid line and full of liquid refrigerant. It actually sounds like water running. Probably it is touching the wall. If it had a huge leak large enough to hiss then it would leak out in half an hour or less and you would have no cooling.


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## rjniles (Feb 5, 2007)

A leak in the line set would hiss even if you shut down the system (at least until the refrigerant is gone). Don't ask me how I know but it cost me $296.


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## supers05 (May 23, 2015)

I agree, if you could hear it through the wall, 20ft away, it isn't a small leak. The wall would likely be cold until the hissing stopped, and you'd be out of refrigerant already. Yes, it "could" be the leak you're looking for, but highly unlikely. If you're still cooling, then it's a much smaller leak, likely one that you can't hear. 

Cheers!


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## dcny6923 (May 8, 2016)

Thank you everyone, the comments make a lot of sense. 

I didn't think of the fact that if it was a leak then it would be continuous, but the hissing is only present with the ac is on. 

16 hours later, the unit is still cooling. I went up to the attic and the noise is there too but much less pronounced. Behind my bedroom wall thought it is the loudest (and this spot happens to be right behind my pillow, sigh) 

Since this noise wasn't there before the freon was added, does the loudness of hissing have a positive correlation with the amount of freon injected to the system? Meaning the more that is added the louder the hiss would be, and vice versa. 

I'm just thinking if the contractor added more to the system than he was supposed to.


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## user_12345a (Nov 23, 2014)

Water flowing sound is healthy and yes higher pressure or higher volume will make the noise more noticeable.

if you hear variations in the sound like gurgling, air bubbles etc there's an issue, granted lots of systems ma have that and cool fine.


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