Air Conditioning - Water Rushing Sound When A/C Kicks On

I have central air and two units outside. As soon as the lower AC unit comes on, I can hear a sound like rushing water going through the pipes somewhere above me. I keep hearing the water rushing sound every now and then while it's running and as soon as the unit stops, so does the water rushing sound. I've looked on other sites and they are suggesting that it could be a sign of air in my lines. Does this seem right? And if so, how do I go about getting air out of my lines? Can I do this myself (i.e. someone with no experience) or will I have to call a professional? Is it pricey? Thanks much in advance.

Sounds like the lineset (pipes between inside and outside) are to close to wood and resonating.

If this started a short time ago, could also be a first sign of low charge.

No air in the lines, that would be plumbing.

No you can't fix this yourself.

Call a tech and have charge checked.

Also you might have just been catching it at the right time. By that I mean, did the cycle end a short time ago and the pressures not equalize. Due to outdoor temps the refrigerant may be hanging out "indoors" when not in use too.

Thanks for the help. This problem did in fact start just a short time ago. I have also had a slow freon leak over the past couple of years with this particular unit as well. It seems I need the freon filled about once a year and it's getting about that time.

Could you tell me more about what a low charge is and what effects a low charge can have on an air conditioner? When I do call a tech, what are they going to do to fix the low charge?

First you have to be EPA to work on the freon in the unit. You can have any air in the lines. You said leak so there you go. Low on freon . So if the unit has a TXV in it you hear it open and close and the unit dont have all the freon it needs. low on freon your coil will start to ice up and no air can blow through it. Also bad to run a unit low on freon.;) GET THAT LEAK FIXED

Hello there!

Low charge simply means you do not have the correct amount or "charge" of refrigerant in the system.

Low charge can cause freezing of your coil indoors (A-coil/evaporator) which is bad for the system. It also means more stress on the compressor from less cool refrigerant returning to cool it down.

A technician has gauges to measure pressures and knowledge on how to measure superheat and subcooling of the refrigerant to determine the correct amount of refrigerant is in. As mentioned a homeowner can't do that kind of work, you need to have EPA certification.

Since the only way refrigerant can leave the system is via a leak, it is in your and the environment's best interest to have it found and repaired.

Good luck.