We moved into this house six months ago and love the water softener (though we don't understand how to do more than refill it!) and besides the noisy regeneration late at night we've never had a problem until now. Four days ago it started this awful high-pitched noise that is constant, though fluctuates in intensity throughout the day. It stops while water within the home is being used but returns immediately when water is turned off. The noise is coming from the top of the water softener tank. We tried flushing it out (thinking air bubbles?) by turning on every water faucet in the whole house until some wouldn't even drip, but once they were off the sound resumed. Can you help me fix this? We are do-it-yourselfers and would rather not call a tech unless needed. And this noise is headache-inducing!

I high pitched noise (loud squeal) is generally an indication the valve is constantly back washing. Look to see if water is running to the drain constantly. If this is the case then there is a problem with the valve and it will need to be repaired asap. If this is the case the softener should be by-passed until serviced. The reason the noise lessens during water usage is because pressure is being relieved from the tank. What model of softener is this? If you can take the cover off and post another pic this will help.
RJ

Close and Open by-pass valve... See if that helps

It didn't help, but it verified that the bypass valve was the cause of the sound! Thanks : )

RJ,
Thanks for the help- I can't figure out how to upload any further pictures or edit the original post. When we turned the bypass valve for intake water the sound stopped. It is currently bypassed and (yay!) quiet. Is it possible that it is the bypass valve itself that is squealing or is there some other valve nearby it could be? I would say it sounds like it is coming from the bypass valves area. Generic advice needed; is this a regular ol' plumbing job (once properly diagnosed) or are we in need of a professional? We don't want to break anything but have done sink, toilet and shower repairs before (all fairly simple and straightforward)
Information from the sticker:
Model #: AQC 75 CV 50/60 HZ
Serial#: 395474
Manufacture date: 01/06/2002

Thanks for any other information you might have for us!

You will need a professional. It is running to backwash. The high pitch squeal is caused from the high flow of water being forced through the drain line flow control. There can be several causes for this and it needs the proper diagnostic to repair.
RJ

After searching on-line I see it is a Rainsoft system. You will need to contact them for service. The reason the sqeal stopped is because the water is shutoff to softener when by-passed.
RJ

Thanks so much- I found a local authorized repair shop for Rain Soft. WIll proceed from here using their help. Thanks!

Great... Let us know how you did ! Milo

Where I can get rainsoft spare part(electrical & mechanical)