How can the average tax-paying citizen find out if(and why) their home phone line is being tapped?

Is there a device, or any other means to detect a tapped phone line? Would asking the local phone co. do any good? Or for that matter,ask the local government if/why they're listening in?
I have a friend that I've been talking to often lately on the phone. Both of us using the good old fashioned "land-lines".
Yesterday, I was both surprised and dismayed when she told me that HER phone line is probably being monitered and to be careful what I talk about.
Since I'm not a criminal, I'm not worried if a lawman "listens in". So I'm asking this question in the name of civil rights and right to privacy.
My friend however, says she lives in an area where the lawmen ARE needed and hears her phone "click" a lot when she's using it. I have no reason to think she's a criminal. Her two sons (19 and 22) are no angels, but nothing even close to a felony or similar. Plus neither one even lives at home anymore, so they don't justify a phone being tapped.

That "click" she hears is probably nothing more that a bad connection. Do you really think the law could get away with tapping phone lines (let's say a mobsters phone) if it could be detected by something so obvious as a "click"ing sound. They would never get any information on anyone.

Generally, using modern technology, it is possible to tap a phone in such a way that the average consumer cannot tell.

In the US, wiretapping when either end of the conversation is inside the US requires a warrant. Yes, even if the other end of the conversation is overseas. See 50 USC 180x (FISA) and 18 USC 2511 (Title III of the Omnibus Crime Control Act).

If the activity is part of normal police surveillance, the warrant would need to be obtained from a regular court, and the court could be asked (by petition) if there is a warrant issued. If the activity is part of covert surveillance, then the warrant would be issued by a FISA court, and all FISA records are sealed.

Just tell her to call the phone company - they can check the line and put her mind at ease. (Of course, they will not anyone if a law enforcement agency has a tap in place for obvious reasons.)

300 million people live in the USA, each person probably averages an hour on the phone each day. Do you really think the govt has the resources to listen to each and every one of these conversations? Even a fraction of them?