Someone has just asked me about the device sold to stop
your water pipes and tanks furring up, which consists of
a coil wound around the pipe that is then excited by
an oscillator.

Personally, I think the whole thing to be bollox.

Does anybody know the physics behind it?

I cannot see how orienting the calcium saly ions
in one particular direction will stop furring up
some distance away especially if there has been
turbulent flow in between.

I advised him to get a water softener fitted instead.