Immediately upon moving to my new QTH, I was also struck with an S9+ noise
problem. Although it was not present all the time, I was certain that it was
caused by the electric company's high voltage lines just above my back yard
fence. After much investigation, they were convinced that their system was
clean and was generating no noise. They were right. One night, late at
night when everything in the house was still and quiet, the S9+ noise came
back, right in the middle of a QSO. I tore off my headphones in disgust,
just in time to hear the familiar clunk sound that was made by the ice maker
when its motor was running, dumping the ice cubes out of the trays into the
bin below. When it finished, I put my headphones back on. Yep, no noise. 40
meters was as quiet as the rest of my house. I replaced the ice maker and
never had the problem again.

After you try the helpful recommendations by KB7QHC, try to isolate the
noise by turning off one at a time every piece of equipment that you have in
your house, being careful to test for the presence/absence of noise after
each one. Remember that some items are still powered after you turn off
their power switches. You will have to unplug these. Be sure to unplug your
house's heater. Check that lightbulbs are completely screwed into their
sockets so that there is no electrical arcing when it is turned on. Turn off
and unplug your computer, video displays also.

If I were you, I would temporarily remove the ATU from the antenna feedline
completely and unplug it so that it cannot draw any power. If it is an
automatic unit, it will have motors in it. If your ATU is not itself the
cause of the noise, changing its location will have no effect on the noise
at all.

Another thing that comes to mind is the ARRL publication on RFI. We usually
think of RFI as something that we hams cause to someone else, but it can
often be the case that we are the ones affected by noise caused by others or
other electrical items in the house. That book has been very helpful to me.

Oh, yes. About the family riot. You can prevent this by enlisting the help
of the kids in hunting down the problem. This puts them on your side. I'll
bet they will be thrilled in being asked to help you solve a problem.
Children don't often get a chance to help parents solve a problem.

One last thing. Don't give up. You can solve this.

VY 73 DE N6UF