I made a serious mistake in using automotive antifreeze in the Konnarock
septic system and may have severly damaged it.

I strongly advise NEVER TO USE automotive antifreeze in the Nantucket 
sink, shower or bathtub drainage traps.

==> Instead I would purchase one or two gallons of RV-Antifreeze at Home Depot
and take them to the Island to use in the traps on Nantucket

The hot water tank, the pressure tank and the hot and cold water supply pipes
should be drained as before.