Jaanus Jogi sent me this link to a back issue of mother earth news
and
their trompe explaination
(It is great to find tromp info in a reputable magazine.(So many
people do not understand the tromp concept or accept that it might
work!)
http://www.motherearthnews.com/arc/4300/ The trompes they used in the
olden days were huge and deep. Please note thatI do not advocate
trompes that are deeper than necessary but I believe large ones are
fine. Those old trompes were sooo deep!
Brian