When I bought this Trillium
about 7 years ago I removed
and resealed all the windows. They have not leaked until
this year when the large on on the back dripped a bit.
As an interim fix I scraped just bit (1/8") of the butyl
tape across the top and about an inch down the sides,
masked it off and used the white bathtub calk around that
area. This winter I will remove and reseal the window
The windows are nearly 40 years old and still do fine in
very heavy rains when the edges are sealed well.