I water tested the window and could not get it to leak. I water tested the roof and gutter system and it still would not leak. The only way I got the bay window to leak was by clogging the downspout on the gutter and applying water. I examined the shingles, they did not appear to be in to bad of shape. Just one place left to look before I blamed the leaking bay window on the gutter being full, the attic. The pictures show that the roof is bad. Rust on nails, discolored brittle sheeting. The water was flowing through the shingles, down the sheeting, into the wall and dripping through the bay window.