Seal it from the inside out. Otherwise, the pressure will just pop the
silicone plug. There is no guarantee it will work, but likely it will
hold. You just have to find the spot or seal the whole stretch of
silicone over again. Run it over the old stuff making sure it has
complete contact with the glass on both sides of the seam.

Do it now. You really don't want to hear waterfalls in your house do
you? I've BTDTGTTS. ;-)

Lilly