I replaced it yesterday because it was leaking even though it was less than a year
old.
Not as hard as I thought, but I like Mark Drillock's tip about using a coat hanger
wire with the end bent up to form a hook, to keep the seal from falling into the tank
if it accidentally gets pushed inside. I used a fly swatter with the handle bent.
Filled the tank this morning, slowly while keeping an eye on the seal. No leaks. So
far.
Here's the mystery. When I removed the old seal, it was torn about one third the way
around, between the inner and outer flanges, where it would fit against the tank
flange. That's where it was leaking from. I lubed everything when I installed it
before as part of the full tank seal/crossover tube project, so nothing was forced
into place.
So how did it tear and start leaking after 11 months??

Jerry