[rdunk]

My dealer said that the only way to get an o-ring that size was to buy a Shurflow filter, that comes with an o-ring. I haven't done that, because Shurflow filters are not readily available. I plan to replace the Shurflow filter to get away from the stupid Shurflow o-ring problem.

The Shurflow filter doesn't seem to be any better than most standard "whole house" filters, that can be bought most anywhere that sells general household products.