After a couple of years owning a Frantz bypass filter, I've come to the conclusion that I want to change the large o-ring more often than I have been to avoid leakage. I've been changing them every 5 or 6 filter changes but sometimes get leakage if they're near the end of their life. I've bought them from We Filter It, the maker of Frantz, but I'm wondering if anyone has a better and cheaper source, or knows the specs for them so I could search the gasket houses online. Other than this occasional slight leakage, I couldn't be happier with the Frantz. TIA, Jim