[rdunk]

Yes, the O'ring does grow. After wrestling with mine, I have found that putting a little Vaseline in the groove on the housing will hold the O'ring just fine. If you try this, you will probably still have my experience, which is, the O'ring will still seem too big. But suprisingly, if you continue to press the O'ring down, it will fit into the groove, and will stay down during the re-installation of the filter.

I don't fill the groove with Vaseline, but try to put just enough in to get the O'ring to stay-put. Always works for me!

Our unit is nearly four years old, and I am still using the original O'ring.