During a driving rain/nor'easter kind. I get some water behind my accentra insert. I have never noticed it going down the 4" liner, but it seems to drip around it, down the original chimney. I had a chimney guy come out to look at it this week, and he recommends re-flashing, and putting a 4" cap on the liner, and sealing off the old pipe around it. The estimated cost is $400. That seems a bit much for a few drops of water behind my insert, or is it worth it in the long run?