Squirrel+Insulation+Flex Liner

Checked a 2-year old water heater today. Has been working fine up to the last two weeks. Kept going out. Common vented with a fan-assist furnace. It backdrafted without the furn on and really backdrafted with the furn on. The confusion was paramount at first as I watched one match after another go out as soon as it passed through the burner access opening. 5 dud matches in a row is some coincidence. Finally dawned on me furnace was pushing more combustion products toward the water heater vent than the diverter could handle and what didn't exit the diverter went down to the WH burner compartment and extinguished the pilot. Didn't blow it out, just displaced the air and the starved pilot lifted away and out.

Chimney was lined with aluminum flex. No obstructions at connection. Went on the roof and pulled the cap and flashing. Liner and surrounding clay liner packed with bits of fiberglass insulation. (The clay stops about 2 ft below the top). A light came on in the customer's head. Turns out he's seen a squirrel stealing insulation from the attic next door but didn't know what he was doing with it. Now we know. Several bricks were missing in the top foot or so of chimney. Looks like the little guy entered there, packed the space between the clay and the flex (good). Not satisfied he chewed a nice round hole in the flex and packed it as well (not good). Cust was lining up a chimney service as I was shutting off the equipment.

I'm still baffled as to how all that insulation is packed so neatly up near the top and not a single piece down at the bottom. Also baffled as to why the sucker would be posessed to gnaw through the flex. Industrious varmints to be sure. Part of the mystery solved, the rest I'll never know I guess. Sorry the post was so long but I felt the need to share.

Have a good weekend all

Larry