The answer!
So here is a portion of the letter I wrote to my RV dealer:
"This is the newest and potentially the worst problem to date. On our last trip to Dale Hollow, which was also our first warm weather trip, we noticed an extreme black tank sewer odor emitting from a previously emptied and cleaned tank (although it did have a few gallons of water mixed with tank chemicals in it). After two days of living with it, I searched the internet for several hours, reading a lot of posts about what kind of sewer odor problems there are and what kind of solutions there are. I had already done most of them in the two days prior to going online. The one that struck a chord was the possibility of a wasp nest clogging the vent stack. So up I go! Once on the roof, I removed the vent cap and aimed my flashlight down the pipe. To my dismay, there was a piece of luan plywood blocking the vent. It was wedged 15.5” down the pipe. Now, since I was 250 miles from home, I did not have any type of tool to deal with it other than a coat hanger that I cut and straightened. The coat hanger would not budge the luan. So, we jumped into the truck and made the trip to town. At the local Ace Hardware store I purchased a 3/16” spade bit with extension so I could try drilling out the luan. We returned to the camper an hour later and back up to the roof I went. Using a very weak electric screwdriver (no drill available), I was able to drill several holes through the luan. On the fifth hole, the luan snapped sideways and I was then able to use my trusty hanger to yank it up and out of the pipe. What was REALLY interesting was the line of glue/sealant that was holding the luan in the pipe. I noticed that when I looked down the vent stack expecting to see the glimmer of water in the waste tank. Imagine my second surprise when I saw what looked to be some kind of gauze-like material at the bottom of the pipe. (btw, we have never flushed any kind of toilet paper, etc… down the toilet) So I got my trusty garden hose out of my truck, got back up and fed the hose down the pipe. When it reached the bottom, it clunked, not penetrating the material at the bottom. I banged it up and down vigorously, but it wouldn’t break through. So I retracted the hose, added the nozzle, dropped it back down and had my wife charge the hose, making it fairly rigid. After several more hearty thrusts, it broke through, allowing me to see into the tank through my now watering eyes (hot sewer gases will rush out when you give them a route…). So, almost 4 hours after finding the problem, I solved it. My question is why would I find a piece of luan, cut to fit the inside diameter of my vent stack, glued 15.5” down from the top? And what was the very hard material at the bottom of the stack? I’d like to hear what the quality control experts at Crossroads have to say."
