Sand Like Grit in burner
Its a furnace vent, all metal tubing - joins with the water heater vent at about 10 feet. Its vented straight up, two floors to the roof. So I say about 25 ft. Downdraft unit. Probably a good amount of cooldown before the exhaust makes it to the roof. Flame on this unit has always looked the same since I can remember. I was wondering if it somehow came with the gas (gas company getting grit into the system?). This unit leads the other one in usage.
Other identical unit in the attic is laid horizontal, vents up about 5 ft - never had that grit, but also hasn't had a new ignitor since it was last serviced.