May 5th, 2012 10:19 PM by Dan Howard
What is an “orphan hot water tank”?
That term refers to a hot water tank that previously vented into a chimney with a furnace. If a direct vent (vent to the exterior side wall) furnace is installed, that furnace is not longer keeping the chimney warm enough to draw fumes up the chimney in cold weather. That is an orphan hot water tank.
Why didn’t my heating person change the hot water tank vent when they installed a new furnace?
We don’t know without checking the conditions. The chimney may have been small enough to meet the requirements for proper venting. This is not very common, but possible. Another answer may simply be economics and convenience as well as the bidding process. The typical flue liner costs over $ 100.00, takes about an hour to install, and involves going to the very top of the existing larger chimney and installing the top of the liner and threading the flexible tube down the old chimney. Other methods such as installing direct vent systems may be more convenient, but have higher equipment costs. If a furnace installer includes the cost of changes, their bid will be higher, risking “losing the job.” For some that risk is more of a motivation than safety of clients.