I recently had a situation and following discussion regarding chimneys and sleeving water heaters after a new furnace was installed. I have several pictures attached showing different problems all relating to homes with a direct vent furnace and no sleeve (or chimney liner) installed to the existing water heater.
Pictures 1-2-3 are from the same home. The lining looks to be in good shape for the 5% that is visible. No rain cap, no sleeve to the water heater, visible water at the bottom of the chimney. Looking at the 3rd photo, there was some evidence of back-drafting in the past shown with the melted pipe insulation.
Picture 4 shows a badly deteriorated flue liner (a chunk has fallen and is wedged in the chimney) with a direct vent furnace and an originally installed water heater. This home was built in the 1970’s.
Picture 5 shows the top of the water heater where again evidence of back-drafting has occurred. Scorched top, melted insulators, etc. This water heater also vented to a chimney that was no longer used for the furnace.
If the chimney is no longer being used for any combustion appliance, I mention to my clients to consider removing the chimney at some point in the future to eliminate the maintenance that will be required at some point.
If the chimney is of original construction and designed for a water heater and furnace and the furnace is upgraded to a direct vent, the chimney size probably is no longer correct. This is the upper Midwest and we frequently see very cold temperatures (below freezing for months on end). Would this be a defect and the addition of a sleeve to the water heater be an option to be professionally evaluated and installed?