Any heating system exposed to floodwater must be cleaned before reuse, said Tom Greiner, Iowa State University Extension agricultural engineer.
Even if the heating system works after its “bath,” dirt-clogged chimneys and smoke boxes could cause the furnace to explode. Check the inside of a flooded furnace before starting any fires. Flush sediment from the chimney with a hose or a swab tied on a long stick. Most flues can be reached through a clean-out door above the fire door.
If the heater is jacketed, clean out all mud between the stove and the outside casing. The casing may be removed to give working space. Take the smoke pipe out of the chimney, and reach through the thimble to remove any mud from the lower portion of the chimney flue. This assures a draft for the fire.
In oil burning systems, inspect the fuel storage tank for opened seams. Dismantle the burner and clean all parts with kerosene. Inspect and clean the air blower. Replace fuel filters and clean and dry out the fuel pump. Remove housings that enclose gears, and clean the gears thoroughly with kerosene. Grit in the gears will cause undue wear.
Be extra careful that the fan motor, electric ignition system, and wiring are completely clean and dry before you turn on the electricity. Electric motor cleaning should be left to electricians and repair people.
Check any chimney that has been in contact with water for leaks that may have developed from dissolved mortar. Most chimneys have a foundation in the ground. Check the foundation, and make sure it has not been undermined.
“A good way to check for small leaks in the chimney or furnace is to buy an inexpensive smoke candle from your local heating contractor,” Greiner said. “Follow the instructions furnished. After lighting the candle, trap the smoke in the chimney by restricting the top of the chimney. Leave a small opening so the smoke will rise. Smoke escaping through the masonry will indicate leaks you may not see otherwise. The best repair is a new flue liner.”
Natural and bottled gas heating systems should be checked by a serviceperson to make sure that no water leaked into the controls or pressure regulator. You can remove the burner elements and clean them, but leave the electric controls and regulators to a serviceperson. Replace severely soaked electric blower motors.
When the system is in good shape, have it “okayed” by a serviceperson, Greiner said. Then restart the furnace to see if it works, keeping the heat low. If weather permits, turn the furnace off. High heat may dry the house out too fast and cause excessive warping in the floors and other parts of the building.
Source: Iowa State University Extension Service