To replace an old vent cap, first pull apart the duct at the last joint inside the house. If they don't pull apart easily, look for small screws holding the sections of pipe together. Next, remove the screws or nails used to attach the cap to the siding and cut through the caulk around the edges (Photo 1). Pull out the cap, scrape away old caulk and dirt, and then wipe the siding clean so new caulk will stick.
Cut the new vent pipe to the same length as the old one, then slide it through the wall. Screw the cap to the siding and caulk around the edges with paintable caulk.
Finally, join the old duct inside the house to the new vent (Photo 2). Vent caps are available for $8 at home centers.
Source Citation:Smith, Eric. "Replace a broken dryer vent cap.(home care & repair)(Brief article)." The Family Handyman 58.7 (July-August 2008): 12(1). InfoTrac Small Business eCollection. Gale. BROWARD COUNTY LIBRARY. 9 June 2009
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