Clearing the sewer line to the real estate editor:

July 18, 1980

Every six months we use a compound made by the Hercules Chemical Company inc. to keep the sewer line clear of roots.IT is called R-D (root destroyer). The company is at 84 Fifth Avenue, New York, NY 10011.

Active ingredients are copper sulfate and pentahydrate.

It has been completely effective for several years in keeping our sewer line clear. Frances P. Matthews Sun City, Ariz.