I came across a version of this story in an old textbook. (I like old textbooks.) The story circulates widely, but it’s new to me. Here is a telling that names a source, though not necessarily an origin:
Dr. William B. Bean, who in the Archives of Internal Medicine often tilted a lancet at the writing operations of his fellow healers, has passed on the story of a New York plumber who had cleaned out some drains with hydrochloric acid and then wrote to a chemical research bureau, inquiring, “Was there any possibility of harm?” As told by Dr. Bean, the story continues:This post is for Fresca, who likes clarity.
“The first answer was, ‘The efficacy of hydrochloric acid is indisputably established but the corrosive residue is incompatible with metallic permanence.’ The plumber was proud to get this and thanked the people for approving of his method. The dismayed research bureau rushed another letter to him saying, ‘We cannot assume responsibility for the production of a toxic and noxious residue with hydrochloric acid. We beg leave to suggest to you the employment of an alternative procedure.’ The plumber was more delighted than ever and wrote to thank them for reiterating their approval. By this time the bureau got worried about what might be happening to New York’s sewers and called in a third man, and older scientist, who wrote simply, ‘Don’t use hydrochloric acid. It eats hell out of pipes.’”
Theodore Bernstein, The Careful Writer (1965).
[William Bennett Bean was described in 1974 as “a true renaissance man: an articulate clinician, a scholar of the classics, a masterful teller of tales, and a prodigious writer of stories.”]