mjhjmtu

It's a short story that I read in a book at some point in the 1990's. It was the French translation, so it might have been older. I believe it was a short story by Isaac Asimov, set in the early days of the Galactic Empire from Foundation, but I may be wrong.

The story had someone sent to visit an asteroid colony, might have been a mining colony, for some reason. The visitor is a sort of official and soon realizes that there's something wrong when he interacts with the local officials, and he's told the guy in charge of maintaining the plumbing is on strike.

Short explanation ensues and the visitor learns that no one in the colony would make direct contact with the plumber because he is unclean thus outcast, since he also deals with waste and the dead. Visitor offers to go negotiate on behalf of the colonists because he's not bound by their caste system, to which the colony official happily agree. The negotiations go well and the plumber resumes his work.

However, when the visitor tries to go back to the colony, he finds the way blocked and he is directed, through automated doors and voices coming out of speakers, back to his shuttle and asked to leave the colony because, since he was in contact with the plumber, he's become unclean too thus the colony officials cannot get in contact with him anymore.

Strikebreaker by Isaac Asimov

The world in question is Elsevere, an extrasolar planetoid a hundred
miles in diameter which is home to an insular, idiosyncratic human
colony of thirty thousand people, who have inhabited the planet in all
three dimensions. A rigid caste system has developed, with each
occupation being confined to a particular set of families. A visiting
Earth sociologist, Steven Lamorak, learns that Igor Ragusnik has gone
on strike.

The Ragusnik family operates Elsevere's waste processing facility, and
over the generations, the Ragusniks have become a one-family caste of
untouchables, forbidden all contact with the rest of the colony. Igor
Ragusnik demands that his family's isolation end. Elsevere's ruling
council refuses his demands, and if the strike continues, the
planetoid's waste processing machinery will break down and every
colonist will die from disease. Although the machinery is not
difficult to operate, the taboo is so strong that no other Elseverean
will do so.

Only Lamorak is willing to speak to Ragusnik. As neither side will
give in, he reluctantly volunteers to operate the waste processing
machinery himself; as an outsider, he has no cultural compunctions
against doing so. Realizing that the ruling council can always import
a strikebreaker, Ragusnik capitulates and returns to work.

Lamorak assures Ragusnik that now that other Elseverians and the rest
of the galaxy are aware of how unhappy he is, they will eventually end
his family's isolation; Ragusnik is unimpressed. Lamorak learns that
he must leave immediately, as other Elseverians will no longer have
anything to do with him. Now that he has worked at Ragusnik's job, he
is an untouchable himself.