Could this be Deathworld 2 (aka The Ethical Engineer) by Harry Harrison?
A novel rather than short story and it's the electricians that he ends up with.
In Deathworld 2, Jason is kidnapped by the self-righteous Mikah, who
is determined to bring him back to the planet Cassylia, ostensibly to
be tried for his various crimes but really (because Cassylia does not
want Jason returned, since his huge winnings in Deathworld have helped
the planet propaganda-wise) for use by Mikah's movement to overthrow
Cassylia's government, which they consider corrupt. He forces a
crash-landing on a planet where the human population has regressed.
The technology is extremely primitive and knowledge is split up among
many small clans, each one jealously monopolizing what it knows. Jason
uses his ingenuity to survive, trading his knowledge for protection
and power in one of these clans. He eventually reaches the clan who
has the knowledge of electricity and signals his location to a
spaceship piloted by his Pyrran girlfriend, Meta.
The water that burns reference is from chapter 12 where Jason is kidnapped by the Mastreguloj:
"Do you know to whom you talk?" the masked figure on the far right asked in a high-pitched, shaking voice. Jason examined the speaker carefully.
"The Mastreguloj? I've heard about you. You are supposed to be the witches and warlocks of this town, with fire that burns in water, smoke that will burn the lungs, water that will burn the flesh, and so forth. My guess is that you are the local equivalents of chemists; and though there aren't supposed to be very many of you, you are nasty enough to keep the other tribes frightened."
"Do you know what this contains?" the man asked, holding up a glass sphere with some yellowish liquid in it.
"I don't know, and I couldn't care less."
"It contains the magic burning water that will sear you and char you in an instant if it touches-"
"Oh, come off it! There's nothing in there but some common acid, probably sulphuric, because the other acids are made from it, and there is also the strong clue of rotten egg reek that fills this room.