How many letters does the top answer for “conduit that carries a rapid flow of water controlled by a sluicegate” have?

The most common answer is penstock (8 letters).

Crossword clue: conduit that carries a rapid flow of water controlled by a sluicegate

3 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

penstock 8 letters wn-def

conduit that carries a rapid flow of water controlled by a sluicegate

sluice 6 letters wn-def

conduit that carries a rapid flow of water controlled by a sluicegate

sluiceway 9 letters wn-def

conduit that carries a rapid flow of water controlled by a sluicegate