倒 has two readings and they sit at opposite ends of the meaning space. dǎo (3rd tone) = something goes DOWN: a person falls (
摔倒), a building collapses (
倒塌), a business fails (
倒闭), a regime is overthrown (
打倒). dào (4th tone) = something gets FLIPPED or REVERSED: pour out a liquid (
倒水), turn an image upside down (
倒影), back up a car (
倒车 — note the SAME chars also read dǎochē meaning 'transfer between buses'), or as an adverb meaning 'on the contrary' (
倒是). Quick test: if a thing toppled or collapsed → dǎo; if a thing was inverted, poured, or it's 'but/yet/actually' → dào.