Abstract: A system for injecting a laundry chemical into a washing machine includes means for injecting a chemical into a washing machine and coin-operated means for actuating it. One embodiment includes interconnected first, second, and third components configured for use with a source of a laundry chemical, a source of water, and a washing machine of the type having a washing machine cycle, a start switch for starting the washing machine cycle, and a known water flow pattern that occurs after the washing machine cycle has started. The first component produces a first signal indicative of the washing machine cycle having started, the second component produces a second signal indicative of a flow of water from the separate water source into the washing machine, and the third component responds to the first and second signals to identify an occurrence of the known water flow pattern after the washing machine cycle has started and control the injection of a chemical into the washing machine accordingly.