No. There is no state law requirement for a public hearing when reducing (or increasing) a city’s water utility rates for customers. There might be a local requirement for a public hearing but there is not a state law requirement. A city may also choose to hold a public hearing for such utility rate changes, even if the proposal is for a decrease and not an increase (e.g., for transparency and public input).
For solid waste utility service rate increases only, there is a 45-day notice requirement in RCW 35A.21.152(1) for city contracted or directly provided solid waste service:
(1) A city that contracts for the collection of solid waste, or provides for the collection of solid waste directly, shall notify the public of each proposed rate increase for a solid waste handling service. The notice may be mailed to each affected ratepayer or published once a week for two consecutive weeks in a newspaper of general circulation in the collection area. The notice shall be available to affected ratepayers at least forty-five days prior to the proposed effective date of the rate increase. [Emphasis added]
Even for solid waste disposal services, there is not a public hearing requirement or any required notice of a rate decrease, just proposed rate increases.
Regarding water utility service rates, RCW 80.28.010 and the recent West Terrace Golf (2024) case require city water rates to be reasonable, considering the value of water service to the public and fair compensation to the city for providing the service. Although these authorities impose no specific public outreach requirements in setting water service rates, holding a public hearing before adjusting water service rates could help to establish the “reasonableness” requirement in these authorities, so holding one may be worth considering in that context.
