Haw. Rev. Stat. § 54-21
The board of water supply may provide for the accumulation of a fund for the purpose of financing major replacements, or extensions and additions, the average estimated annual increment to which, for a period of ten years, shall not exceed fifteen per cent of the gross revenue of the board in any fiscal year.
[L 1961, c 155, pt of §1; Supp, §145A-11; HRS §54-21]