King County local discharge limits: corrosive substances (pH)

The limit: In King County, the maximum limit for wastewater discharged into the sanitary sewer is pH 12.

• The instantaneous minimum limit is violated when any grab sample (a single, random sample) or continuous recording is less than pH 5.
• The daily minimum limit is violated when a recording of 15 minutes or longer remains below pH 5.5 or when four consecutive grab samples collected at 15-minute intervals or longer in a 24-hour period are all below pH 5.5.

Corrosion: Wastewater that is too acid or too alkaline can seriously corrode the sewerage system.

pH: The letters pH followed by a number are used to express the acid or alkaline condition of a liquid. A pH test shows acidity or alkalinity with numbers from 0 to 14. A pH of 7 indicates a neutral liquid, neither acid nor alkaline. Numbers below 7 ranging down to 0 show increasing acidity, with 0 being the most acidic. Numbers above 7 ranging up to 14 show increasing alkalinity, with 14 being the most alkaline.