Appearance

• The visual appearance of treated water is acceptable to a majority of target consumers.

Key indicators

• No visible color <15 true color units (TCU).
• Turbidity <5 nephelometric turbidity units (NTU) (generally acceptable).
• Iron (Fe) <0.3 mg/L.
• Copper (Cu) <1 mg/L.

Notes and exceptions

• Visual factors include color, cloudiness, particulates, and visible organisms and vary with untreated source water quality.
• Visual factors affecting consumer preference may occur within the device as well as the water itself and include biofilms, scaling, and soap scum due to hard water, animal larvae, and staining due to high levels of Fe or Cu.
• See additional notes under Device performance: turbidity reduction.

Supporting evidence

• World Health Organization (WHO). Guidelines for drinking-water quality: Incorporating 1st and 2nd addenda, Vol.1, Recommendations, 3rd ed. Geneva: WHO; 2008. Available at: http://www.who.int/water_sanitation_health/dwq/fulltext.pdf.
• National secondary drinking water regulations page. United States Environmental Protection Agency website. Available at: http://water.epa.gov/drink/index.cfm. Accessed April 4, 2011.
• Indian Standard for Drinking Water per Bureau of Indian Standards (BIS) (IS 10500:1991).
• Full list of supporting evidence and additional materials.