Learn about the different types of contaminants that might put your family at risk.

negative charge
The electrical charge on an electrode or ion in solution due to the presence of an excess of electrons.
negative head
A condition of negative pressure or partial vacuum.
negative pressure
A pressure below that of the surrounding atmospheric pressure at a specific point; a partial vacuum.
nephelometric turbidity unit (NTU)
An arbitrary unit of measuring the turbidity in water by the light scattering effects of fine suspended particles in light beam.
In electrical systems, the term used to indicate neither an excess nor a lack of electrons; a condition of balance between positive and negative charges.  In chemistry, the term used to indicate a balance between acids and bases; the neutral point on the pH scale is 7.0, indicating the presence of equal numbers of free hydrogen (acidic) and hydroxide (basic) ions.
In general, the addition of either an acid or a base to a solution as required to produce a neutral solution. The use of alkaline or basic materials to neutralize the acidity of some waters is common practice in water conditioning.
A common designation for alkaline materials such as calcite (calcium carbonate) or magnesia (magnesium oxide) used in the neutralization of acid waters.
noncarbonated hardness
Water hardness due to the presence of compounds such as calcium and magnesium chlorides, sulfates, or nitrates; the excess of total hardness over total alkalinity.
normal solution
A solution containing a gram equivalent weight of a substance in a liter of solution.