The second category of water pollutants includes inorganic chemicals. These are usually substances of mineral origin. Salt, metals, and minerals are examples of inorganic chemicals. The chemicals discussed alphabetically below are the most common inorganic pollutants in Pennsylvania water supplies, or they are of the greatest health concern. Unless otherwise stated, these inorganic chemicals are usually reported in mg/L or ppm units.

Alkalinity is a commonly measured water characteristic that has little meaning or importance to the typical homeowner. It is a measure of the ability of water to neutralize acids. Calcium is a major component of alkalinity, as it is with hardness. Thus, if your water has a high alkalinity, it is probably hard also. There is no drinking water standard for alkalinity.

Arsenic occurs in groundwater from both natural sources and human activities. In drinking water, it is odorless and tasteless. It is relatively rare in Pennsylvania water supplies, compared to those of the western United States.

In Pennsylvania, arsenic can originate naturally from certain types of rock, or it may be traced to deep-water brines produced from gas and oil well drilling or from industrial activity. Arsenic has a primary drinking water standard because it can cause skin lesions, circulatory problems, and nervous system disorders. Prolonged exposure also can cause various forms of cancer. The present arsenic drinking water standard (0.05 m g/L) is being studied and will likely be lowered to 0.005 m g/L in the near future. A recent survey by the U.S. Geological Survey (USGS) found that arsenic exceeded 5m g/L in 5% of wells in Pennsylvania.

Like arsenic, barium occurs naturally in small concentrations in many groundwater supplies. Barium contamination is not common in private water systems in Pennsylvania, but it may occur sporadically in western and northern Pennsylvania near active and abandoned gas and oil wells.

Barium has a primary drinking water standard of 2.0 mg/L because it causes nervous and circulatory system problems, especially high blood pressure. Standard water softeners are effective in removing barium.

Chloride is common in Pennsylvania water supplies, but it rarely reaches levels of concern. It occurs naturally in most groundwater but may become elevated due to leaching from salt storage areas around highways or from brines produced during gas well drilling. Other possible sources of chloride are sewage effluent, animal manure, and industrial waste.

Chloride has a secondary drinking water standard of 250 mg/L because it may cause a salty taste in the water. Groundwater in Pennsylvania usually contains less than 25 mg/L of chloride.

Copper usually originates from corrosion of copper plumbing in the home (see "Corrosivity," below). Copper has a secondary drinking water standard of 1.0 mg/L because it causes a bitter, metallic taste in water and a blue-green stain in sinks and bathtubs. Copper levels above 1.3 mg/L are a health concern because they may cause severe stomach cramps and intestinal illnesses. Copper can be reduced in water using the corrosion control strategies outlined below.

Corrosive water is a term used to describe aggressive water that can dissolve materials with which it comes in contact. It is a problem because many homes have copper or galvanized pipes, lead solder joints, and brass plumbing fixtures. Thus, corrosive water may cause increases in copper and lead concentrations in drinking water. In rare cases, corrosive water may dissolve even PVC plastic plumbing, causing vinyl chloride contamination of the water. This generally occurs only when inferior plastic pipe that was not approved for drinking water has been used. Approved plastic pipe is directly stamped with "NSF" (National Sanitation Foundation) and "Drinking Water" on the side.

Symptoms of corrosive water problems include metallic taste, bluish-green stains in sinks and bathtubs, and, in severe cases, small leaks in the plumbing system. Because corrosive water is not a health concern by itself, there is only a secondary or recommended standard that water be noncorrosive.

Water that is soft and acidic (pH<7.0) tends to be more corrosive, but the only true measure of water corrosivity is a stability or saturation index. These indices use chemical characteristics of the water such as hardness and pH to estimate its corrosiveness. A stability index greater than about 6.5 indicates water that is probably corrosive, with higher values being increasingly corrosive. A negative saturation index value likewise indicates a corrosive water supply. The most common saturation index in use is the Langelier Saturation Index (LSI).

Past surveys of private water supplies in Pennsylvania have indicated that corrosive water is a common water quality problem, present in over 60% of the groundwater wells and springs tested. It tends to be most common in northern and western Pennsylvania where more acidic groundwater is prevalent, although areas underlain by Triassic shales in southeastern Pennsylvania also produce corrosive water. It is least common in the agricultural valleys underlain by limestone where groundwater typically has a higher pH and hardness. Cistern water can be quite corrosive.

If your water test indicates that your water is corrosive, you should test your water for copper and lead. Corrosive water problems can be corrected using an acid neutralizing filter or by replacing metal plumbing with NSF-approved plastic components.

Hardness is a general term used to refer to the CaCO₃ (calcium carbonate) content of water. Hardness does not pose a health threat, but it does cause aesthetic problems. I can ruin hot water heater elements, reduce soap lathering, and make laundry difficult to clean. Moderate levels of hardness are beneficial because they inhibit plumbing system corrosion. Removal of hardness using a water softener is necessary only if the water is causing aesthetic problems. Use of water softeners may result in undesirable levels of sodium in drinking water and may increase plumbing system corrosion.

Hardness may be reported in milligrams per liter (mg/L) or in a special unit called grains per gallon (gpg). One grain per gallon is equal to about 17 mg/L or parts per million (ppm). Since the level of hardness or calcium carbonate means little to consumers, a chart of water hardness classifications has been developed and appears below. A water hardness of about 90 to 100 mg/L provides excellent corrosion control and is usually acceptable aesthetically, but there are no drinking water standards for hardness.

Hydrogen sulfide (H₂S) is a noxious gas that imparts a disagreeable rotten egg odor when dissolved in water. It is a naturally occurring gas that is common in groundwater in parts of Pennsylvania. Very small concentrations of hydrogen sulfide in water are offensive to most individuals. Although hydrogen sulfide is a highly toxic gas, only under the most unusual conditions would it reach levels toxic to humans as a result of its occurrence in drinking water. More often, it is simply an aesthetic odor problem that can be removed using several treatment processes.

Iron is a common natural problem in groundwater in Pennsylvania that may be worsened by mining activities. It occurs throughout Pennsylvania but is most problematic in the western region of the state. Iron does not occur in drinking water in concentrations of health concern to humans. The secondary drinking water standard for iron is 0.3 mg/L because it causes a metallic taste and orange-brown stains that make water unsuitable for drinking and clothes washing.

If lead is detected in your drinking water, it probably originated from corrosion of your plumbing system. Lead was a common component of solders used in plumbing systems until it was banned in 1991. In homes built in the early 1900s, lead pipe also may be present. Thus, if your home was built before 1991 and has a metal plumbing system, it is likely that some lead is present. If your water supply is corrosive (see discussion above), then any lead present in the plumbing system may be dissolved into your drinking water. Lead concentrations are usually highest in the first water out of the tap (known as "first-draw" water), since this water has been in contact with the plumbing for a longer time. Lead concentrations typically decrease as water is flushed through the plumbing system.

A survey in 1989 found that about 20% of the private water supplies in Pennsylvania contained lead concentrations above the MCL of 0.015 mg/L (15m g/L). Lead poses a serious health threat to the safety of drinking water. It is colorless, odorless, and tasteless. Long-term exposure to lead concentrations in excess of the drinking water standard has been linked to many health effects in adults including cancer, stroke, and high blood pressure. At even greater risk are the fetus and infants up to four years of age, whose rapidly growing bodies absorb lead more quickly and efficiently. Lead can cause premature birth, reduced birth weight, seizures, behavioral disorders, brain damage, and lowered IQ in children. The U.S. Environmental Protection Agency considers lead to be the most serious environmental health hazard for children in the United States.

It should be noted that in rare cases, the source of lead in drinking water might be from groundwater pollution rather than corrosion of the plumbing system. Such pollution may be the result of industrial or landfill contamination of an aquifer. The source of the lead usually can be determined by comparing water test results from a first-draw sample versus a sample collected after the water runs for several minutes. If the lead concentration is high in both samples, then the source of the lead is likely from groundwater contamination.

Like iron, manganese is a naturally occurring metal that can be worsened by mining activities. Manganese at concentrations normally found in drinking water does not constitute a health hazard; however, even small amounts of manganese may impart objectionable tastes or blackish stains to water. For this reason, manganese has a recommended drinking water standard of 0.02 mg/L.

Nitrate in drinking water usually originates from fertilizers or from animal or human wastes. Nitrate concentrations in water tend to be highest in areas of intensive agriculture or where there is a high density of septic systems. In Pennsylvania, nitrate concentrations tend to be highest in the southeastern and south-central counties where agriculture is most prevalent.

Nitrate has a secondary drinking water standard that was established to protect the most sensitive individuals in the population (infants under 6 months of age and a small component of the adult population with abnormal stomach enzymes). These segments of the population are prone to methomoglobinemia (blue baby disease) when consuming water with high nitrates. The need for a nitrate MCL has been questioned lately because blue baby disease occurs very rarely in the United States.

Nitrate may be reported on your water test report as either nitrate (NO₃) or nitrate-nitrogen (NO₃-N). Look carefully at your report to determine which form of nitrate is being reported. The primary drinking water standard or MCL is 10 mg/L as nitrate-nitrogen (NO₃-N) but it is 45 mg/L as nitrate ((NO₃).

The pH of water is a measure of how acidic or basic the water is. It is measured on the pH scale (from 0 to 14) in pH units. It the pH of water is less than 7.0, it is acidic and if it is greater than 7.0, it is considered basic. Water with a pH of exactly 7.0 is considered neutral. If pH values deviate very far from neutral, other water quality problems may be indicated. These would include the presence of toxic metals such as lead (at low pH) and high salt contents (at high pH).

It is recommended that the pH of your water be between 6.5 and 8.5 to minimize other potential water quality problems. Acidic water with a pH less than 6.5 is much more common in Pennsylvania than high-pH water, especially in the northern and western regions of the state. In general, pH is an indicator of other potential water quality problems and is very rarely a problem by itself.

Sulfates normally are present at some level in all private water systems. Sulfates occur naturally as a result of leaching from sulfur deposits in the earth. Private water systems with excessive sulfate in Pennsylvania are generally confined to the western portion of the state or other coal mining regions. Even in these areas, surveys indicate less than 10% of the water supplies have excessive sulfate. Other less common sources are industrial waste and sewage effluent.

Sulfate has a secondary drinking water standard of 250 mg/L because it may impart a bitter taste to the water at this level. A proposal also exists to make sulfate a primary contaminant with an MCL of 500 mg/L, because it may have a laxative effect and cause other gastrointestinal upset above this concentration.

The total amount of substances dissolved in water is referred to as the total dissolved solids (TDS) content of water. Waters high in TDS often contain objectionable levels of dissolved salts such as sodium chloride. Thus, high TDS may indicate the presence of other water quality problems. The recommended drinking water standard of 500 mg/L for TDS exists because high quality waters generally have lower TDS levels.

Drinking water should be sparkling clear for health and aesthetic reasons. Turbidity refers to fine particles of clay, silt, sand, organic matter, or other material that might reduce the clarity of water. Turbidity makes water unappealing to drink because of its muddy appearance. Particles also might act to shield disease-causing bacteria from chlorine or ultraviolet light treatment and provide nutrients for bacteria and viruses to flourish.

Turbidity usually indicates direct pollution from surface runoff often during or shortly after heavy rainfall. Turbidity might increase in wells because of borehole cave-ins; it also might increase when water levels in the well are low such as during a drought, because the submersible pump may disturb sediments near the bottom of the well.

Turbidity is usually measured in a special unit known as an NTU or Nephelometric Turbidity Unit. Drinking water should not exceed 1 NTU, for both health and aesthetic reasons. Water with more than 1 NTU of turbidity makes disinfection to kill bacteria difficult and is the primary reason for the 1 NTU standard.