Coliform bacteria are mostly harmless, but they serve as an indicator of water quality. When water treatment systems are working properly, these bacteria are killed. The presence of these bacteria therefore signals that there is a problem with the treatment system. When such a problem exists, water contamination can occur which can cause disease. For this reason, testing for coliform bacteria is important to ensure the safety of drinking water.
Iron in water has a rusty color and metallic taste. It can leave sediment and can cause reddish or orange staining.
pH refers to the acidity or basicity of water. High pH refers to acidic water which has a "soda taste" and slippery feel. Acidic water leaves deposits which can lead to clogged pipes and broken appliances. Basic water has a bitter metallic taste and causes corrosion.
The term hard water refers to high concentration of dissolved minerals such as calcium and magnesium. Hard water does not pose a health risk, but the minerals can deposit on fixtures and can lead to clogged pipes and inefficient and broken appliances.
Nitrates can enter drinking water from fertilizer, sewage, and manure. Once inside the body, nitrates are converted to nitrites. At high levels, this process can interfere with the oxygen capacity of the blood which can lead to deteriorating health and even death. Lower levels lead to long term conditions including: diuresis, starchy deposits, and spleen hemorrhaging.
Radon gas can accumulate in underground water sources. Although Radon is more dangerous in the air, Radon in water also causes an increased risk of cancer development.
Man-made chemicals can enter the water supply. These chemicals have been linked to an increased risk in cancer in the bladder, stomach, colon, and rectum.