Water tests measure the presence of contaminants. A contaminant is any physical, chemical, biological or radioactive material in the water. Physical contaminants include any substance that affects the physical appearance or properties of water. Such as sediment or organic matter present in lakes, rivers and streams.
Chemical pollutants can be naturally occurring or man-made. For example nitrogen, pesticides, metals and pharmaceutical toxins. Bacteria, viruses, protozoa and parasites are considered biological contaminants. Radioactive contaminants are chemical elements with an imbalanced number of protons and neutrons. Due to this imbalance, the atoms emit radiation. Some of these radioactive contaminants include cesium, plutonium and uranium.

The type of pollutant depends on the type of health effects it may cause. Acute reactions occur hours or days after taking. Microorganisms such as bacteria and viruses are most likely to cause these health effects.
Most people's bodies are as capable of fighting microbial contaminants as they are bacteria. So these acute pollutants usually do not have permanent effects. However, when intake is high enough, they can be dangerous. Especially for people with compromised immune systems.
Long-term consumption of pollutants above safe levels can have chronic effects. These pollutants include chemicals, radium and arsenic. The resulting health risks include cancer, liver problems, kidney problems or reproductive difficulties.

Arsenic
Arsenic occurs naturally in rocks and is sometimes found as an industrial byproduct, and exposure to this harmful pollutant can lead to cancer, skin changes, gastrointestinal symptoms or cardiovascular and nervous system dysfunction.
Fluoride
Everyone reacts to minerals differently. The same goes for fluoride. As with all minerals, overexposure remains a danger.
Germ
There is a greater risk of finding bacteria such as E. coli and Cryptosporidium in your household water supply than in public drinking water systems. These pathogens enter the water through the feces of infected humans or animals. As a result, severe intestinal disease occurs.
Lead
Lead usually enters water systems through pipes. This is a top concern for homeowners. Because it is especially harmful to pregnant women, babies and young children. Harmful effects range from stomach pains to brain damage.
Calcium and magnesium
Minerals like calcium, sodium, and magnesium don't necessarily have a direct impact on your health. But their presence can cause hard water. Hard water can cause dry, itchy skin. Another sign includes the shortened lifespan of clothes and household appliances.
Nitrate
Phosphates and nitrates can leach into groundwater. These chemicals can cause a range of health problems, such as kidney disease and cancer. These risks are especially high for pregnant and breastfeeding women, infants, and the elderly

Common signs can help you know when to get a water test. First, a coliform test is recommended if you have a family member with recurring gastrointestinal illness.
Analysis for pH, lead or copper may indicate whether your home has lead in the plumbing.
If you live near an agricultural area, testing for nitrates, pesticides, and coliforms is recommended.
Hardness and total dissolved solids (TDS) tests remain the best option for households with itchy skin, spotty meals, and scaling on fixtures and appliances.
Staining of pipes and laundry rooms may require detection of contaminants such as iron, copper and manganese.
If you notice that your drinking water is salty, or you live in a place with a lot of salty roads, experts recommend that you choose a method that tests for chlorine, TDS, and sodium.
Finally, living close to a gas station or underground fuel tank may require testing for volatile organic compounds (VOCs).