The EPA requires all water suppliers to give a yearly report to their customers. This report is also called a consumer confidence report. It includes information on the source of the water supplied and any contaminants found. You can contact your local water supplier for a copy of the report. You may also find it online. There are more than 155,000 public water systems in the U.S.

Bromate and chlorite are known as disinfection byproducts. They form when disinfectants added to drinking water combine with organic material in the water. Giardia is a parasite that gets into drinking water from sewage and animal waste. Nitrates are nitrogen-containing substances most often found in fertilizers. The EPA tracks more than 90 chemicals that may be found in drinking water. No water is naturally pure. This is true even for water pumped from underground. As water seeps through the ground to the aquifer, it dissolves and absorbs substances it comes in contact with. Some of these substances, such as minerals, are harmless. Others can be harmful.

Turbidity is one way to tell how safe water is. Water is turbid if it has tiny particles in it. The higher the turbidity, the more particles it has. It also means the water is more likely to have disease-causing germs in it. High turbidity may make it hard to treat the water and monitor it.

Large cities have water systems that draw from surface water, such as lakes, rivers, and streams. Smaller water systems use groundwater as their source. About 1 to 2 in 10 people nationally use private wells for drinking water.

Most water suppliers add chlorine or another disinfectant to kill bacteria and other germs. Other ways to treat the water depend on where the water comes from. Water that is taken from a river or lake often has dirt, leaves, and other plant material in it. It also has certain contaminants. A water supplier often adds chemicals called coagulants to the water. This makes the dirt and contaminants form clumps and settle out of the water. The water then most often goes through a filter to remove any remaining solid particles. Chlorine is added to kill germs. Water suppliers that draw water from the ground may not need to use coagulants and filters if the water is pure enough.

Young children are more vulnerable than adults to the effects of lead and nitrate. If you have lead pipes in your home, the EPA advises that you use the cold water tap for making baby formula, drinking, and cooking. Let the water run for 1 minute or more if you haven't used the tap in at least 6 hours. If your water supply contains nitrates and your child is younger than 6 months of age, talk with your health care provider about finding another water source.

Both bottled water and tap water are safe to drink if they meet the standards set by the EPA and the FDA. Some bottled water gets more treatment than tap water. Other bottled water gets less treatment or is not treated at all. Bottled water that contains sparkling water, seltzer water, tonic water, or club soda is considered a soft drink. It is not regulated under FDA regulations for bottled water. Mineral water comes from an underground source and contains at least 250 parts per million of dissolved minerals. Spring water comes from underground water that flows to the earth's surface. It can only be collected at the spring. Artesian water comes from underground water that is under pressure. That pressure pushes the water to the surface after a well is drilled.

Most people do not need to install a home water treatment system, according to the EPA. But if your water is unpleasant to drink, treating it can make it taste better. If you have young children at home or someone with a weakened immune system, treating the water yourself can help make sure that harmful chemicals or germs have been removed. Read up on the available products before you buy one. Decide what the purpose of the home treatment will be: Do you need better-tasting water? Are family members coming down with frequent bouts of diarrhea? Know what risky places are near you and your water supply. These include landfills, gas stations, areas of fracking (hydraulic fracturing) drilling, and dry cleaners. No single treatment system can remove all contaminants. Also consider a home water system if you have a private well.