Because you're focusing on fasting, which removes toxins from your body, the last thing you want to do is add more toxins with the water you drink. Tap water is easy to get and low in cost. But is it healthy to drink? Unless you know your tap water is safe, drink it only when you're desperate, and look for a cleaner source.
The Environmental Working Group (EWG) obtained almost 20 million records from state water officials. Its conclusion was that the U.S. federal government should perform a national assessment of drinking water. Incredibly, more than half of the chemical pollutants the group found (315 total) aren't subject to any health or safety regulations, so they can show up in your water in any amount, and it's legal.
The contaminants you have to be concerned about in tap water are as follows:
Bacteria
Environmental chemicals
Heavy metals
Parasites
Radiological pollution
Also, public water systems, where the water is filtered, add chlorine and fluoride back into the water. You also have to think about your home's pipes. The type of pipes you have and any corrosion can cause contamination.
To make a decision about whether your water is safe, you may have to do some investigation. If you have a public water system, you have the right to ask for the results from past water tests. The Environmental Protection Agency (EPA) requires utilities to provide a consumer confidence report. If you have well water, you'll have to have it tested yourself.
Having your water tested by a laboratory takes away all the guesswork. Your local health authority may offer free test kits. For a great resource on certified testing labs and water in your area, call the EPA's drinking water hot line (800-426-4791). The EWG also has an information site where you can see how your state's water ranks.