Bad smells and tastes are an indicator of bad water. But not always.
Some people trust their palate when it comes to what kind of water is safe to drink. The tastes and smells of bleach, iron, and other obvious toxins convince them that they can intuitively gauge the drinkability of their tap water. The problem with this approach is that many toxins and pollutants do not necessarily have a taste or smell.
Arsenic does not have a taste or flavor, but its side effects can be fatal. Arsenic in drinking water, which often comes from agricultural runoff, can cause an increased risk of skin, lung, bladder, and kidney cancer. It can also cause skin conditions such as hyperkeratosis, which is a thickening of the outer layer of the skin that causes calluses and corns on the hands and feet. See: https://www.health.harvard.edu/a_to_z/hyperkeratosis-a-to-z for more information.
Nitrate in water is one of the most common water pollutants, and can come from runoff from ground irrigation and animal and human waste. People cannot see, smell, or taste the presence of nitrate in the water, but its effects can be harmful, and even fatal, for people. This is especially true for babies.
Bacteria and Viruses
Waterborne pathogens are often transmitted from ground runoff, irrigation, and animal and human waste runoff. The many diseases that can be transmitted via water are many times undetectable with taste, smell, or sight.
Perhaps the most commonly feared toxins, lead is without a smell. It can even sometimes taste sweet, leading people to not identify its presence in their water. The effects of lead in drinking water are significant and are not something to dismiss.
The list goes on, as do the risks. The best way to know if your family is protected from undetected toxins in water is to have your water tested. Consult a trusted, certified water expert to test your water and see what kinds of toxins may be hiding in the water from your tap.