Is it safe to drink tap water?

People who live in America expect safe drinking supplies straight from the tap, but according to a Natural Resources Defence Council report released in 2017, the reality is very different. There is an almost 25% chance that your mains supply has not been properly checked for impurities, or is not safe to drink as per federal law.

The NRDC, which is an environmental pressure group based in New York, found that during 2015 nearly 77 million Americans were living in areas where safety regulations were not being adhered to. A lack of communication means that many residents cannot make an informed decision about the drinkability of their supply, which may contain quite serious pollutants, like arsenic, lead and nitrates.

A more recent global project which looked at the problem of contamination found that of the 159 specimens drawn from all five continents, over 80% contained plastic microfibers. The work was carried out by students from the State University of New York and the University of Minnesota but managed by investigative journalists at Orb Media. Worryingly, they discovered that in the USA, 94.4% of supplies showed the presence of plastic fibres, a higher than average level. At the size and concentration these particles appear in, it’s certainly possible they could damage human cells and therefore, organs. These are likely to have entered the supply from a number of sources, but the researchers speculate that clothing and carpets are the most likely points of origin.

Rusty water runs out of a faucet

A separate study, carried out by journalism students from News21, found that close to 63 million Americans, spanning a geographical area that stretches from New York City to California, could have drunk unsafe supplies more than once over the decade to 2017. Over the course of their investigation, they found 680 000 issues with the Environmental Protection Agency, these related to the quality of US tap water and how the agency was regulating it.

Local Systems Under Pressure

These studies reveal that local systems are deteriorating after more than half a century of abuse. Damage to distribution pipes, faulty plant equipment, industrial pollution, and agricultural runoff have all played a part in this modern problem. Regions that were aware of an issue, habitually took over two years to make things right. Moreover, some breaches of EPA standards are still unresolved, according to the agency’s own Safe Drinking Water Information System.

Unbelievably, considering the USA is one of the richest countries in the world, the main block to progress is economic. Small rural communities in remote areas of the country simply do not have the funds to purchase up to date piping and tools to ensure their supply is properly filtered. That means noxious substances from a range of sources find their way into the supply of millions of people, including the very young and the very old, who are most at risk from bacterial infections and other forms of contamination.

Filter system for water treatment. Removes lead and further contaminants.

How do Contaminants Enter the Supply?

We assume that if tap water has travelled through treatment works, then it has to be crystal clear and completely safe to drink. To a certain extent, this is true, as filters and disinfectants remove the majority of impurities. However, the process is not completely reliable, and toxins can either sneak in or circumvent the plant on their way to your tap.

Combating the hazards associated with pollution must be done on two fronts. First, we need to stop pollution from reaching rivers and lakes, and second, we need to properly treat it when it arrives at a plant. When problems arise with either, it is often because the law is hazy regarding which natural sources the 1972 Clean Water Act covers.

The lion’s share of aqua systems in the US are sustained by groundwater, this is usually cleaner than that which sits on the surface because it has been filtered naturally through layers of rock and soil. In larger urban areas, it is more often surface systems like lakes and rivers which feed the residents supply, and because more people live in cities, more Americans get their supply from a surface source. This means the operations at a treatment plant are doubly important.

How is Raw Water Treated?
Before supplies from any natural source are piped through to our homes, there are five stages which are designed to clean it up.

The First Filter

When an untreated liquid is first introduced to a plant, it is combined with a sulphate salt called alum, and a cocktail of other chemicals. After a while, a reaction occurs in which fine sticky particles draw in any fragments of dirt that are in the fluid.

As the debris combines into larger lumps it starts to get heavier, eventually, its weight will be enough to make it sink to the bottom of the treatment tank. Here it settles, forming sediment underneath the clearer water that moves on to the next step.

The Second Filtration

Once the bigger scraps of dirt have been taken away, the liquid flows through a more complex sequence of filters that remove tiny flecks, even those as small as bacteria. The filters used often contain charcoal, sand and gravel, recreating the underground filtration process which happens in nature.

In past years, filtration was the final stage before the end product was ready for human consumption. Now an extra stage is included, where disinfectant chemicals are poured into the mix and wipe away any remaining microscopic lifeforms. Most treatment plants will use chlorine at this point, but sometimes other sanitisers could be used as well.


Once the treatment stages are completed, the water is moved into a reservoir or tank until the chemicals have taken effect. At this point, it is considered ready and released to flow into our homes

How Can Anything Go Wrong
Faced with such a robust series of precautions, most unsafe elements are quickly eradicated, especially after the addition of chlorine. Unfortunately, no system is perfect and there have been a number of high profile incidents when the procedures have failed. In 1993, a microscopic parasite known as Cryptosporidium, infected the mains supplied of numerous homes in Milwaukee, Wisconsin. 400 000 people became ill and tragically, over 100 people died as a result of the infection.

We already know that rivers and streams are plagued by pollution, and when treatment centre piping has to pass through these areas, badly maintained equipment can let in microscopic amounts of contagions. Also, reservoirs which are considered safe can be re-polluted by runoff streams, accidental chemical spills, or even malicious dumping. When they are added in the wrong amounts, even disinfectant chemicals which are meant to safeguard our mains supply can present a serious threat.

Reverse Osmosis System on white background. Tap water runs through membrane.

What Can You Do at Home

Bottled may seem like a sensible alternative to tap, but it is a far more expensive option and plastics play a major role in polluting our planet. It’s worth remembering that despite the scares of recent years, most taps provide safe drinkable supplies, and if you’re not sure you can ask your provider for confirmation. Their ‘Right to Know’ policy will keep you up to date on the quality of your local supply, so give them a call if you have any concerns.

If there are problems with your local supplier, or if you would prefer a safer alternative, a good home filtration system can give you peace of mind. These range from small-scale cheaper solutions, like jugs that sit on the kitchen worktop, to whole house filters that are much pricier.

These information were not written by the American Food and Drug Administration, or any other official authority. This site and its products do not promise to diagnose and cure diseases, or protect you from them. Always consult your doctor when you are sick.