The difference between purified, distilled, and tap water, and which is the best choice for drinking

Ashley Laderer

May 8, 2020, 21:06 IST

The difference between purified, distilled, and tap water, and which is the best choice for drinking

Drinking tap water is fine if you live in an area with a good purification system.Thanasis Zovoilis/Getty Images

The quality of your tap water depends on where you live.
Purified water is usually a good option since the purification process removes chemicals and impurities from the water.
You should not drink distilled water since it lacks naturally-occurring minerals, including calcium and magnesium, that are beneficial for health.
This article was medically reviewed by Tania Elliott, MD, who specializes in infectious diseases related to allergies and immunology for internal medicine at NYU Langone Health.
Visit Insider's Health Reference library for more advice.

We're all told to drink more water to stay hydrated and healthy, but what type of water should we be drinking? There are various options. We had experts break down the differences between purified water, distilled water, and tap water, so you can choose which is the best for you to drink.

Tap Water

Tap water is water that comes directly from a valve in your home, whether it's the kitchen sink, bathroom faucet, or the washing machine hose.

Is tap water safe to drink?

The quality of your tap water will depend heavily on where you live. You should be an educated consumer and determine what type of tap water is being delivered to your place of residency to decide if you should be drinking it or not, says Catherine Carpenter, Ph.D., epidemiologist at the UCLA Fielding School of Public Health. Usually, your water bill will provide a breakdown of the particulates and constituents found in your tap water, so be sure to take a look.

The tap water in your home could be equivalent to consuming bottled water, or it could be unhealthy and filled with contaminants. To give you an idea of the range, the Orange County in California has some of the purest tap water in the country, as the county goes above and beyond federal guidelines for what constitutes safe drinking water. On the other hand, Pittsburgh, Pennsylvania and Milwaukee, Wisconsin are cities that are known to have unhealthy tap water with high levels of lead.

Additionally, you can go on the Environmental Working Group's tap water database to search by your zip code, and you can learn if there are any known contaminants that exceed EWG's health guidelines. It also will give you advice on which water filters to purchase in order remove a particular contaminant.

To be even more sure, you can actually submit your tap water for analysis if you're concerned about its safety. The Environmental Protection Agency has a page where you can choose your area and they will provide you with certified laboratories nearby that can test your water quality.

What is in tap water?

Andrew J. Whelton Ph.D., Associate Professor of Environmental and Ecological Engineering at Purdue University says that in general, tap water contains a variety of minerals and organisms. Tap water delivered to buildings is not sterile, and it may vary in quality even within the same city or town. Furthermore, he says that tap water quality levels can fluctuate based on what room you're in, the time of year, and plumbing.

According to Whelton some minerals that may be found in tap water are chloride, sulphate, copper, iron, manganese, and zinc. Levels vary place to place, and different countries have different regulations regarding how much of each is allowed in its water supply.

It is important to remember that not all "contaminants" in tap water are harmful. Potassium, magnesium, and calcium, for example, are all beneficial nutrients that may be in your unfiltered tap water.

Purified Water

If you live somewhere where the tap water is unfit to drink, you'll likely be relying on purified water. This can be obtained by purchasing purified bottled water or by using a filtration system in your home.

What is purified water?

Put simply, purified water is water that's been mechanically filtered or processed to remove chemicals and impurities, according to Carpenter. The purification process removes contaminants including bacteria, chemicals, and toxins from tap water or ground water.

Different water purification treatments are designed to remove different impurities from the water.

How to purify water

The three most common methods of at-home water purification are:

Carbon filters: This is the most inexpensive method, though not the most thorough. If you've used a Brita pitcher, you've experienced the effects of carbon filters. The simplest carbon filters will remove chlorine and improve taste and smell. More advanced ones can remove further toxins like lead and mercury. They work by utilizing activated carbon which will bond to contaminants. Pitcher filters are very common for this type of purification, but you can also get a faucet-mounted filter or under sink filter.
Reverse osmosis systems: This is often considered the most effective way to purify water, since it filters out anything larger than a water molecule, and thereby removes most contaminants. However, it's pricey – reverse osmosis filters that are installed under your sink can cost $200 or more.
Ion exchange filters: This method is best for dealing with hard water, which is water that's high in minerals like calcium or magnesium. Ion exchange filters use a chemical process that reduces levels of calcium and magnesium, and usually replaces them with sodium.

Distilled water

While usually seen as its own category, distilled water is a type of purified water, according to Carpenter. Distillation is a process where water is boiled and steam-condensed, which leaves solid contaminants behind. You are left with essentially pure water. It will lack naturally-occurring minerals.

Water that has undergone distillation will be purer than if it was purified by a carbon, ion exchange, or reverse osmosis filter. Although that isn't always a good thing, depending on the person who's drinking it.

What type of water should I drink?

According to Carpenter, there is no one-size-fits-all answer for choosing the best type of water to drink. The answer will depend on the quality of tap water where you live, if you have any purification systems in place, and if you have any health conditions. Taste also comes into play.

Drinking distilled water is usually not preferred. It may put individuals at greater risk for nutrient deficiencies since it lacks any minerals that may be beneficial to health. Additionally, it can cause problems with your teeth. Whelton says that minerals in your teeth can leach into the mineral starved water – and he doesn't generally recommend it.

When it comes to purified water, there are many variations. A certain amount of minerals in water can be beneficial. "Depending upon the degree of purification and the water source, some purified bottled water that retains minerals can provide a source of daily intake of calcium and magnesium," says Carpenter.

Whelton also says minerals may be added into purified water. "Water that has been demineralized is often remineralized after treatment so that it doesn't have bad taste or pose health risks, [such as] extracting minerals from the person."

According to Carpenter, if you have health conditions such as kidney disease, cardiovascular disease, or have diminished or excess calcification, it's important to make the right choice with drinking water. Talk to your doctor about what's best for you.

Even if you don't have a pre-existing health condition, you may still want to chat with your doctor about what type of water is the best for you, and of course, check on the safety of your location's tap water.