What's the Difference Between Filtered and Purified Water?

There are significant differences between water that's gone through a filter versus water that's been purified. One easy way to understand the distinction is to remember that not all filtered water has been purified, but all purified water has been filtered.

We use different words to describe the water we drink depending on how it's processed. But what makes one type of water different from another isn’t always clear to everyone. 

Water goes through a process of filtration or purification before it reaches us. These two treatments may sound similar, but they have distinct differences. Knowing these differences can help you make the best decision about the water you choose to drink.

Not really. There are significant differences between water that's gone through a filter versus water that's been purified. One easy way to understand the distinction is to remember that not all filtered water has been purified, but all purified water has been filtered.

Filtered water, as the name suggests, is water that has passed through filters or physical barriers to remove unwanted contaminants. These filters are usually made from materials like gravel, sand, or charcoal. They have small holes (or pores) of several sizes for filtering various sediments out of the water.

As water passes through them, the filters catch the impurities and larger particles in the water. Filtration eliminates germs, bacteria, parasites, dust, and other chemicals. It also improves the water’s taste, color, and smell.

Activated carbon (AC) filters

AC filters are made from materials like charcoal and are processed — or activated — to become highly porous. They're effective in filtering many unwanted elements out of water, including:

• Benzene
• Gasoline
• Mercury
• Radon
• Residual chlorine
• Some organic compounds
• Some pesticides

Most AC filters have pores that measure around one micron — or one-millionth of a meter — in diameter. These filters remove finer chemical contaminants and certain microbes that can  cause diarrheal diseases.

Activated carbon filters are the most common and available option for filtering your water at home. But it’s worth noting that these types of filters can’t remove some minerals, such as:

• Calcium
• Chloride
• Fluoride
• Magnesium
• Nitrate
• Other metal ions

One benefit of filtration is that it’s cheaper and more straightforward than water purification. Most home water filters are simple, gravity-activated devices that don’t require any electricity. Many water filters are also portable.

Another advantage of filtration is that it keeps many beneficial minerals in the water. Calcium, magnesium, and sodium are some examples of minerals that are important for your health. They help protect you against certain cardiovascular diseases, and evidence suggests that magnesium and calcium in drinking water may protect against various types of cancers.

The process of filtering water can vary in efficiency depending on the filters used. Many home filters can be slow, and they need to be cleaned and replaced regularly to remain effective. Additionally, filters aren't foolproof, and filtration can’t remove 100% of unwanted chemicals and particles from water. This means that filtered water is unlikely to be completely pure and free of all contaminants.

For water to be purified, it must undergo different treatments to eliminate the things that standard filtration can’t. Purified water is also filtered, but has to go through one of several additional purification processes. The particles and contaminants removed from water during purification vary depending on the specific purification process but can include:

• Aluminum
• Arsenic
• Barium
• Chloride 
• Copper
• Lead
• Mercury
• Radium
• Silica
• Silver
• Sulfate
• Uranium

Water purification also removes organic materials, like asbestos particles, microbes, and pesticides, resulting in purer water.

There are several common treatment systems for water purification:

Filtration

In addition to the filters mentioned above, purified water also passes through micro and ultrafiltration systems, which further remove small particles.

Nanofiltration is yet another type of filter that water is passed through during purification. Innovations in new nanomaterials are proving very effective for various treatment methods.

Reverse osmosis 

Reverse osmosis is a standard water purification method. Although technically a type of filter, reverse osmosis uses special membranes with very tiny holes to separate the dissolved minerals and particles from the water. A reverse osmosis filter has pore sizes of about 0.0001 micron. There are several types of these membranes used for purification, each most effective against a different set of water contaminants.

Reverse osmosis can remove up to 95% of organic and inorganic material but is not very effective against some gases with high vapor pressure, like hydrogen sulfide or radon. Certain pesticides and solvents also can't be removed through reverse osmosis. Furthermore, the process can produce substantial amounts of wastewater.

Distillation 

Distillation is another water purification method, though it’s usually not a home treatment. The process involves boiling and evaporating water to first kill the bacteria. The water then turns into steam and separates from the contaminants, particles, and metals. Next, the steam is cooled and distilled into a new container to produce pure or distilled water.

Distillation effectively removes 99% of unwanted compounds from water. But it can also remove some oxygen, resulting in water that may taste flat.

Deionization

In a way, the deionization technique for purifying water is the opposite of distillation. This is because distillation removes water and separates it from the particles, whereas deionization removes minerals and contaminants and separates them from the water. This purification method uses an ion exchange, which involves charging the atoms with positive and negative electricity and removing them through a chemical process.

This method is also sometimes called water softening. 

Ultraviolet disinfection 

The final standard system for purifying water is ultraviolet disinfection. This method of water treatment uses ultraviolet (UV) light and wavelengths to sterilize and disinfect water by reducing the number of bacteria present. You can buy UV water purifiers to use at home or when traveling or camping.

Many contaminants in water are hazardous to your health, and drinking purified water can help avoid them entirely. Compared with water filtration, water purification removes the vast majority of waterborne contaminants, which results in cleaner and purer water.  

The Environmental Protection Agency (EPA) has limits on over 90 contaminants that you would commonly find in water. However, in the US, individual states are free to regulate their own water supply as long as the minimum standards are met. This simply means that the quality of water can vary from place to place.  

That’s why drinking purified water can help make sure that heavy metals like copper or lead — which are both very dangerous as ingesting them is linked to several diseases — don’t enter your body.

Purifying water also removes chlorine, which has been linked to the development of bladder and colorectal cancers. 

Distilled water, free of bacteria and pesticides, is also recommended for anyone with a weakened immune system or certain cancers.

One of the drawbacks of drinking purified water is that many beneficial minerals are removed in the purification process. Unless the nutrients are introduced back into the water, drinking only purified water means that your body may not get enough of certain minerals it needs to function.

In addition to what we already mentioned, water purification also removes essential minerals like:

• Calcium
• Magnesium
• Potassium 
• Sodium
• Zinc

Fluoride is yet another mineral eliminated by water purification. Many countries add fluoride to their water because it’s known to help prevent and reduce the risk of dental decay. Even though high levels of fluoride can pose some danger to your health, there is plenty of evidence showing the upsides of fluoride intake. Those who exclusively drink purified water will need to take this into consideration. 

Finally, whether water purification occurs at home or on an industrial scale, the treatment systems can be costly and require a lot of maintenance.

You can purify your own water at home.

In addition to traditional water filtration, there are also water purification systems that you can install in your home. Some systems are point-of-use (POU) treatment methods, whereas others are point-of-entry (PUE) systems. 

POU systems purify the water you drink or use to cook, and PUE treats all the water that enters your home. If you're interested in buying a purification system, knowing the difference can help you make the decision that’s best for you.

There isn’t an easy way to pick one. If the water has been appropriately filtered or purified, it’s safe to drink.

Understanding the differences between filtered and purified water is essential, but we can’t say that one is definitely better than the other. Deciding which is best for you will depend on individual taste, preference, and circumstance.

Whether you choose filtered or purified, water remains an essential element for life, and drinking enough of it will continue to provide many added health benefits, like  clearing acne,  lowering blood pressure, and promoting skin hydration.