Water is easily one of the most important things in our lives. We need it to survive, but that’s not all. It’s what we use to make a cup of tea, what we drink when on a hot summer’s day, what we sigh under in a hot shower after a long shift at work.
Most of us are fortunate to live in circumstances where the water that enters our home is “potable.” But, by most standards “potable” simply means fit for consumption. But simply being “fit for consumption” is a rather low standard… at least according the EPA.
We want our families to have the best (and we want the best for ourselves, no doubt)! Water filtration technology brings us water that’s so much more than just “fit for consumption.”
Water filtration and purification technology removes contaminants that make our water taste and smell bad, damage our hair and skin, and can even make us ill.
Of course, water filtration and purification technology doesn’t refer to just one process that makes water “better.” There are many different methods used to remove contaminants, and many different ways in which these can be applied. The following is a comprehensive overview of methods and the systems used to implement them, so that you can find the right filtration and purification solutions for the water in your home.
Water Treatment Methods
There are a number of technologies used to filter, treat, and purify water. Each has its pros and cons, and its own particular purpose. Because their efficiency and effectiveness vary in so many ways, many systems use combinations of this technology. For example, an under-sink reverse osmosis water filter might have an activated carbon component to reduce chlorine, as reverse osmosis alone isn’t effective for that task.
It’s important to know what each type of filtration does and how it functions, however, because then you’ll be able to determine what water filtering or purification solution you need. It’s a good idea to have your water tested, either by your local water quality office, by a reputable business, or by using an in-home test kit. That way, you’ll know what levels of dangerous or undesirable contaminants you have in your water, and which filtration methods you should prioritize.
We’ve compiled this list of the most commonly used filtration, treatment and purification technologies with that in mind. We’ll include a bulleted list of what they do and do not remove, and we’ll go into more detail into their strengths and weaknesses, as well.
Note: Please, however, consider this information to be general. Whenever you purchase a particular water filtering, treatment, or purification system or filter, you should review its NSF certifications for yourself. NSF International certifications are a good guideline for knowing what a particular filter or system is actually capable of removing from your water.
Before we explain reverse osmosis (RO), let’s talk about osmosis:
When two liquids of different concentrations are separated by a semipermeable barrier, and each have a different concentration of soluble substances, they tend to equalize.
Whereas osmosis is all about concentrations evening out, reverse osmosis is about one side becoming more concentrated than the other. All (or most) of the soluble substances are drawn out of one side and into the other.
When reverse osmosis is used as a water treatment method, the end result is one side of the barrier (the highly concentrated side) being considered wastewater, while the other side is purified.
Reverse osmosis is very effective at removing many minerals from water, and some chemicals. This can be problematic, however. Some level of mineralization is desirable in drinking water.
RO removes not only harmful minerals, or excess minerals, but practically all minerals. That includes minerals humans need and that occur naturally in water, like magnesium and calcium. And while it can remove some chemicals, there are many man-made chemicals which RO is ineffective against.
Finally, there are some concerns about the efficiency of using reverse osmosis filters. There is considerably more backwash (discharged waste water) produced than there is filtered water. In most set ups, this backwash (which could be as high as five gallons to one gallon of pure water) is discharged into the sewer system. This results, over time, in more unusable water, as sewer treatments themselves are not 100 percent efficient.
Conservationists and those looking to live a “green” lifestyle find this troubling, especially as the discharge water is often still well within safety guidelines for drinking and cooking.
Newer RO systems might utilize a “zero liquid discharge” technology, which involves other filtration methods to further purify the water and return it to the water system. This is usually only practical at the industrial level.
Other new systems, in an attempt to make reverse osmosis filtration more environmentally friendly, allow for the collection of the discharged backwash, which can then be used for purposes other than consumption.
Activated carbon removes a number of undesirable substances, but doesn’t affect the water itself. Essentially, contaminants “stick” to the carbon, allowing the water to flow past. This process is called “adsorption.” It’s called activated carbon because it has a positive charge, which aids the adsorption process.
Activated carbon can be created from any number of different materials, so long as they are organic and have a high carbon content. Materials with a high carbon content are known as “carbonaceous” materials. These include coconut shells, wood, coal, peat, and the shells of nuts.
Coal is the most common source material for activated carbon, while coconut shell carbon is believed to be one of the most effective types. It’s also relatively more expensive.
Activated carbon also comes in different forms:
- Granulated Activated Carbon (GAC)
- Carbon Blocks
- Catalytic Carbon
Most in-home water filters use granulated activated carbon or carbon blocks.
GAC filters are usually best for simple chlorine removal, although they can be engineered for other uses as well. Carbon block filters have the same (or improved) chlorine removal feature, but can also be effective at removing sediment and other contaminants which a typical GAC filter would be unable to handle.
Catalytic carbon is seen more rarely, simply because it is a newer and more advanced carbon application. It’s best known, in terms of filtration, for its ability to remove chloramines from drinking water—something GAC and carbon blocks can’t do as well.
However, we are starting to see catalytic carbon’s inclusion in more in-home water filtration systems. Typically, it appears in multi-stage systems with standard activated carbon (granulated or in blocks) as another stage of filtration.
Through the process of adsorption, activated carbon removes contaminants like chlorine, volatile organic compounds, and radon. It’s this method’s ability to remove chlorine that makes it so popular. Chlorine negatively affects the taste of our water, but it is not generally considered a “contaminant” by regulators… so it’s up to us to reduce it at home.
Activated carbon also removes the majority of human-made chemicals like methyl-t-butyl-ether (MTBE). MTBE is found in gasoline. However, activated carbon may not be effective when it comes to most organic substances, sediment, nitrates and related ions, or some heavy metals.
When you’re choosing a carbon filter, it’s especially important to look at the NSF rating of the particular filter. That’s because while activated carbon alone may not be effective against some contaminants, clever engineering can make these filters capable of much, much more.
Distillers work by converting water into steam via heat—i.e. they boil the water. Once the water becomes steam, the steam is collected and cooled, converting it into water again, water which is now purified.
Distillation can remove bacteria from water, and minerals. Like reverse osmosis, however, it is not very effective against chemicals and demineralises water indiscriminately, removing helpful minerals as well as undesirable ones.
Finally, distillation is not very efficient, either from an energy-use perspective (a great deal of heat is required for the process) or from a resource perspective (five gallons of water can be lost just to purify one gallon).
Because of this, distillation is generally used to produce water specifically for scientific purposes (when mineral and bacteria free water is required), and in developing countries with plentiful access to water that is likely to have bacteria contaminants. It has very few in-home applications in a developed country.
Ultraviolet (UV) water treatment uses specialized lamps that emit high amounts of a particular wavelength of radiation. (In this context, radiation just means “radiated energy.”)
It’s part of the electromagnetic (light) spectrum, just like visible light is, but it’s not visible. We call it ultraviolet, or ultraviolet light.
Ultraviolet light is the “hottest” part of the light spectrum. You’ve probably had a run in or two with it yourself via having a sunburn, and you are likely also familiar with the correlation between UV light and skin cancer. That’s because UV light affects organic materials and DNA.
Well, with UV water filters you can put UV light to work for you, by turning that power on bacteria, mold, algae, and a variety of microorganisms that might be in your water.
However, ultraviolet light does not do anything to mineral, sediment, or chemical contamination. Ultraviolet treatment is used in combination with other methods for this reason.
It is very important, however, in areas where potable (drinkable) water is scarce due to the risk of disease, and some portable options for UV water filtration have also been developed for campers and travelers.
Water softeners rely on a process called “ion exchange,” where water passes through beads coated with “soft” minerals (typically sodium and potassium). The “hard minerals” in the water, like calcium and magnesium, stick to the beads.
Water softening is not generally necessary for municipally treated water, and can actually be harmful, as it might result in the removal of too many helpful minerals. Magnesium and calcium are not, in and of themselves, undesirable.
Water softening only requires the removal of hard minerals, but is often combined with activated carbon filtration and sediment filtration as well.
However, for well water systems, the levels of calcium and magnesium may be so high that they result in mineral build up that can disrupt the function of shower heads and other water fixtures, and leaving an unattractive residue. “Hard” water also makes it more difficult for soaps and detergents to lather.
Water softening can be controversial, due to the fact that it adds additional sodium or potassium to water. Some sources believe the amounts added are inconsequential to healthy persons, while others are less confident that this is the case.
If you’re concerned about the levels of sodium or potassium in your drinking water post-softening, you can always get it checked! Many areas offer free water testing.
Point of Use System Types
There are as many different water filtration system types and forms as there are methods, believe it or not!
“Point of use” refers to systems that filter the water at the point when you’re using it. Rather than filtering all water that enters your home. For example, a faucet mounted filter only filters the water from that faucet, a shower head filter only filters the water flowing through that particular showerhead, and so on and so forth.
Here are the most common point of use in-home system types, along with an overview of their pros and cons, so you can decide which best suits your needs and lifestyle.
For some people, just one point of use system is sufficient. Others might want a combination of several systems.
These water filters are mounted under your counter/sink, as the name “undercounter mount” implies. Most under counter mounted water filters make use of activated carbon. However, there are a few that use reverse osmosis filtration (and are usually advertised as such).
There are even under counter mounted UV treatment options, intended for water sterilization. These are typically in medical or scientific institutions, rather than homes, however.
Undercounter mounts that use activated carbon are usually referred to as “standard” filters, as opposed to RO. They can be exceptionally helpful for removing chlorine that gives water a bad taste, as well as man-made chemicals.
These water filters are great for those who have water that is already treated for sediment, heavy metals, and so forth (as municipal water typically is) but would like their water to taste better.
They’re also useful if you are concerned about pesticides or other chemicals in your water. Having them placed under the sink means that they don’t take up your valuable counter space, and that the filters are kept out of sight.
However, for those whose cabinet storage space is at a premium, or who are unconcerned about the aesthetics of visible water filter, there may be better options.
Personal Water Bottles
Personal water bottles are a great way to save money and help the environment by not producing a lot of wasted plastic, which is why so many people are choosing them over bottled water from the store.
But what if you don’t have access to filtered water, or your tap water isn’t pleasant to drink?
That’s where personal water filter bottles come in.
The vast majority of personal filtered water bottles utilize activated carbon filters. However, some use UV treatment.
Carbon filtered personal water bottles are generally for people on the go whose tap water simply doesn’t taste great. They’re handy as a portable option, but not very practical for filtering water for an entire family’s use, nor very convenient for singles or couples when they are at home.
College students and roommates with limited fridge space, however, may happily embrace a personal filtered water bottle as one of the only practical ways to get fresh tasting water easily and cheaply.
UV filtered personal water bottles are helpful for campers and those who live in areas where they might not have potable water due to bacterial/microorganism contamination. Because UV light doesn’t affect other contaminants or sediment, some UV personal filtered water bottles are compatible with additional “pre-filters” that can address these other issues.
As their name suggests, faucet mounted water filters are attached to your faucets themselves. Basic models rely entirely on carbon filtering. However, some more advanced models also have sediment pre-filters and even re-mineralizing components to add natural minerals back into your water.
Faucet mounted water filters are an exceptional choice for those with very limited storage space, and who want the convenience of filtered water straight from their tap.
These devices do however have a few downsides. They have relatively small filters, obvious visibility in the kitchen, and the difficulty of finding one compatible with anything but a standard sink. They also tend to lower the water pressure from the faucet they’re attached to.
Most pitchers use activated carbon filters, which are installed in the top of the filter. Some also have ion-exchange filters which work on the same principle as water softeners, to remove heavy metal ions.
Water filter pitchers are convenient for single people and couples with significant refrigerator storage, but they may not be enough for families. Because the filters are relatively large, the size of the pitcher is disproportionate to its water capacity, so having multiple pitchers might not be ideal.
Even when taking time between refills in account, most can only filter about 2 gallons per day efficiently and effectively.
Pour Through Filters
Pour through filters, are essentially a self contained filter and container. You simply pour unfiltered water in… and when you’re ready you pour filtered water out.
As water passes into the storage chamber, it passes through an activated carbon filter (in standard models). More advanced models can also contain catalytic carbon filters, sediment filtration, and mechanical filtration (used to capture sub-micron particles like asbestos).
These filters take up a lot of space on one’s countertop, so they’re not recommended if space is particularly limited—or if you don’t think their appearance suits your kitchen’s décor. However, unlike faucet mounted and under-sink models, they don’t require hardware installation, nor are they a hassle to move out of the way.
As the popularity of bottom-freezer and side by side refrigerators continue to grow, it’s become more common to see in-door water dispensers in refrigerators.
Like many focused filter solutions, these filters primarily use activated carbon as the filtering method.
They score high points for convenience: they don’t disrupt the look of your kitchen, filtered water is always available, and they don’t impede either counter or cabinet space. While they do take up some room (by having less interior refrigerator space), it’s often less than you’d expect from a pitcher—and they’re much better for a family.
That doesn’t mean they’re everyone’s perfect solution, however, because of cost. Refrigerators with this built in option are more expensive than their counterparts. But perhaps more importantly, statistics show that they need maintenance more often. This may be too much hassle for singles or those who are pinching pennies.
Shower filters connect between your water source and your showerhead. Their primary purpose is to remove chlorine from water, and/or to soften water. As a result, shower
filters are generally activated carbon based. They may also contain kinetic degradation fluxion (KDF), or a combination of KDF and activated carbon filter technology.
Some shower filters also contain water softeners. Finally, there is a relatively new filtration method known as Vitamin C filtration. This new technology helps to reduce chloramines in showers.
Chlorine and minerals in your shower water can lead to limp and dry hair, dry skin, dandruff, and skin irritation.
However, it’s important to note that the heat of shower water can impede the effectiveness of filters. Have your water tested pre- and post-filtering from the shower to see if you’re getting the results you want.
Point of Entry System Types
Point of use systems, like those discussed above, address your filtration needs right when you need water from one particular source—this faucet, that pitcher, etc. However, point of entry system types, which we’re about to discuss, filter your water as it comes from the original source, so that all of the water in your home is filtered.
Typically, point of entry systems connect at the main line as it enters the house, prior to its connection to your water heater. This means that every faucet, every showerhead, every washing machine, and every toilet in your home has treated water.
These are also known as “whole house” filters. And yes, you guessed it—there are multiple types! We’re going to discuss point of entry systems in terms of filtration method, but keep in mind that many systems use combinations of filtration method.
Whole House Reverse Osmosis
Because of the impressive list of contaminants that reverse osmosis technology can remove, some people opt for a whole house system that includes RO filtering. However, these systems aren’t the most practical solution for every home.
Most homes are not receiving water with the levels of TDS (total dissolved solids) that would make a reverse osmosis system worthwhile, unless they have particular health concerns. Some exceptions include coastal homes, which may have brackish water with high levels of dissolved sodium from seawater. Homes with well water may also have high TDS levels that would make a whole house RO system appealing.
Their efficiency at removing minerals like calcium and magnesium can result in water with a harmfully acidic pH, which may prompt some homeowners to resort to a system that also remineralizes water.
Finally, reverse osmosis systems on their own cannot remove chorine, so they must be combined with activated carbon filtration.
RO whole house systems are primarily suited to homes with medical concerns or incoming water with high TDS levels.
Whole House Chlorine
Whole house chlorine removal systems, which rely on various types of activated carbon filters, are the most popular choice for most families. That’s because most homes receive incoming water which is low in dangerous contaminants, but might be high in chlorine—and chlorine is often to blame when we have bad tasting water.
Because these systems are common and have been in development for decades, there are also very affordable versions.
UV Whole House Systems
As we’ve discussed previously, UV water treatment is essentially used to disinfect your water, so don’t expect these whole house systems to do much more than that. Of course, like other water filtration systems, they can (and usually should) be combined with other filtration methods.
It’s especially important to pre-filter water before UV sterilization if it’s high in TDS. That’s because some contaminants can absorb UV, not letting it transmit through the water to kill bacteria effectively.
Those who receive well water may be at a higher risk of microbiological water contamination, and this contamination could result in illness. That’s especially true for children, the elderly, and those with other medical conditions.
But even municipal water can contain dangerous bacteria, because some types are resistant to chlorine, like giardia, and a whole-house UV disinfection system can help with that.
Whole House Water Softeners
Whole house water softeners are intended for homes receiving water with excessively high amounts of “hard” minerals. Primarily those minerals like calcium and magnesium. This usually applies to homes that rely on well water. Water softener systems aren’t designed for filtering other contaminants out of your water. So, the water entering the system should be pre filtered for contaminants like sediment, at the very least.
Some water softener systems do include a pre-filtering process, and these are sometimes referred to as water conditioning systems.
Some municipal water systems do indeed have hard water. If you notice calcium deposits around your faucets, that is a good indicator of hard water. Another is if water tends to stain your sinks, showers, and toilets. Buildup from hard water can even cause reduced water pressure. If you have hard water, there are myriad reasons to take action and treat it with a softener.
While a whole house water softening system might seem like a large investment. But, it saves a great deal of time when it comes to cleaning. Water softeners also provide water better suited for bathing, drinking, and cooking. And, perhaps their biggest “pro” they reduce wear and tear on your plumbing system.
When you pour a glass of cold water from the tap in your home, are you satisfied with it? Do you feel that it’s safe for your child? Does have an unpleasant smell or flavor that makes you reach for a can of soda instead?
Clean water is required for us just to stay alive. Beyond that, we want to trust that the water entering our homes is clean and safe. But that’s not always the case. Many municipalities have far less stringent water treatment programs than might be considered reasonable.
In many others, even if the water is “safe” medically, it tastes or smells unpleasant. That leads us to avoid drinking water, which compromises our health. Or, perhaps we buy bottled water, which compromises our financial resources and the environmental well-being of the planet.
Whether you’re a college student that just wants a personal water bottle for class because the tap in your dorm’s common room smells like the community pool, or a single mom wants a faucet mounted filter so her kids will drink from the tap, or a cabin-dwelling lumberjack that needs a whole house water softener so that he can take a proper shower, there’s a solution out there for you and your family.