There are lots of types of water filtration products on the market today, many staking the claim of being the one and only filter you’d ever need.
While it is certainly possible to have a single filtration system that provides all your purification needs, the various types of purification methods make it difficult in identifying what those needs are.
Granular activated carbon and 6-stage reverse osmosis sound like they’d get the job done, but what do they actually do? And the options between pitcher filters, countertop filters, under-the-sink filters, and whole house filters only add complexity to the decision-making process.
The truth is, selecting the right water filtration system for your home isn’t very difficult. It just requires an understanding of what you need it for.
This article will explain how to identify what harmful contaminants may be present in your water source and how to choose the best filtration system based on your needs.
We will cover:
- Types of contaminants
- Main water sources
- Types of water filters
- Sediment filtration
- Activated carbon filtration
- UV purification
- Reverse osmosis
- Water softening and water conditioning
- Iron, manganese, and hydrogen sulfide treatment
- Whole house filters
|Filtration Method||Type of Contaminants Removed||Best used for|
|Sediment||Physical||Well Water, Rainwater|
|Activated Carbon||Chemical||City Water, Well Water|
|UV Light||Biological||Well Water, Rainwater|
|Reverse Osmosis||Chemical, Biological||City Water, Well Water, Rainwater|
|Softener / Conditioner||Chemical (calcium, magnesium)||City Water, Well Water|
|Iron Filter||Chemical (Iron)||Well Water|
|Whole House||Physical, Chemical, Biological||City Water, Well Water, Rainwater|
What exactly are we trying to filter out?
The first step in choosing the right filtration system is to understand what exactly it is we’re trying to filter out. There are four classifications of contaminants according to the CDC and EPA.
They are physical, chemical, biological, and radiological contaminants.
Physical contaminants refer to sediment, silt, or any type of debris that may be naturally present in the water supply. These contaminants are primarily found in groundwater due to the layers of rock that must be drilled through. Surface water such as lakes and rivers may also have a high concentration of sediment and silt.
While large physical contaminants can be harmful if consumed, they’re more of a concern for the water system as they can cause blockage and damage to water pumps and filters.
Physical contaminants must be “blocked” before entering the drinking water supply and this is typically done through a pre-filtering process.
Chemical contaminants are usually the most common type of contaminant due to their broad category and refer to anything of an elemental or chemical make-up. These can be as simple as an element on the periodic table such as chlorine, nitrogen, arsenic, and fluoride, or as complex as herbicides, pesticides, VOCs, and pharmaceuticals. Chemical contaminants can also refer to heavy metals such as lead and mercury.
These types of chemicals can cause long-term sickness if consumed. Arsenic is known for causing cancer and skin lesions while lead and mercury can cause neurological and developmental problems (WHO).
Chemicals are best removed from the water supply through the adsorption of a high-affinity medium such as activated carbon. Because chemicals vary in molecular size, several layers of filtration are often required for completely removing the entirety of harmful components.
There are some elements that are naturally present in water and aren’t necessarily harmful if consumed. Elements such as calcium and magnesium, quite common in groundwater and lakes, are actually beneficial for human consumption. However, high concentrations of these elements can be damaging to the plumbing system. We’ll get into how water softening can help remedy this, later.
Biological contaminants are perhaps the most concerning of all contaminants as the consequences of consumption are most dire. These refer to bacteria, viruses, and parasites that may be present in the water, and the conditions that arise from them are known as waterborne diseases.
Biological contaminants are most common in stagnant water sources, water sources exposed to human or animal feces, and countries with poor water treatment services.
Bacteria - The most common biological contaminants include Typhoid, Cholera, E. coli, Salmonella, and Legionella. While symptoms among these diseases vary, untreated conditions can lead to death.
Viruses - The most common viral disease found in water is the Norovirus, also known as Traveler’s Disease, and is typically transmitted when someone drinks from a foreign water source.
Protozoa - Finally, parasites such as Giardia and Cryptosporidium are commonly ingested when drinking from a water source where infected animals have defecated.
While carbon filtration can block some of the larger bacterial entities, viruses are usually small enough to pass through the filter block.
Chemical disinfection through chlorine or iodine can kill bacteria and viruses in varying time frames. Parasites can be killed in a much longer time span.
Boiling water is also an effective method for killing biological contaminants, though also isn’t the quickest of methods.
The most effective method for eliminating all biological contaminants is through ultraviolet radiation. UV purification almost instantly renders all bacteria, viruses, and parasites completely harmless, making contaminated water safe to drink.
Read our guide on UV purification for home use to learn more.
The least common of contaminants are radiological or radioactive contaminants. These refer to unstable elements such as plutonium and uranium that may have been emitted due to nuclear radiation. While rare enough to not bear much weight when deciding on which filter to purchase for your home, it is worth recognizing nonetheless.
The most effective method for removing radiological contaminants is a combination of carbon filtration and reverse osmosis (Forbes).
Where does your water come from?
How and where your water is sourced has a significant effect on the potential contaminants you may come into contact with, which then affects the type of filtration process you should use. Here's we'll cover the most common sources for residential water.
Municipal water services
Most municipal water sources in the United States come from either groundwater via a large well or surface water via a dam or reservoir. These public water sources are treated by the city via a process of flocculation, sedimentation, filtration, and disinfection (CDC).
Flocculation and sedimentation remove all physical contaminants such as debris, silt, and sand.
The filtration process involves layers of carbon for removing MOST, not ALL, of the dangerous chemical contaminants in the water.
The disinfection process then kills all biological contaminants that may be present.
It is important to note that while public water treatment does remove most of the harmful contaminants, the filtration process for chemical contaminants is very basic. It is recommended that households still perform their own filtration process to further remove chemical contaminants that may have slipped through the initial carbon filter.
Heavy metals such as lead and other chemical compounds such as herbicides and pharmaceutical drugs can still be found in tap water.
Private wells and community wells
Groundwater is an excellent water source due to it being naturally filtered by the earth’s crust. While biological contaminants aren’t as common in groundwater as it is in surface water, physical contaminants such as sediment and rock will certainly need to be pre-filtered out. A high concentration of naturally occurring chemical elements such as magnesium, calcium, and iron may also be present (USGS).
Those who rely on a private or community well should have a sediment pre-filter for physical contaminants and possibly a UV filter for any potential biological contaminants. To remedy the high concentration of hard water and iron, a water softener, water condition, or iron filter may be needed.
Read our guide on well water pumping to learn more.
Rainwater harvesting can be a very useful means for supplementing a household’s existing water supply. While typically used for outdoor gardening purposes, it is possible to filter rainwater for drinking.
Rainwater, typically caught by a large catchment system such as a roof, can contain physical and biological contaminants. Debris such as twigs and dirt as well as animal feces and algae are often present in rainwater and therefore must be filtered out.
Many rainwater filtration systems consist of a UV filter and activated carbon combination.
Learn how to filter rainwater from our guide.
Some off-grid cabins source their water from a lake or river via a water pump. Surface water often contains physical, biological, and chemical contaminants and therefore must be treated for such. In most cases, a reverse osmosis system will treat surface water for all of its harmful contaminants, making it safe to drink.
Now that we've covered the different sources for water and the possible contaminants present in each, let's get into the best types of filtration for each scenario.
Sediment filters, also known as pre-filters, are usually the first line of defense in a water purification system. Sediment filters are designed to prevent physical contaminants such as debris, sand, and rust particulates from coming into contact with the rest of the filtration system.
The reason for this is that large particulates can either cause damage to certain filters or reduce their effectiveness. Physical particles can cause damage to a reverse osmosis membrane and can prevent UV filters from completely eliminating microorganisms from the water (Freshwater Systems).
Many water purification systems will have a pre-filter built into their existing system. For example, a 5-stage RO system typically has a sediment filter as its first stage.
Because sediment filters are designed to filter out larger physical contaminants, chemical and biological contaminants are still small enough to pass through the barriers. Thus, further filtration is needed to remove them.
Recommended Sediment Pre-filter: Springwell Spindown Filter
The Spindown Sediment Filter by Springwell is a great choice for those with heavy sediment in their well system. The 100 micron mesh screen will block out large particles and is easy to remove for cleaning.
- 100 microns
- 25 GPM
- 1" in/out
The main function of the activated carbon element is to filter out chemical contaminants.
And for this function, carbon is an incredible medium for it.
Carbon filtration works through a process called adsorption. As opposed to absorption which merely soaks up chemicals similarly to how a sponge soaks up water, adsorption binds chemicals to the surface area of the carbon elements via ion exchange.
The reason that this works so efficiently is that activated carbon has an extremely high surface area for chemicals to bind to. In fact, one gram of activated carbon has over 32,000 square feet (3,000 square meters) of surface area (Carbonblocktech). That’s a lot of room for chemical elements to bind to.
And the list of chemical contaminants that activated carbon is responsible for filtering is quite long. Depending on the pore size of the activated carbon filter, the contaminants that can be removed include chlorine, herbicides and pesticides, mercury, VOCs such as gasoline and solvents, and hydrogen sulfide. By removing these contaminants, activated carbon filters are also able to significantly improve the taste and smell of the water.
GAC vs Carbon block
There are two main types of carbon filters used in residential applications, GAC and carbon blocks.
GAC refers to granular activated carbon and refers to carbon that has been reduced to a loose, granular form. GAC filters have a high flow rate as water is able to pass through quite freely.
A carbon block is comprised of the same material but is much more compacted and thus more efficient in the filtration process. Because there is more surface area, a single carbon block can filter through a higher volume of water before needing replacement as opposed to GAC filters. The downside to carbon blocks is that the flow rate is significantly lower.
What doesn’t it remove?
The filtration capability of an activated carbon filter is determined by its pore size, measured in microns. Pore sizes for activated carbon blocks can range from as large as 50 microns down to 0.5 microns.
This is precisely why activated carbon filters are so efficient at filtering certain chemical compounds but not dissolved solids and biological contaminants. Bacteria and viruses and elements that cause hard water such as calcium and magnesium are small enough to slip right through the carbon filter’s pores (WQA).
What is carbon filtration best used for?
While municipal water services do use a form of carbon filtration for treating the city’s water supply, it’s usually in the form of GAC filtration with larger pore sizes. This is due to the large volumes of water that need to be processed daily and the high flow rate that they’d need to maintain.
And while many of the harmful contaminants may have been removed at the city level, it is not at all uncommon for contaminants such as lead, mercury, and traces of pharmaceutical drugs to come through the tap.
Homes that rely on city water will benefit greatly from installing an activated carbon filter at the point of entry to their home’s water supply.
Recommended Carbon Filter: Crystal Quest Alkaline Countertop
The Alkaline Countertop Filter by Crystal Quest is a 7-stage carbon filtration system that removes much more than most standard carbon filters. The GAC filter alone removes most chemical contaminants upfront.
With a 1 micron pre-filter, GAC filter, and ion exchange, this combination filter also removes sediment, Giardia & Crypto, and heavy metals such as lead and aluminum.
The ion exchange portion improves taste and increases alkalinity.
- Sediment pre-filter
- GAC carbon filter
- Ion exchange for increased alkalinity
- 5.5"L x 13.5"H x 5"W
- Built to last for years
The most concerning contaminant that may be present in water are generally biological contaminants, mainly due to their potential for causing humans to get very ill. And the most effective method for eliminating biological threats such as bacteria, viruses, and protozoa, is ultraviolet radiation.
UV purifiers use high-frequency radiation to penetrate the membrane of microorganisms, essentially killing them. In fact, UV purification is so effective that it’s been used by municipal water suppliers and commercial water bottling plants for decades.
How does it work?
Residential UV purification systems contain an ultraviolet bulb and ballast that comes into contact with the water supply as it passes through. Any organism present in the water will come into contact with the powerful UV light, resulting in its DNA being disrupted (APEC).
What is UV purification best used for?
UV purification systems are best used for water sources that aren’t previously treated for biological contaminants, such as rural homes relying on well water or river water, or rainwater harvesting systems.
Important things to consider
It is important for UV systems to have a sediment pre-filter in place at the front end of the water supply. Water that is high in sediment can reduce the effectiveness of UV purification. This is because particles can block some of the UV rays and allow microorganisms to pass through. UV purification works best when the water is as clear as possible.
It is also important to note that while UV purifiers eliminate the threat of biological contaminants extremely effectively, it is the only thing they will eliminate. UV purifiers themselves won’t eliminate any physical or chemical contaminants. For this reason, a UV purifier is best paired with another filtration device such as activated carbon.
UV filters require electricity and will need the bulb to be replaced occasionally.
Learn more about UV purification systems from our guide.
Recommended UV Purifier: Acuva Arrowmax 2.0
The ArrowMAX 2.0, eliminates up to 99.9999% of all microorganisms including viruses, bacteria, and protozoa. Acuva's smart faucet indicates when the UV is activated.
With a flow rate of 2 liters per minute, the ArrowMAX 2.0 is capable of sustaining a high flow of clean, drinkable water consistently. It’s assembled in a high-quality polymer casing with a stainless steel UV reactor.
- Flow rate: 2 liters per minute
- Max PSI: 100
- Dose Delivery: >16 mJ/cm²
- Certification: NSF/ANSI-55
Reverse osmosis technology is a modern marvel that has truly revolutionized the water purification industry. Whereas the previously mentioned purification systems have a specific type of contaminant that it is best capable of removing, RO systems can essentially remove them all.
It’s widely used in residential, commercial, and industrial applications and is the primary technology behind desalination and wastewater treatment.
How does RO work?
What makes an RO system special is the semi-permeable membrane through which everything must pass. Earlier, we mentioned the idea of pore size playing a significant role in deciding which contaminants can pass through a filter. While activated carbon filters can have a pore size as small as 0.5 microns, an RO membrane has a pore size of 0.0005 microns. With a pore size that small, essentially only water molecules will pass through (Freshwater Systems).
So, as contaminated water is pressurized through the membrane, all of the contaminants are blocked while pure H20 comes out the other side.
An RO membrane is quite sensitive to other contaminants though, as sediment and chlorine can damage the membrane. Thus, sediment and activated carbon blocks are often included as part of the entire RO system design.
Additionally, pure H20 without the presence of beneficial minerals such as magnesium and calcium can often taste flat. So, post-filters are also often included as a way to improve taste.
What is RO best used for?
Because RO systems are capable of removing contaminants of all categories, they’re appropriate for almost all settings. RO systems can improve the taste and remove heavy metals from city tap water. It can also ensure that the well water source a rural cabin relies on is free of arsenic. And those pumping water from lakes won’t need to worry about the presence of Giardia.
Important things to consider
As effective as RO systems are, there are a few considerations that should be accounted for.
Because of the many stages and filters, an RO system forces the water to go through, flow rate can be much slower as compared to a GAC filter, for example. Some RO systems have managed to improve flow rate significantly but it is still widely considered to be on the slower end of most filtration systems. To remedy this, some homeowners include a pressure tank to store the purified water for later use rather than waiting for the system to undergo the filtration process every time the tap Is turned on.
With many cartridges come many parts to replace. Most of the filters won’t need to be replaced until the 6 months to 12-month mark, but one would need to keep track in order to keep proper maintenance.
RO systems can range from 500 to 2000 depending on the size of the system.
Learn more about home RO systems from our guide.
Recommended RO System: Waterdrop G3
The Waterdrop G3 is one of the most efficient residential RO systems available. Where most RO systems provide a 50 GPD flow rate, the Waterdrop provides 400 GPD, that's 1 cup of water every 12 seconds.
The seven-stage filtration system includes a pre-sediment filter, a post-carbon filter, and 3-layer reverse osmosis membrane, all responsible for removing chlorine, sand, rust, solids, and other impurities.
- Smart TDS monitoring panel
- 400 GPD Fast Flow
- 1:1 Low Drain Ratio
- 7-stage Filtration
- Automatic Flushing
Water Softener / Conditioner
Water hardness is the condition of having an overly concentrated presence of naturally occurring minerals such as calcium and magnesium in the water supply. While these minerals aren’t necessarily harmful if consumed, having an excess amount can cause damage to the plumbing, causing calcification of the pipes and faucets.
Water softening works through a process called ion exchange. As hard water passes through the resin tank, sodium ions bind to the water molecule, replacing much of the calcium and magnesium originally in the water. “Softened” water then passes through the system and into the water supply (Freshwater Systems).
A second tank is used to replenish the now “hardened” resin beads, making room for more hardened water to be processed. This regeneration cycle repeats until fresh salt needs to be added as routine maintenance.
Water conditioning, also known as “salt-free” water softening, shares the same goal as traditional water softening but with a different process. Rather than reducing hardness through the ion-exchange process, water conditioners use a material called Template Assisted Crystallization or TAC.
As hard water passes through the TAC media, the calcium and magnesium minerals form crystals which make it much more difficult to calcify onto pipes and faucets.
What is softening/conditioning best used for?
Groundwater typically has a high mineral concentration making well users prone to have hard water. Those who rely on community or private wells can benefit greatly from a water softener or conditioner.
Get a better understanding of water softeners from our guide.
Recommended Water Softener: Crystal Quest
Crystal Quest's Whole House Water Softener comes with pre and post filtration cartridges to remove unwanted contaminants in addition to solving the hard water problem. The ion exchange tank is a 48,000-grain capacity, large enough for a 5-person home. Both pre and post filters remove sediment, VOCs, pesticides, and industrial solvents.
- 3 Stages of Filtration:
- Sediment Cartridge
- Ion Exchange
- Carbon Cartridge
- 48,000-grain capacity
- Service Flow: 9-11 GPM
- 1-year warranty
Iron, Manganese, Hydrogen Sulfide
Like hard water, excessive Iron can cause problems to the water system but in a much different fashion and requires a much different solution.
Iron is also a naturally occurring mineral found in groundwater, making up 5% of the earth’s crust (World Atlas). Thus, it is highly common to be found in well water applications.
Low concentrations of iron generally aren’t a concern, but depending on the type of iron, higher concentrations can give a reddish tint to the water supply, cause deposits that affect flow rate and leave an unpleasant, metallic taste to the drinking water.
What are iron filters best used for?
Ferric iron, ferrous iron, and iron bacteria are all different forms of iron and each requires a different solution. So, conducting a test to determine not only the amount of iron present, but the type of iron as well, is an important step to take before deciding on which iron filter to acquire.
Well owners that notice a metallic taste or a reddish tint to their water may benefit from an iron filter.
Testing for iron can be conducted with a self-test kit or by inquiring with a lab testing service.
Manganese and Hydrogen Sulfide
Where a high concentration of iron is present, manganese and hydrogen sulfide is usually also present. Manganese is characterized by a dark tint appearing in the laundry and hydrogen sulfide is characterized by a rotten-egg smell.
To learn more about how to identify the characteristics of iron, manganese, and hydrogen sulfide in the water, as well as how to properly treat them, be sure to check out our guide on how to remove iron from well water.
Recommended Iron Filter: Homemaster 3-Stage Iron Filter
Homemaster's 3-Stage Iron Filter is great for well owners with a high concentration of iron in their groundwater supply. This unit combines a sediment, carbon, and iron filter into a single system.
The first stage blocks all debris and sediment from entering the system with a pre-filter. The second stage is a radial-flow iron reduction filter that effectively reduces up to 3ppm of iron. Finally, the GAC filter removes additional chemical contaminants and improves taste.
- Iron, Sediment, Carbon Filter
- Ferrous / Ferric Iron < 3 ppm
- Silica < 100 ppm
- Manganese < 1 ppm
- pH > 7.0
- 15 GPM
- 100,000 Gallon Capacity
- 2-year Warranty
- Made in USA
Whole House Filter
When the presence of contaminants varies widely, and when the volume of water needed for purification is large, a filtration system for the entire household may be the appropriate solution.
Whole house filters incorporate multiple filtration systems into a single unit and can handle the volume of water an entire family would need on a daily basis. These all-in-one units make it easier for homeowners to focus on one system rather than connecting multiple filtration systems together.
Components of a whole house filter
Whole house filters can vary in components, but generally, they will include a sediment pre-filter for physical contaminants, an activated carbon filter for chemical contaminants, and a UV purifier for biological contaminants.
Benefits of using a whole house filter
One benefit of a whole house filter is that potentially all possible contaminants will be filtered out without having to purchase different filtration systems individually.
Also, because whole house filters are large, they can handle large volumes of water before requiring filter replacement.
Recommended Well Water Whole House Filter: Aquasana Rhino
For well owners, the Aquasana Rhino is the perfect all-in-one filtration system for the home. At its core, the Rhino is a carbon filter capable of removing chemical contaminants from the groundwater source. The UV filter removes all instances of biological contaminants including bacteria, viruses, and parasites.
The pre-filter removes all physical contaminants before entering the system and the post-filter dramatically improves the taste. Finally, the salt-free water conditioner option will reduce water hardness which is typical for well owners. Altogether, the Rhino takes care of all possible forms of contamination for well water while also reducing hardness.
- 500,000 gallon capacity
- UV Purifier
- Salt-free water conditioner
- Pre/post filter
- 5-year warranty
Recommended City Water Whole House Filter: Homemaster
Self-proclaimed as the "best whole house filtration for city water", Homemaster's 3-Stage Filter provides excellent filtration for all the contaminants that slip through the public water treatment system. A mixed-media GAC filter at the core, the Homemaster filter superbly removes a host of chemical contaminants such as chlorine, pesticides, lead, copper, and significantly improves the often foul taste of city water.
The nano-fiber sediment filter removes fine particles that may clog up the carbon filter and reduce effectiveness. With a 0.2 micron pore size, it is capable of removing biological contaminants such as viruses, bacteria, and parasites. It also reduces some ionic metals such as fluoride.
- 95,000-gallon capacity
- Greatly improves the taste of city water
- Removes biological contaminants
- Removes chlorine, pesticides, and heavy metals
- Reduces fluoride
- 2-year warranty
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