It will be hard enough to find a house without a water filter these days. The filtered tap water ensures the safety of you and your family to a great extent.
That’s why you will find water filters everywhere. But, many of us aren’t aware of what stays inside a water filter. That’s why choosing one for your home or office gets complicated.
Knowledge about the interior of a water filter isn’t necessary. But, it will help you when you buy a new one for your home. A good water filter will serve for years to come.
One very confusing thing about water filters is the number of stages. On one side, you might find 10-stage water filters. On the other hand, there are filters with three levels or less.
In this post, we will be discussing the various stages a water filter can have. Also, we will explore how those work to purify tap water.
As for us, we at Aquaseep try to find you the best household water-related products. To do that, we will give you facts, data, and stats. Now, let’s learn about the various stages of water filters.
What are the primary stages of filtration in a water filter?
There are 5 (five) basic building blocks behind a modern water filter. Any water filter you see today is an ensemble of at least one or more of these stages. Those are-
- Sediment Filter
- Activated Carbon Filter
- Reverse Osmosis Membrane
- Alkaline Water Filter and
- Ultraviolet Ray disinfector
Most water filters consist of the first three stages, while some will additionally feature the fourth one. A water purifier with a UV disinfector is pretty much rare.
Now, let’s find out about those, one after the other.
The First Stage: Sediment Filter
What is a sediment filter?
The sediment filter works as a prefilter to get rid of the dust, rust, clay, sand, and other suspended particles from the water. It stays and performs as the first stage of filtration in any water filter you will find.
The sediment filters come in a cylindrical form with a hollow interior. On the surface, there are multitudes of minuscule pores on it.
On the outside, there is plastic housing. It holds the filter medium consisting of acrylic or glass fiber, ceramic, cellulose, or paper. There is a gap between the housing and the filter medium.
As mentioned earlier, the filter medium consists of a porous formation. Based on its design and working principle, the sediment filter can be of two types.
- Single surface sediment filter
- Graded surface sediment filter.
The single-surface filters consist of a thick sheet of filter-medium. There will be a uniform number of pores inside and outside.
On the other hand, the graded surface sediment filter consists of a filtration stage with variable thickness. The pores on the inside get smaller than those on the outside. As a result, the density of the medium varies as you go inside.
These graded type water filters are now the widely used types of sediment filters these days.
How does a sediment filter work?
Tap water at high pressure enters the sediment filter. The perforated filter medium acts as a barrier. Through the pores, the water molecules can easily pass. But, the suspended particles like clay, dust, rust, and sand particles get trapped.
The sediment filters have a specific micron rating. A micron or micrometer is a unit to measure the dimension of the molecule. According to SI units, one micron means one-thousandth of a millimeter.
A 10-Micron sediment filter will remove suspended particles above 10-micron in size. So, when you check out a sediment filter, you should look out for its micron rating.
The lower the micron rating, the better the filter is for getting rid of the undissolved molecules. The outer portion of the filter medium traps the bigger particles.
On the other hand, the tinier ones get filtered out while passing through the inner regions. Most residents in Maine, New Hampshire, Oregon, or Wyoming, get water from deep-water wells. In these cases, the residents must use a sediment filter.
Even if you have feedwater from large water treatment plants, you should install a sediment filter before the tap.
If you’re looking for a water purifier with a strong sediment filter, you should check out Frizzlife SP99 water filter. Check out the product on Amazon.
The Second Stage: Activated Carbon Water Filter
What is an activated carbon water filter?
An activated carbon filter uses the exhilarated carbon granules to attract chlorine, lead, and organic compounds from the water. In addition to that, it restores the freshness into the water and gets rid of the bad taste.
More than 90% of the household water filters come with an activated carbon filter. In general, the Carbon water filters remain either as a pre-filter or a post-filter. You will also find water purifiers solely based on Carbon filtration.
The activated carbon filters can be of two types-
- Granular activated carbon water filter (GAC) and
- Carbon Block water filter
In GAC, the carbon particles remain in the form of granules. On the other hand, the particles get a cylindrical shape in Carbon block water filters.
How do activated carbon water filters work?
The activated carbon water filter attracts the Chlorine, Lead, Arsenic, and organic compounds with its surface. As a result, the impurities get absorbed at the exterior. The purified water becomes free from organic waste.
The higher the surface area, the better the purification. Blocks of Carbon get pulverized at high temperatures. As a result, the surface area increases. And, in this fashion, we get activated Carbon.
Like the sediment filters, carbon filters also have a plastic housing. In the case of GAC, there will be granules of Carbon inside. Meanwhile, in carbon block filters, there will be a cylindrical Carbon block inside the housing.
Generally, the water enters into the filter, and the impurities cling to the surface. As a result, a layer of organic compound gets created over time.
In general, carbon-based water filters can last for six to twelve months. After that, you will need to change the cartridges. If you’re looking for a timeline to replace filters or cartridges, check out our post here.
The Third Stage: Reverse Osmosis Membrane
What is a reverse osmosis membrane?
A reverse osmosis membrane is a partially permeable membrane that gets rid of the dissolved solids from the water. In addition to that, it also removes bacteria, viruses, and harmful chemicals from the water.
The feedwater we get every day comes with a variety of minerals dissolved inside. On one side, you will find Magnesium, Calcium. Similarly, you will also find unwanted ions like lead, arsenic, iron, and so on.
The semi-permeable RO membrane only allows the water molecules to go through. As a result, you get pure water at the output. Currently, the RO filters are the most widely used household water filters everywhere.
How do RO filters work?
The RO membrane uses the tap water pressure to filter the dissolved solids from the water. As the membrane only lets water molecules pass, the impurities get left behind.
After reverse osmosis, tap water gets divided into two types. We call the pure and clean output water the permeate water. The remaining stream of water holds all the dissolved solids. And, we call this the RO reject water.
The tap water pressure holds the key for RO water filters. When the pressure goes below the recommended level, the reverse osmosis membrane won’t work.
You can check out our post here to find out details about water pressure in RO filters. The RO membranes are especially helpful when your tap water has a high TDS value.
You can check out our post here to find out more about reverse osmosis water filters.
The Fourth Stage: Alkaline Water Filter
What is an alkaline water filter or ion exchanger?
An alkaline or an ion exchanger water filter is a filter that restores minerals into the water. Although it is known as a filter, it doesn’t behave like one. Generally, an alkaline water filter remains as a post-filter in the RO water purifier setting.
During reverse osmosis, all the dissolved solids like Calcium, Magnesium get washed off. As a result, the pH of water goes down. Also, the RO purified water lacks natural minerals.
That’s why we resort to an alkaline water filter. It adds an adequate amount of minerals to the water stream. Consequently, the water gets back its natural taste. The pH value increases as well.
If you would like to know more about the pH of water, check out our post here.
How does an alkaline water filter work?
The alkaline water filters work as a stock of lime and other salts. The pure water from reverse osmosis lacks electrolytes. As the water flows through the alkaline filter, the minerals start to mix with the water.
As a result, the water gets back its natural taste. Besides, an ion-exchange mechanism gets employed in some alkaline filters. In this case, the water would flow between two electrodes.
In the electrodes, the water will exchange ions like lead, iron, mercury, and others with Sodium, Magnesium, and Calcium. Consequently, the water becomes healthier.
If you would like to know more about alkaline water filters, you should visit our post here.
Also, if you’re looking for an alkaline water filter, you can check out the iSpring RCC7AK 6-Stage under sink water filter on Amazon. Check out our review of the product here.
The Fifth Stage: Ultraviolet Ray Disinfector
Ultraviolet ray disinfectors use UV rays to kill and neutralize germs and microorganisms. Due to nature, the UV disinfectors don’t qualify as water filters. But, many water filters feature it as an additional unit nowadays.
The UV disinfectors run on electricity from a battery source. Generally, the water treatment plants get rid of most of the germicides by adding Chlorine and Chloramine.
Then, the water travels to our home through the distribution network. On the way, viruses, bacteria, and other organisms can make their way into the water.
Although the reverse osmosis membrane can wipe out most of the germs, some still get through. That’s why UV disinfectors are so vital. The UV rays would either kill the germs or render those sterile.
As a result, the water becomes safe to drink. If you’re looking for a water filter with a UV disinfector attached, you should take a look at the Expresswater 11 Stage RO water filter. Check it out on Amazon.
What are the differences between 3-stage, 4-stage, 5-stage, or 6-stage water filters?
Water filters differ from each other based on the number of stages those provide. For instance, some water purifiers come with three or four levels, while others feature more.
The number of stages in a water filter means how many segments it has inside. For example, there might be a sediment filter, an activated carbon filter, and a RO membrane in a 3-stage water filter.
Repetitions can also occur here. For instance, a sediment filter and two activated carbon water filters can form a 3-stage water filter.
In general, most 3-stage water filters come with a sediment filter and two carbon filters. Here, one carbon filter is GAC type. The other one is an activated carbon block filter.
On the other hand, a 4-stage water filter generally has all three stages like before. Additionally, a reverse osmosis membrane will stay in between the carbon filters.
You will come across an additional alkaline filter inside a 5-stage water purifier. In six-stage water filters, there will be another carbon block filter just after the RO membrane.
Besides all these, a UV disinfector unit will be present in water filters having seven stages or more.
Here we have a list showing you the best water filters in the market. We have also included the total number, type of stages those have. Check it out here.
Highlights of the top water filters
| Name of the water filter | Sediment Filter | Pre Carbon Filter | RO Membrane | Post Carbon Filter | Alkaline Filter | UV Chamber | Total No of Stages |
|---|---|---|---|---|---|---|---|
| iSpring WGB21B | Yes | Yes | No | No | No | No | 2 |
| Frizzlife SK-99 | Yes | Yes | No | No | No | No | 3 |
| iSpring US31 | Yes | Yes | No | No | No | No | 3 |
| Whirlpool WHER25 | Yes | No | Yes | Yes | No | No | 3 |
| Aquasana AQ-5300 | Yes | Yes | No | No | No | No | 3 |
| Brodnell Coral UC300 | Yes | Yes | No | No | No | No | 3 |
| APEC ROES-50 | Yes | No | Yes | Yes | No | No | 5 |
| iSpring RCC7 | Yes | Yes | Yes | Yes | No | No | 5 |
| APEC ROES-PH75 | Yes | Yes | Yes | Yes | Yes | No | 6 |
| iSpring RCC7AK | Yes | No | Yes | Yes | Yes | No | 6 |
| Express Water ROUV10DCG | Yes | Yes | Yes | Yes | No | Yes | 6 |
| APEC ROES-PHUV75 | Yes | Yes | Yes | Yes | Yes | Yes | 7 |
| Express Water ROALK5D | Yes | Yes | Yes | Yes | Yes | No | 10 |
| Express Water ROALKUV10DCG | Yes | Yes | Yes | Yes | Yes | Yes | 11 |
How many stages are necessary for a water filter?
Any six-stage water filter covers all the required aspects of safe and pure drinking water. A reverse osmosis membrane along with a sediment filter, three activated carbon filters (two pre-filters, one post-filter), and an alkaline filter makes up the perfect tool to ensure pure and safe water. Moreover, an additional UV disinfector unit will further reinforce your safety.
A perfect example of six-stage water filters is the APEC ROES-75 RO water filter. You can also check out the Spring RCC7AK six-stage RO water filter. Click here to check out the reviews.
If you’re looking for a water filter with a UV disinfector, you should take a look at the Express water 11-stage RO water filter. Check out the product here on Amazon.
Final verdict
Throughout this post, we’ve discussed various stages a water filter can have. We’ve shown you how those levels work coherently to provide you safe drinking water.
Water filters are vital household products nowadays. Therefore, you need to have a clear idea of how the product works. If you would like to know more about the components of RO water filters, you should check out our post here.
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