Water filter cartridges

Water filter cartridges are the single most important element in any water filter system. Essentially, these devices are the ones removing dangerous contaminants from your water source, so it’s important to choose the right water filter cartridges for your system and ensure their timely replacement and maintenance.

Depending on the brand, model, and contaminants they’re designed to target, water filter cartridges can contain different types of filter media or a combination of several types of filter media in an effort to remove as many types of contaminants as possible.

In this article, we’ll discuss some of the best water filter cartridges you’ll find in a typical multi-stage water filter system, and what each filter is designed to do in such a set-up.

Best water filter cartridges in multi-stage water filter systems

You may be inclined to choose a water filter system based on its price or brand, but what you should pay closer attention to is the water filter cartridges your system contains. This is important because the type of filters and their micron rating (the size of the particles the filter is capable of removing) will determine the filtration efficiency of your water filter.

If you’re looking to buy a multi-stage water filter system (e.g. reverse osmosis filter), you’ll typically encounter the following set-up:

Sediment water filter cartridges

Sediments are small particulates like rust, sand grains, clay particles that either occur naturally in your water source or that water picks up as it travels through water pipes. These sediments may be small enough to not be visible to the naked eye, but even so, with time, these suspended solids may interfere with the performance of your kitchen appliances by clogging them, for example.

Usually, sediment filters are used in multi-stage water filters as a pre-filter either to protect a more expensive filter in the system (e.g. to protect the reverse osmosis membrane from clogging) or to enhance the efficiency of another filter (e.g. by removing sediments from water the efficiency of UV filters is increased).

By nature, sediment filters are complementary filter cartridges and they are rarely – if ever – used as stand-alone filters. In terms of filter media, they can be made of polypropylene, cellulose, ceramic, glass fibre, polyester, cotton, and wound string/cord. Some sediment filters are washable (e.g. pleated polypropylene sediment filter), which extends their service life.

Sometimes, sediment filters are used as post-filters in water treatment systems that create sediments. One example would be scale control systems that create scale crystals, which need to be removed from the water.

In terms of micron rating, water filter systems with 6 or more filtration stages usually start out with a 5-micron sediment filter and then they contain another sediment filter with a lower micron rating (e.g. 1-micron) to remove fine sediments.

The best sediment filters are those that remove sediments with the least amount of flow restriction and have a long service life. Pleated sediment filters are known to excel at both categories.

Here at WaterFilterShop.co.uk, we offer a wide range of sediment filters from reputable water filter manufacturers like Watts, Spectrum, Pentek, etc.

Activated carbon water filter cartridges

Carbon is probably the most ubiquitous filter media in the water filter industry thanks to its high surface area and contaminant adsorption capacity. Unlike sediment filters, carbon filters can be used to remove chlorine, volatile organic compounds, THMs, pesticides, herbicides, and some types of microorganisms.

Carbon is ground into small particulate sizes either to create carbon block filters or granular activated carbon (GAC) filters. Carbon blocks contain solid blocks of compressed carbon, while granular activated carbon filters contain loose granules of carbon.

Each type of carbon filter has its advantages and disadvantages. Thanks to its larger surface area, carbon block filters perform better in terms of contaminant removal since water takes longer to pass through the filter. Flow rates, however, are slower. A GAC filter on the other hand ensures better flow rates, but don’t remove as many contaminants as carbon block filter do. GAC is also used in shower filters precisely because of the good flow rates it provides.

Usually, you’ll find both types of carbon filters in multi-stage systems, but while carbon block filters are used as a pre-filter, GAC are most commonly used as post-filters or polishing filters to further remove any remaining chemicals and improve the taste of water.

When these activated carbon filters become saturated with contaminants it’s imperative that you replace them, because they become a breeding ground for bacteria. Some types of carbon filters are impregnated with silver, which confers them bacteriostatic properties, but even so, they shouldn’t be used beyond the end of their service life.

Just like sediment filters don’t remove chemicals, carbon filters have their shortcomings too. Thus, they don’t remove fluoride, heavy metals, mineral salts, and certain microorganisms. This is why, when used on their own, carbon block filters are usually used for water taste and odour improvement, but most commonly these filters are paired with other filters to offer a more thorough filtration.

Reverse osmosis membrane

The reverse osmosis membrane is at the heart of every reverse osmosis system. This semi-permeable membrane can tackle a wide spectrum of contaminants like dissolved salts, mercury, lead, asbestos, cysts, etc. as household water pressure pushes tap water through the membrane.

The RO membrane can be made of thin film composite (TFC) or cellulose tri-acetate (CTA), with the former being more common in today’s reverse osmosis systems. Reverse osmosis membranes are prone to clogging and have little resistance to chemical disinfectants like chlorine (while CTA membranes have better chlorine resistance than TFC membranes, they can’t handle water with a pH over 8.5). Therefore, it’s important to equip a reverse osmosis system with the appropriate pre-filter cartridges.

Reverse osmosis membranes have a longer service life than most filter cartridges on the market, some models lasting even up to 3 years. This is because they are built for resistance and they are protected by pre-filters.

Best water filter cartridges for single-stage water filter systems

While multi-stage water filters are known to offer a more in-depth filtration, the filtration capabilities of some single stage filter systems can be on par with the filtration capability of complex filters.

Although single-stage systems may use only one filter cartridge, generally, these filter cartridges are not your run-of-the-mill filter cartridges since they use a combination of filter media contained within one filter. This can be a blend of ceramic filters coupled with ryolite, KDF or silver impregnated activated carbon.

Probably the most representative examples of these type of complex filter cartridges is the ones manufactured by Doulton. The Doulton Ultracarb candle, for example, is a combination of ceramic and carbon-block technology, which is designed to provide a sub-micron level filtration. The silver locked within the ceramic structure confers bacteriostatic properties to the water filter candle, thus, preventing bacterial grow-through.

As a result of this ingenious filter media combination, the Doulton Ultracarb removes and reduces the following contaminants: 99% of soluble lead, iron, hydrogen sulphites, pathogenic bacteria, asbestos fibres, chlorine taste and odour, VOCs, etc.

Water filter cartridge maintenance

Even the best water filter cartridges have an “expiration date”, which, depending on the quality of your water source, may come sooner than the recommended replacement date. Therefore, you should replace your filters as soon as they reach the end of their service life, or when you notice changes in the taste, odour or appearance of your tap water if these come sooner.

Some filters (e.g. ceramic filters, pleated filers) can be reused by washing them, however, they can’t be reused indefinitely. We recommend washing and reusing these filters only when you don’t have replacement parts at hand and you need to extend the service life of your filters for just a few days until you can get replacement filters.

When washing these filter cartridges, make sure not to drop them, since you may cause fissures that will let contaminants pass through and get into your water. Ceramic filters are known to break quite easily, so take every precautionary measure to avoid dropping them. If you do drop them, avoid reusing them.


As you’ve probably concluded from this article there is no single best water filter cartridge for your residential water filter system. Each filter is designed to carry out a well-defined task, which the other filter may not be able to achieve. Therefore, the more types of filter media a system contains, the better.

Ultimately, the best filter cartridges for you are the ones that will remove the contaminants present in your tap water. In some cases, and with some water sources, it may take a single filter cartridge to achieve the desired filtration level. In other cases, it may take six filter cartridges or more to achieve the desired filtered water quality.

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Puricom CS Sediment Filter


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