How Do Water Filters Work?

What are Water Filters?

Water Filters remove unwanted impurities from water such as sediment, taste and odor, hardness, and bacteria to result in better quality water. From producing better-tasting drinking water to more specialist applications such as brewing coffee and making crystal clear ice, we offer a huge range of filters and cartridges to solve any number of water-related issues.

The 5 Types of Filters

Subject to your application, i.e. what you’re trying to remove or in some circumstances trying to stop, there are 5 types of water filters:

1. Mechanical Filters
2. Absorption Filters
3. Sequestration Filters
4. Ion Exchange Filters
5. Reverse Osmosis Filters

Each one of these addresses a different water problem and many filters actually use a combination of these methods to perform multiple levels of filtration.

How Do They Work?

Water is one of the most important substances on the planet, it covers 71% of the Earth’s surface and the human body can contain as much as 75% of the stuff. Water is vital to a huge number of applications including agriculture, science, medical, transportation, heating, recreation, and food processing as well as washing, and perhaps most important of all: drinking.

For the majority of us, drinking water comes from a treated municipal supply that is safe to drink but will often feature unpleasant tastes and odors from chemicals such as chlorine which are used to disinfect the water and keep it free of germs and bacteria. Depending on where you live, you may also find that your mains water causes limescale deposits to form which can block pipes and damage appliances. These issues, chlorine taste/odor, and limescale formation are just two among a host of other common water problems which can be solved by water filtration. But how do water filters actually work?

Mechanical

The basic idea of mechanical filtration is to physically remove sediment, dirt or any particles in the water using a barrier. Mechanical filters can be anything from a basic mesh that filters out large debris to a ceramic filter that has an extremely complex pore structure for ultra-fine filtration of pathogenic organisms.

A filter that utilizes mechanical filtration will usually be given a micron rating which indicates how effective the filters are in terms of the size of the particles it is capable of removing. Common ratings you might see include:

• 5 micron – Will remove most particles visible to the naked eye.
• 1 micron – Will remove particles that are too small to see without a microscope.
• 0.5 micron – Will remove cysts (giardia and cryptosporidium).

 

Absorption

Absorption in water filters is most commonly carried out by carbon, which is highly effective at capturing water-borne contaminants. The reason carbon absorbs contaminants so readily is that it has a huge internal surface that is jam-packed with nooks and crannies that can trap chemical impurities such as chlorine.

Most common domestic filters contain granular activated carbon (GAC) which reduces unwanted tastes and odors by absorption. More expensive filters use carbon block elements which are generally more effective and usually carry a micron rating for particle removal.

A variety of different substances can be used to make carbon for filters including wood and coconut shell, with coconut shell filters being more effective but also more expensive.

 

Sequestration

Sequestration is the action of chemically isolating a substance. Food grade polyphosphate is commonly used in scale inhibiting filters to sequester the calcium and magnesium minerals that cause limescale and corrosion. However, polyphosphate is generally only introduced in very small amounts and it only inhibits scale rather than eradicating it. This means that polyphosphate does not soften the water but instead works to keep the minerals within the solution, preventing them from forming as scale on any surfaces they come into contact with.

Due to the hard minerals still being present in the water, scale inhibition isn’t suitable for all applications. Instead, water softening using a process such as an ion exchange is usually recommended in water areas with alkalinity levels of 180ppm or more (very hard water) and applications where water is kept at a constant temperature of 95°C or more.

 

Ion Exchange

Ion exchange is a process used to soften hard water by exchanging the magnesium and calcium ions found in hard water with other ions such as sodium or hydrogen ions. Unlike scale inhibition, ion exchange physically removes the hard minerals, reducing limescale and making the water suitable for applications where it is kept at a constant high temperature e.g. in commercial coffee machines.

Ion exchange is most commonly carried out using an ion exchange resin which normally comes in the form of small beads. A similar type of resin is used in some Water Softeners and in the case of a water softener the resin utilizes sodium ions which need to be periodically recharged to prevent the resin from becoming ineffective. As water filters are usually sealed units you would simply replace the filter with a new one though it should be noted that
Calcium Treatment Units (CTUs) can be returned to the supplier and regenerated.

Resins that utilize sodium ions aren’t usually used in drinking water filters as the amount of salt (sodium) that can be present in drinking water is legally limited to 200 milligrams/liter. As sodium ion exchange increases salt levels, a hydrogen-based ion exchange resin is the preferred option for filters.

Reverse Osmosis

Reverse osmosis (RO) is the process of removing dissolved inorganic solids (such as magnesium and calcium ions) from water by forcing it through a semipermeable membrane under pressure so that the water passes through but most of the contaminants are left behind.

Reverse osmosis is a highly effective way of purifying water and is usually combined with a number of other filters such as a mechanical (sediment) filter and an absorption (activated carbon) filter in order to return water with few contaminants remaining.

Reverse osmosis systems use water pressure to force water through the membrane so it uses no electricity, though a certain amount of wastewater is produced that has to be sent to the drain. The extra filters involved in multi-stage water filtration can make a reverse osmosis unit more expensive than other filtration methods but in applications where 99.9% pure water is required, RO offers the finest level of filtration available as is increasingly being used to treat water made for Coffee

Combinations

Each filtration method has limitations on what it can remove, so most water filters or filtration systems use a combination of methods to achieve a specific level of water purity. To give an example, household water jug filters will generally use mechanical, absorption, and ion-exchange whereas inline filters will utilize mechanically and absorption with the possible inclusion of sequestration if the filter is designed to inhibit scale. Reverse osmosis systems can utilize mechanically, absorption, and of course, reverse osmosis depending on how many stages the RO system has.

By understanding the five different methods by which water can be filtered and the way they can be combined, you should hopefully find it easier to establish which kind of filters you need for any given application.

Water Filter Systems

Water Filter systems remove unwanted tastes and odors from mains water to provide clean, fresh-tasting water straight from your tap. Domestic systems such as a Watergem are compact and easy to install under a sink or small space. Commercial water filter systems are slightly different depending on the use in the kitchen or on the specialty equipment. Water filter systems come fully equipped with the kit to get you set up and tapped into the existing water line.

Coffee Machine Water Filters

Water is imperative in making the perfect coffee. Normal filtration rules don’t apply to the coffee bean which needs a very special blend of minerals before it will release its full flavor. This, complete with protecting and cleaning expensive espresso machinery means coffee machine filters are another level, luckily we are well equipped to handle coffee machine water filters

Inline Water Filters

Inline filters sit directly on the water line or appliance and the water passes through the filter before reaching the tap or appliance. Commonly used in households this type of filtration is perfect for under-sink installations due to its small size.

Inline filters can reduce common problems with municipal water such as chlorine taste, odor, and bacteria’s providing bottled water tasting water without the plastic waste. The Hydro + range of inline water filters is one of Europe’s top-selling filters.

Drop-In Filters

Drop-in filters are made to fit inside of a water filter housing. Housings vary depending on the use but the most common sizes are 10″ and 20″. We also stock Jumbo housings and the Watts Big Bubba housing

Fridge Filters

Fridge filters are required to filter the feed water coming through to the drinking water and ice mechanism. Most commonly found on American-style fridge freezers, the size and compatibility of the filter vary depending on the make/model and style of the fridge freezer.

Water Filters for Commercial Foodservice

Combi ovens rely on good quality water for their steam. The chemical reaction of poor-quality water being heated to produce steam or hot water is a main contributing factor of causing limescale which can lead to breakdowns. Everpure Claris is one of the most trusted brands and supplies catering equipment manufacturers and their service partners tailored combi oven filters