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How Do Home Water Filters Work?

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The need for home water filters is seen by some as a waste of time because their local water authority has deemed that tap water is safe to drink. On the other side of the debate are those who are aware that unseen elements exist in the water that may be deleterious to their health. If you've ever experienced bad tasting water, water the smells (chlorine) or is cloudy and has other visible matter present, you probably now own a water filter. If you don't own a water filter and have ever wondered “how do water filters work” read on.

How Do Water Filters Work?

Most water filter systems work in essentially the same way. Water passes through a removable cartridge filled with a filtering medium such as activated charcoal.

Water treatment plants use two types of filtration: physical and chemical. Physical filtration involves pushing the water through a fine mesh to catch any larger particles while chemical filtration uses activated carbon to absorb contaminants like chemicals and organic matter.

These techniques are also present in our home water filters just on a smaller scale to catch anything the treatments may have missed and to filter out any harmful additives added to the water during this process.

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Types of Home Water Filters Available:

If you want a filter at home, you have two several options:

  • Water pitcher filter
  • On-tap filter
  • Countertop filter
  • Undersink water filter
  • Reverse Osmosis
Doulton Undersink Water Filter with Sediment Filter
Doulton Undersink Water Filter with Sediment Filter

Undersink and Countertop Water Filters

We had a look at Brita vs Berkey water filters in an earlier post. Berkey is a great example of a counter-top water filter. These and undersink filters do a much better job of removing impurities from your town water than a water jug or on-tap filter will ever do.

If you are serious about drinking clean water (and why wouldn't you be?) a countertop or undersink water filter is the way to go in our opinion. The contaminants these filters are able to remove is far superior to a water filter or on-tap unit. Many of these filters struggle to remove chlorine which is probably the easiest chemical to remove! Fill your kettle with filtered water and enjoy a seriously good cup of tea (or coffee)

Water Jugs & On-Tap Filters

For the pitcher all you do is fill it with water, place in your fridge and the spout, which is fitted with the filter, will treat your water as you pour each glass. With an on-tap filter, it is fitted to your existing tap and the water is filtered right as it comes out of the tap, some even come with a special shower filter so you can wash vegetables with some clean water. The water pitcher options are the most commonly used because they are more affordable and can simply be popped in the fridge with no installation required. 

These filters may appear very different, but they are, in fact, the same when it comes to how the water is filtered. The key to both of these designs is activated carbon. The carbon is cylindrical that gives it a large exterior surface area, so the water is passed through the outer layer and pours out through the centre leaving all the unwanted stuff behind. But why activated carbon you might ask? This special substance, when activated, becomes very porous and is therefore able to absorb contaminants like chlorine, pesticides, and other organic matter. The filter is essentially a collection of spherical particles that act like a magnet that attracts all these different substances including metals like lead, mercury or copper and traps them within it.

Some Of The Contaminants Removed By A Good Water Filter

  • Chlorine
  • Heavy Metals
  • Bacteria
  • Volatile Organic Compounds such as pesticides and herbicides
  • Rust particles (from aging pipe infrastructure)
  • Microplastics
One Of The Biggest Nasties You'll Come Across: Cryptosporidium Parvam

Activated Carbon, Ion Exchange & Reverse Osmosis

The only thing that carbon doesn’t attract and eliminate are nitrates and bacteria as they don’t bind with it but treatment at the water plant should handle these issues. The most common material that these carbon filters are made from is coconut shells because it is the most efficient and eco friendly, but they can also be made from coal, wood or other high carbon nut shells. They can catch any substances that are 2 microns in size or larger so it can catch microplastics and even some bacteria.  

Some filters also use an ion exchange system, which uses resin to reduce the water’s hardness as well as filtering out calcium and magnesium, but they are not as common. Another less common method is reverse osmosis that pushes the water through a semipermeable membrane that can even prevent dissolved solids from passing through. This is very effective and removes most contaminants, but it also removes the healthy minerals naturally present in water, which is a large downside as water is such an easy way to get some iron, potassium, sodium and zinc into your diet among others.  A decent reverse osmosis system will have the option of adding a mineral filter which will return small amounts of healthy minerals to you water.

Why Use A Water Filter? 

Your tap water may look pure but will certainly contain invisible contaminants that may not be doing you any favours health-wise. These particles could be anything from microplastics that are present in 90% of our tap water, metals present due to old or corroded pipes, various organic matter and harmful chemical additives from the town water treatment process.  

What a filter will also help with in most cases is making the flavour better in areas that have higher levels of chlorine or minerals which affects what the water tastes like and sometimes make it cloudy. Filtering your tap water means that you can drink the water supplied to your home instead of buying bottled water, which in turn will save you money as well as being more environmentally friendly as it will help you reduce your plastic waste. 


How Do Water Filters Work: Summing Up

A water filter is basically the last line of defense for those that are concerned about their water quality to give them peace of mind. If you think about it there’s no way of us really knowing 100% what's in our water, and using a filter can combat all these unknowns.

Amy Hand
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