The NatureDoc guide to water filters

Are you one of the growing number of people concerned about pollutants in your drinking water? Do you hate the dull taste of your tap water? Or are you on a mission to reduce single-use plastic from bought water? There are lots of reasons to filter your water at home these days, and if you are keen to buy a water filter, but need help deciding which one to choose, then read on.

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How safe is British tap water?

The Drinking Water Inspectorate (DWI) in the UK actively monitors our water supply and has amongst the world’s strictest regulations, thus making British tap water one of the cleanest and safest supplies out there. The water from your taps at home has been through rigorous filtration and testing processes and 99.97% of tap water tested by the DWI complies with their high standards. Their tests include physical, chemical, and microbiological analysis. You can easily check which contaminants your local water company tests for on their website, as well as information about what they add to your water. You can find out here if you’re unsure which water board you currently have.

However despite this, many people are concerned about contamination from the atmosphere, industry, agriculture and pharmaceuticals, and they worry that residues from these may be lurking in the water system. The concern is that these may be toxic, carcinogenic, hormone disruptors, or pharmaceutically active compounds, and that the current filtration methods at water treatment plants are not appropriately removing them. The DWI has suggested that they cannot be sure of the potential impacts of ‘forever chemicals’ in drinking water, such as perfluorinated substances (PFAS)  and microplastics.

What is in our tap water?

Your tap water may look clear, but it is full of microscopic beneficial particles of minerals and it may also contain trace amounts of some unwanted nasties.

Natural minerals
These minerals are what you want and need in your tap water! The beneficial minerals in tap water typically include calcium, magnesium, sodium, copper, and trace amounts of potassium, phosphorus, iron, selenium, zinc, and chromium. The levels of minerals in our tap water depend on the source of the water and the filtration methods at the water treatment plant. Tap water with a high level of cacium is known as “hard” water (which leads to limescale). These minerals are vital to the healthy function of all of our body systems and add the taste we attribute to clean water. Although food is usually the primary source of these minerals, we also need to consume minerals through the water we drink.

It is a regulatory requirement for water companies to disinfect their water with chlorine to remove harmful bacteria and viruses. Chlorine is highly volatile and most of it disperses shortly after coming out of the kitchen tap. However, chlorine in tap water is a common concern, and home filters often remove it. The chlorine levels in UK tap water are well within the drinking water guidelines from the World Health Organisation whose limit is 5mg/l, with most water companies in the UK keeping it below 0.5mg/l.

To remove chlorine’s distinctive smell and taste, keep a jug of tap water on your kitchen work surface, where the chlorine will disperse over time. However, once the chlorine has dispersed, bacteria will start to grow more easily, so it is important to remember to refresh the water every day – this includes in-jug and countertop water filters as well as coffee machines.

Many re-usable water bottles harbour unthinkable germs, so it may be a good idea to refill them from chlorinated water!

Fluoride is added to the water supply by a very few water boards to help prevent tooth decay. However, most do not need to do this and trace fluoride occurs naturally in the water. The only places in the UK that currently add fluoride added to the water are: United Utilities, Northumbrian Water, Anglian Water, Severn Trent Water and South Staffordshire Water. And you can check the fluoride levels of the water in your area here.

Just like too much water can kill you (really!), as you can imagine, there are problems with too much fluoride and some studies have linked excessive fluoride to tooth enamel damage, neurological problems and hormonal dysregulation.

Heavy metals
Even though most water authorities monitor tap water for heavy metals such as lead, arsenic and mercury, these can sometimes creep into the water system inadvertently. If you get your water from a private supply, then heavy metal contamination needs to be tested regularly. Also check if you still have lead or lead soldered copper water pipes (illegal to install in the UK since 1999) or even a lead-lined water tank. If so, then these need replacing.

The presence of microplastics in our drinking water is a relatively new area of research. Techniques to measure their occurrence and removal during treatment is still being debated, as well as the potential health risks associated with their intake via our drinking water. 

Companies who make at-home water filters are increasingly suggesting that their membrane filters can block microplastic, but this research is still emerging. In any case, a good way of avoiding these microplastics is to switch from plastic water bottles to stainless steel or glass water bottles.

Pharmaceuticals & hormones
This is where things get a little bit more complicated. There are estimated to be over 130,000 pharmaceutical chemicals in circulation (including personal care products, medicines and hormones) that may end up in our water system. Many of these chemicals go unmonitored which makes it a challenge to assess any potential health risks from exposure to trace amounts in our tap water.

The effects of these chemicals have been linked to issues with the immune system, metabolic disease, endocrine disruption, reproductive problems, diabetes and cancers. It is very worrying, although the DWI’s studies have concluded that the “non or very low detectable levels of pharmaceuticals in drinking water do not pose an appreciable risk to human health”. The long-term health effects of these chemicals are unknown, and it is suggested that we try to avoid them as much as possible.

PFAS “forever chemicals”
Per- and polyfluoroalkyl substances (PFAS) are known as ‘forever chemicals’ because they are virtually indestructible and cannot be broken down either by nature or by our bodies. They mostly come from industrial processes like the metal industry and are also found in fire retardants and stain-resistant coatings on textiles, and find their way into our water system.

They are linked to a range of health issues including testicular cancer, thyroid conditions and infertility as well as inflammatory conditions and allergies. PFAS can be filtered out by carbon filters which can remove over 90% of them and Reverse Osmosis systems which can remove about 99% of them (see below for how these work).

However, UK water companies are currently not required by law to reduce them until they are at a level that is considered ‘high risk’. In fact, our water companies are only required to measure levels of 47 types of PFAS where there are actually thousands of different types.

The Royal Society of Chemistry has developed a map where you can check the levels of PFAS in your area here.

What are the ways of filtering tap water?  

Home water filter systems are typically through a filtering substance, reverse osmosis, UV disinfection, or a mixture of the above types  Each method can filter different types of contaminants to different levels, often removing them completely.

Filtration media substance
Granulated activated carbon is the most common home filtration media. The activated carbon is created from charcoal from a variety of sources (including options that are marketed as greener such as coconut or rice husks). The carbon filter has many microscopic pores that trap impurities including organic contaminants and some heavy metals. The activated carbon can be impregnated with added crystallites (an ion exchange system), which enhances its ability to remove impurities; and high-quality filters can remove the particles that are harder to get rid of, such as fluoride and hormones.

  • Positives: An effective way of filtering out contaminants including fluoride and hormones.
  • Negatives: Slow to filter and only suitable for small volumes of water.

Reverse osmosis
This is a technology which uses membranes, through which the water is pushed at pressure. The process is so efficient that it removes nearly everything in the water, including beneficial natural minerals. Most reverse osmosis systems add some of those minerals back afterwards, but you’ll still end up with less than in natural water.

Reverse osmosis is quite wasteful of water because it rejects a large amount of waste water in the process. This means that several litres of water are used for every litre of filtered water that is produced (something to watch out for if you are on a water meter). They are usually more expensive and complex than simple filter systems.

We live in a very hard water area so we have a water softener for the house, which has been amazing, but you shouldn’t drink softened water routinely as the process adds a lot of sodium. So a few years ago after my husband did a lot of research, he got a plumber to install a big expensive reverse osmosis filter for the kitchen to take the sodium and other potential nasties out of the tap water and then add some minerals back in with multiple types of filter (6) and a remineralisation cartridge. After a month or two, no one could stand it any more as it tasted horrible, and my husband ripped it out. After doing so and paying the same plumber to install a new mains unsoftened water pipe through the house to the kitchen, he noticed that the reverse osmosis membrane was still in its box, and not in the filter housing. It had never been installed properly! So do find a plumber who has experience in reverse osmosis installation!

  • Positives: Provides contaminant-free water and there are whole-house systems available to filter both drinking water and shower/bath water.
  • Negatives: Filters out all minerals, and even if you remineralise your water, it won’t have as many vital minerals as fresh or mineral water.

UV disinfection
UV is not a filter as such, but kills bacteria and other pathogens through UV light. Because it adds no chemicals, it does not create disinfectant-resistant bacteria or other harmful chemicals. But it is rarely suitable on its own as a home filter since it has no way of removing things like lead, chlorine or other chemicals.

  • Positives: Very effective against bacteria, cheap and fast.
  • Negatives: Not effective against mineral or chemical contaminants.

Which water filter to buy?

There is such a huge range of choices when it comes to picking your home water filter, it can all be quite overwhelming. Your choice of filter will not only be based on what potential contaminants it can remove but also on cost, ease of installation and maintenance, and convenience to use.

Remember that this is an unregulated industry and there is often little to no independent research to back up the claims made by individual companies. There can also be an issue with knowing exactly how long a particular filter maintains the stated level of removal of contaminants – not only in the number of months but also in the quantity of water passing through the filter and the levels of pollutants in the original tap water.

I asked the team at NatureDoc for their favourite water filters – and I’ve included our top picks. But as everyone’s needs are different and prices change, you may want to go and check out others for yourself. We have not received anything or expect to earn anything from the vendors or manufacturers below. None of the links are have any benefit for us. This is from our team’s own experience of filters we have bought and used ourselves.

Jug water filters

Jug water filters are the choice with the lowest cost entry point. The tap water is poured into the top reservoir, and it moves through the filter (usually a couple of stages of filtration with two or more different materials). The filters are enclosed in a plastic (yup!) cartridge which needs to be replaced every few months. Jug filters are designed to improve water taste and can remove residual chlorine and dissolved organics, and some models are marketed as being able to remove a variety of other contaminants such as pesticides and heavy metals.

The manufacturers are quite bossy about renewing the disposable filter cartriges. Certainly their effectiveness will deteriorate over time, and they can end up being a breeding ground for bacteria.

Companies are now offering refillable cartridges in an effort to reduce plastic (Phox), apps to tell you when to change your filter (Brita), and more expensive models even have UV technology (Larq).

  • Positives: The cheapest option, with flexibility on the level of filtration.
  • Negatives: Not as effective at removing contaminates as the larger systems. Must replace the filters quite regularly. Kitchen clutter.

NatureDoc top picks:

  • Low budget: Brita range with Maxtra Pro – Reduces chlorine, some herbicides, pesticides and pharmaceuticals; and reduces levels of lead and copper. Filters last 4 weeks.
  • High budget: Larq Pure Vis – Produces water with a delicious and crisp taste. Reduces chlorine, lead, mercury, PFAS and haloacetic acids. The UV technology cleans the filter reducing buildup of bacteria. The filter lasts 2 months.

Countertop filters

Countertop filters can be enormous, holding up to 12 litres (which look a bit like a village hall tea urn!), or smaller versions that could be confused with a small coffee machine. They have a top reservoir where the tap water in poured into (although some can be plumbed in). The water then makes its way through a complex system of filters – usually a number of different types of activated charcoal and an ion exchange process.

It can take a few minutes for the water to pass through all these filters which ensures a greater removal of contaminates. These filters can remove bacteria, pharmaceuticals, pesticides, chlorine, PFOS and hormones.  Some brands allow you to choose to add extra filters (for example a supplementary fluoride filter) such as Doulton Berkefeld.

Other countertop filters use the reverse osmosis process with a remineralisation cylinder, such as Osmio, and even allow you to choose the temperature of your filtered water at the press of a button such as Skuma.

The filters need to be maintained and replaced. But some companies such as Berkey recommend replacing them as little as every ten years.

Elaborate countertop filters are my least recommended because they are neither cheap, like the jugs, or tidy, like fridge or under-counter filters.

  • Positives: Very efficient at removing contaminants.
  • Negatives: Can take a long time for the water to pass through the system. Takes up lots of space on the kitchen countertop and can be hard to clean.

NatureDoc top pick:

  • Doulton British Berkefeld Stainless Steel Gravity System – Comes in three sizes (6litres, 8.5litres and 12litres). Filters reduce chlorine, lead and other heavy metals, herbicides and pesticides and traces of pharmaceuticals. You can purchase add-on cartridges for fluoride removal. Filters last 6 months.

Refrigerator water filters

If your fridge has a water and ice dispenser, then the water will have passed through an internal filter. These filters are most often a form of granulated activated carbon filter and will need to be replaced to maintain effectiveness. Some companies offer different levels of filtration, so always check with them which contaminants their filters focus in on.

  • Positives: Hidden away in the existing kitchen appliance, so doesn’t take up any extra space.
  • Negatives: May forget to change the filter. Little choice on the effectiveness of the filters.

Sorry, we don’t have any recommendations here. These filters tend to be more of an afterthought on fridges and not marketed so strongly on specific filtration benefits.

Under-sink systems

These systems typically sit in the cupboard under your kitchen sink. They can be plumbed to your cold water tap or include a small separate drinking water tap that is fitted next to the main tap.

There is a huge array of choices for this type of filter. Some are highly complex systems that require a professional plumber, whereas other brands like Water2 are keen to show that even the most inexperienced DIY-er can install their system.

As there is more space under the counter, you can often fit bigger faster multi-stage systems and others are reverse osmosis systems such as Osmio. 

  • Positives: Hidden system that has a huge range of filtering options, so you can choose to filter what you want.
  • Negatives: Takes up cupboard space. May require plumbing-in by a professional.

NatureDoc top picks:

FreshWater Filter – Filters out bacteria, parasites, cysts, chlorine, trihalomethanes, pesticides, herbicides, oestrogens and heavy metals such as cadmium, lead and mercury. Filters should be changed every 6-12 months. This is the updated version of the filter I have used for over 20 years in three different homes.

Aquafilter 7 Stage Reverse Osmosis System with Mineralizing – This is the system we researched, bought, installed and, through no fault of the manufacturer, never got working. If we were going to use a reverse osmosis system again, this is where we’d start.

Round up

Even though British tap water is considered one of the cleanest in the world, a water filter can give you peace of mind to reduce any residual contamination even further, and ensure crisp clean-tasting water for you and your family.

There is no one “perfect” water filter option for everyone, as ultimately it is a matter of personal choice and priorities, but I hope this guide has helped you to make a more informed decision about which choice is right for you and your family.



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  1. So interesting – I just recently saw that there are plans to add more fluoride to deal with the NHS dentist crisis…and I bought a Water2 last week will see how we go with it