What is the best type of water filter? Distiller vs. reverse osmosis vs. gravity-fed
- Josie Shillabeer
- Aug 30
- 11 min read
Read our guide on how to choose the best water filter. Learn how they work, their benefits, and limitations.
At The Health Puzzle, we stress the importance of water and good hydration as one essential for optimal health, but as more people question the quality of what’s coming out of UK taps, should we be filtering our water and if so what’s the best way to do it?
In our last post we discussed why you should filter your water—yes, even in the UK! You can read this post HERE. In this post we are going to look at the different ways to filter your water and which one is the best.
This blog post answers the questions:
What are the different types of water filters?
How does each water filter work?
What are the benefits of each type of water filter?
What are the limitations of each type of water filter?
Who is each type of water filter best suited to?
Our top recommendations for each type of water filter
What is the best type of water filter?
There are three main types of water filtration: distillation, reverse osmosis and gravity-fed. While these options can filter tap water to make it healthier to drink, some do a much better job than others.
1) Distiller
What is a water distiller?
A water distiller is a device that filters water through the process of distillation. Distillation is ‘the action of purifying a liquid by a process of heating and cooling it‘. The best real-world example of this process is rain. As the sun heats water on the earth's surface, it turns the water to steam and evaporates. The evaporated water rises until it meets cool air and forms clouds made up of water droplets. Once the clouds become heavy, the water falls as rain.
Purifying water using distillation dates back to the Egyptian times, expect today, thanks to modern technology, there are now easy-to-use countertop systems. While designs vary, a water distiller typically comprises a large boiling chamber, a cooling system and a water collection container, such as a glass jug.
How does a water distiller work?
Tap water is added to the large internal boiling chamber.
The tap water is heated using electricity to create steam.
Contaminants, including PFAS (forever chemicals), organic and inorganic chemicals, toxins, heavy metals and other pollutants, are left within the boiling chamber trapped within limescale.
The best distillers have a small hole drilled in the condenser's top tube to help chlorine gas and many VOCs to escape. The best distillers have also been calibrated to heat water for the optimal balance between filtration speed, time for off-gassing and energy consumption.
VOCs with a boiling point above 100℃ will be left behind in the boiling chamber.
VOCs with a boiling point below 100℃ will either off-gas or be caught by the activated carbon filter.
Once the steam enters the cooling chamber found at the top of the device, it turns back into a liquid.
In the best distillers this water then runs through an activated carbon filter before entering the water collection container. This final stage of filtration acts as a backup, helping to remove any contaminants that may not have been removed through the distillation process.
Before refilling the boiling chamber with more tap water, users should give the chamber a quick rinse to remove the unwanted contaminants. Then, either monthly or bimonthly, depending on whether you live in a hard or soft water area, users should give the boiling chamber a thorough clean to help maintain the distiller.
What are the benefits of a water distiller?
After testing and reviewing many water filters, it has become quite clear that the benefits and limitations of water distillers far outweigh other forms of water purification. Here are some reasons you should opt for a water distiller as your water filter of choice:
Very pure water: Water distillers are known for producing the purest drinking water of all water filtration devices.
Very low risk of leaching: virtually zero risk of leaching contaminants, unlike other forms of water filtration. This is because water distillers do not require water to be forced through filters that may reduce
Easy to clean: The whole device is easy to clean, and you can utilise natural cleaning chemicals, such as white vinegar and citric acid.
Easy to repair: Many companies provide all the parts needed to rebuild or repair your water distiller.
Cheap, natural and easy to replace filter: The activated charcoal filters are low cost, made of natural materials, easy to replace and can be composted.
Low wastewater: While some water is lost through steam, the device does not produce large amounts of water waste through the filtration or cleaning process.
Sustainability: less wastewater, easy to repair, no plastic filters and compostable filters.
Low running cost: As a distiller has very cheap filters, the largest cost of running a distiller is energy usage. If you have solar panels, this can help to reduce running costs considerably.
What are the limitations of a water distiller?
Long filtration time: Devices can take up to four hours to filter four litres of water. This is much more time consuming than other filtration methods.
Noise: With the fan running continuously for up to four hours, this can provide unwanted noise pollution within your home. A way around this is to put the device on before you go to bed, so that you are not affected by the noise and wake up to lovely purified water.
Heat: As a water distiller works by heating water, the device gets very warm. This can increase the room temperature. While this is unwanted in summer, it can provide extra warmth in the colder months.
Strong smell: After using the device for several distillation cycles, the boiling chamber can develop a strong smell because of the buildup of contaminants. However, you can only smell this when the device is open during refilling and cleaning.
Heavy containers: You need to lift and manoeuvre 4L of water, something that may be difficult for some people.
Who is a distiller best suited for?
A water distiller is best suited for those who are looking for the purest drinking water available. It is easy to clean, repair and produces very low waste, making it a more sustainable option than other filtration devices. The water distiller is not suitable for those who have high electricity bills, but is a fantastic option for those with solar panels or who are looking to avoid expensive replacement water filters.
Our top-recommended water distiller
The best water distiller available in the UK is the H2O Labs Stainless Steel 300SSE model with glass carafe. It has all the features you need, and water doesn’t come into contact with plastic at any point during the purification process. Plus, H2O Labs sells unique carbon filter pods that are easy to use and last longer than others on the market.
2) Reverse osmosis water filters
What is reverse osmosis?
A reverse osmosis water filter is a device that uses multiple replaceable filters, including a reverse osmosis filter that contains a specialised semipermeable membrane that lets water through but larger contaminants cannot. Devices come in two key forms: countertop systems and under-sink units.
How does reverse osmosis work?
Countertop units:
Tap water is added to the water tank. Some devices have a freshwater tank and a wastewater tank, while others combine the two.
Water is pulled out of the water tank and through the filters using an internal water pump.
The water filters of each brand and in each machine vary. The best reverse osmosis water filters typically have at least two filters. Typical filters you might see are a pre-carbon filter and sediment filter that remove things like bacteria, chlorine and chloramines. A reverse osmosis filter has an ultra-fine filter and removes contaminants such as heavy metals, pesticides and fluoride. And finally, a VOC carbon filter that removes volatile organic compounds.
The filtered water is then pumped into a water collection container, such as a jug or internal tank. The contaminants are returned to the wastewater tank or remain in the filters.
The wastewater tank is then removed and poured down the drain. While the drinking water is ready for consumption.
The water tank and water collection container should be cleaned weekly, and the device, depending on the manufactures recommendations, should be descaled once a month depending on how hard your water is and how often you use it. The filters should be replaced as per the manufacturer’s recommendations, typically every three to 12 months, depending on the filter type and your water usage.
Under sink units:
In hard water areas, it is recommended that water go through a water softener before being filtered through an under-sink reverse osmosis water filter.
When you turn on a tap attached to an under-sink reverse osmosis water filter, the water pressure pushes the water through the filters.
The water filters of each brand and in each machine vary. The best reverse osmosis water filters typically have at least two filters. Typical filters you might see are a pre-carbon filter and sediment filter that remove things like bacteria, chlorine and chloramines. A reverse osmosis filter has an ultra-fine filter and removes contaminants such as heavy metals, pesticides and fluoride. And finally, a VOC carbon filter that removes volatile organic compounds.
Filtered water is then fed out from the faucet ready for drinking, and the waste water is typically flushed down the drain.
The filters should be replaced as per the manufacturer's recommendations, typically every three to 12 months, depending on the filter type and your water usage.
What are the benefits of reverse osmosis?
Pure water: Coming in closely behind water distillers, reverse osmosis water filters can produce some of the cleanest drinking water possible.
Quick to filter water: Unlike a distiller, you can filter within minutes versus hours.
Less energy usage: With many reverse osmosis devices, you can filter around 2L of water within about 15 minutes. You could then turn the device off at the power outlet to save energy when not in use. However, with some devices, such as those that provide cold water, you cannot do this, increasing power consumption.
Hot and cold options: Some reverse osmosis water filters have inbuilt hot and cold water systems. If you are looking to replace your kettle or enjoy fresh cold water, then this is a great option.
What are the limitations of reverse osmosis?
Expensive filters: filters can be very expensive, especially if they need replacing regularly because of living in a hard water area or if you want to filter lots of water.
Filter recycling issue: Reverse osmosis water filters are typically housed in thick plastic. They can be difficult to recycle, and this can lead to large amounts of plastic waste.
Lots of wastewater: Almost all reverse osmosis water filters are notorious for producing lots of wastewater, both during the filtration process but also the cleaning/descaling process. This is something to consider if you are on a water metre.
Filters degrade over time: After a few months of filtering tap water through the units filters they become less efficient. This is because contaminants are trapped within the filter making it harder for water to get through.
Plumbing: If you are looking to install a reverse osmosis water filter under your sink, it may require a plumber.
Potential for leaching contaminants: There have been situations when some devices have reportedly leached contaminants from the filters.
Plastic units: When looking for a reverse osmosis water filter you should ideally look for one that does not store the filtered water within a plastic water collection container. For example, a plastic jug or internal tank.
Difficult to repair: While external parts, such as tanks and jugs are typically replaceable, the internal components are generally not. This could reduce the lifespan of the device, making it less sustainable.
Heavy containers: You need to be able to lift and manoeuvre the water tank, waste water tank and carafe of water, something that may be difficult for some people.
Who is reverse osmosis water filtration best suited for?
A reverse osmosis water filter is great for anyone who is concerned about the high energy usage of a water distiller but would still like top quality filtered water. There are options for units of varying sizes and under-sink options that, while require plumbing, are very easy to maintain long term. Because of the speed at which you can filter water, they are a great option for anyone who knows they will forget to put a water distiller on and be left without filtered water for hours.
Our top-recommended reverse osmosis water filters
Below are two of the reverse osmosis water filters that we have researched, tested and loved at The Health Puzzle HQ. The AquaTru carafe is the perfect reverse osmosis water filter for those looking for a compact, high-quality water filter with a glass carafe. While the Waterdrop A1 has a larger water tank, and can dispense filtered hot and cold water into a vessel of your choosing.
Click the button below to check out our latest AquaTru and Waterdrop discounts and deals
3) Gravity-fed water filters
What is a gravity-fed water filtration system?
A gravity-fed water filtration system is a type of water filter that uses gravity (the natural downward pull of water) to move water from an upper container, through a filter element, into a lower container — without needing electricity or external pressure.
How does a gravity-fed water filtration system work?
Pour untreated water (from a tap, well, rainwater, or river) into the top container.
The water slowly passes through filter cartridges (usually ceramic, carbon, or composite filters). These elements trap bacteria, protozoa, sediment, and sometimes reduce chemicals, heavy metals, or bad tastes/odours depending on the design.
Clean water collects in the bottom chamber, ready for drinking, cooking, or other uses.
What are the benefits of gravity-fed water filtration?
No electricity needed: the device uses the power of gravity rather than electricity.
No plumbing: Easy setup that does not require a plumber.
Portable: easy to transport, lightweight when empty.
Quiet: no annoying pump noise.
Easy to clean: The basic system that is simple to clean.
Easy to repair: A simple system that can often be repaired with spare parts from the manufacturers.
Filters typically last a long time: Low pressure on the filters means that gravity-fed water filters typically last a long time. However, this depends on the filter size and water capacity.
What are the limitations of gravity-fed water filtration?
Slow filtration: not suitable for large quantities of water or lots of people
Filters degrade over time: After a few months of filtering tap water through the units’ filters they become less efficient. This is because contaminants are trapped within the filter making it harder for water to get through.
Potential for leaching contaminants: There have been situations when some devices have reportedly leached contaminants from the filters.
Who is gravity-fed water filtration best suited for?
Gravity-fed water filters are most suitable for people who need reliable, low-maintenance water purification without electricity or plumbing. There are ideal for off-grid settings as well as providing safe water in an emergency.
Our top recommended gravity-fed water filters
Three devices to choose from: the British Berkefield or Berkey gravity-fed water filters and the glass Brita jug.
Click on the images above for links to read more and purchase each gravity-fed water filter.
Final thoughts: What is the best type of water filter?
From researching and testing each type of water filter, it has become clear that you get the purest water using a water distiller, with reverse osmosis a close second.
While water distillers take longer to distil water, and they require more energy to run, they are easier and cheaper to clean and maintain. Reverse osmosis devices, on the other hand, offer the greatest flexibility, such as variable water tank sizes, hot or cold water dispensing and faster filtration times. The main downsides of reverse osmosis devices are that they can be more time-consuming to clean, they create lots of wastewater and the filters can be very expensive to replace.
While gravity-fed water filters have their place, such as for those looking to get started or looking for a power-free option, they do not remove as many unwanted contaminants as distillers and reverse osmosis water filters.
Want to learn more? Check out the following posts below:
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