What is reverse osmosis water filtration? What is the best reverse osmosis water filter available in the UK?
- Josie Shillabeer
- Aug 31
- 5 min read
Updated: Oct 20
Learn how reverse osmosis water filters work. Plus, check out our top recommended reverse osmosis water filters available in the UK.
What is reverse osmosis water filtration?
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.
Best reverse osmosis water filter
Best looking filter, largest water capacity, cheapest annual costs
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This article is made up of text taken from two previous post from The Health Puzzle. The first is https://www.thehealthpuzzle.co.uk/post/the-best-type-of-water-filter and the second https://www.thehealthpuzzle.co.uk/post/the-best-countertop-water-filters-uk.
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