Let’s separate this post into two categories:

  • Important factors for drinking water safety
  • Important factors for easy, convenient filtering

I’d recommend separating these two aspects out as it’s definitely possible to have one without the other. As any hiker or backcountry camper knows, today’s technology makes it relatively easy to produce clean, safe water from some truly disgusting sources. Filter brands like LifeStraw and Sawyer have become globally popular for their simple yet powerful suction mechanisms.

But we can confidently say that most people won’t be relying on a manual filtering system inside their own home. In fact, most home filtering systems are not primarily designed for ensuring water safety at all. As we’ll discuss, your average activated carbon filter is all about giving you easier access to better-tasting water, rather than remove potentially harmful contaminants.

Let’s start with the safety conversation:

Important factors for drinking water safety

The factors you’ll want to consider when choosing a water filter for safety ultimately come down to the quality of your mains water supply.

For the majority of readers of this post, water safety isn’t something you need to worry too much about. According to WHO, 71% of the global population had access to safe drinking water in 2017. That means water that’s local, on-demand, and uncontaminated (and the number rises to 90% if you count more basic forms of access.)

More locally, this comprehensive article from The Conversation picks up on EPA chairman Andrew Wheeler’s claim that 92% of drinking water in the US is safe to drink, straight from the tap. Whether you consider this a good or bad percentage (and how you rate the health of America’s public water systems more generally) is probably a matter of perspective, but the fact is that the overwhelming majority of drinking water across the country is pretreated by well-established methods, such as chlorination and ozonation.

However, thanks to high profile disasters and political issues such as the ongoing dispute at Flint, Michigan, we all know that modern, well-developed water infrastructure is never a 100% guarantee of water quality. Add this to the reality that many of us live in buildings with old, corroding, and lead-containing pipes, and you may come to the conclusion that it’s not enough to simply trust in official statements about the water coming into your home.

Instead, many are investing in home filtering devices capable of doing the job of a more industrial system. These models cost upwards of $350 for an under-sink model, and can easily stretch into the thousands of dollars for a whole-home filter, and normally include multiple stages of filtering. Of the stages that ensure water safety, the most common two are Reverse Osmosis filtering and UV purification.

Reverse Osmosis

Osmosis describes the natural tendency for water and other solutions to cross membranes in the direction of more-to-less dense solutions, finding equilibrium. An RO filter works in the opposite direction, applying an external force to send tap water through a filtering membrane before it reaches the faucet.

RO filtering will remove disease-causing protozoa such as cryptosporidium and giardia, bacteria like E. coli, and viruses like the norovirus. According to the CDC, they’ll also deal with potentially harmful metals like chromium and lead, and may or may not filter for arsenic and potassium, depending on the specific model.

Domestic reverse osmosis filter

Ultraviolet Radiation

By exposing water to a UV lamp, this process renders any potentially harmful microbes inactive, disrupting their biology on a cellular level. In this sense, ultraviolet treatment is a purification rather than a filtration process, meaning that it’s almost always paired with an additional filtration stage.

Ultraviolet treatment alone is not effective in inorganic compounds, so it won’t remove chemicals, as confirmed by the same CDC article.

Read: Which Water Filter Removes the Most Contaminants?

Important factors for easy, convenient filtering

Those established methods of creating safe drinking water we mentioned above—chlorination, ozonation, etc—are great developments for general public health. But they’re not so great when it comes to the purity and taste of our tap water. Add those chemicals to the high levels of natural (and safe) sediment found in hard water areas, and you get an incoming water supply that just does not taste good.

Better-tasting water is the primary motivation for home water filtration. If you’re looking for a filter that may not serve as the last line of defence against harmful contaminants, but will improve your daily enjoyment of tap water, then the factors you’ll want to focus on are the ergonomics of your filter, and filter base price vs maintenance costs.

Filter placement

What does your kitchen setup look like? Do you have the space to add a countertop filter into the mix, or would a pitcher style filter that you can store in the fridge keep things tidier and more organized? Some might call this overthinking, but if you’ve reached the point where you’re reading filter-buying advice online, you’re probably not one of those people!

More seriously, if you can foresee repeatedly carrying a pitcher filter over to the sink for multiple daily refills becoming tedious, then you probably want to look at options for attaching a filter directly to your faucet, as you want to encourage as much filter use within your home as possible. Filters can be installed at the point of use either by mounting then to the tap, under the sink, or on the countertop.

Maintenance vs base price

When the difference in price between a simple pitcher filter and a full point of entry (POE) filtering system is literally many thousands of dollars, it’s important to make a purchasing decision based on how you actually plan to use the filter, as well as foreseeing any costs related to upkeep and maintenance. According to consumer reports, for example, the cost per year to replace the cartridges in a simple 50 dollar pitcher can be anything from 30 to 90 dollars.

Likewise, an under-sink filter may cost a lot more at the outset, but you’ll only be replacing components on a yearly (or longer) basis. Plus, you can do away with those annoying refills. The question being, is it worth paying more at the point of purchase for an easier, more seamless daily experience?


When choosing a new filter, ask yourself whether you’re more interested in producing guaranteed safe drinking water, or if your aims are more to do with improving taste and convenience. Getting clear on that choice will immediately narrow down your options, letting you focus on either:

  • The pros and cons of multi-stage filters, or
  • The decision between sink-side and portable carbon filters

Read: Here’s our full in-depth comparison of the different types of water filter.