Congrats! You made the switch to a refillable bottle. Big win! You are officially part of the solution to the world's plastic crisis. But now comes the next big question, what kind of water are you actually #refillit with?
Sometimes it can feel overwhelming with how many filter options on the market and the health alerts we keep hearing about. We know there’s a lot to consider when you think about your drinking water.
So let’s peel the curtain back and take a simplified approach to understanding which water filters might be the best for us.
How to understand your tap water
Let’s start with understanding our tap water. Most municipalities treat water to a safe level for drinking. Depending on where you’re located, that could look different since we all have different sources for our tap water. Some tap water like in New York City, comes from the Catskill Mountains and the Hudson River Valley. NYC has notoriously delicious and safe to drink tap water. San Francisco tap water comes from the pristine Hetch Hetchy Reservoir in Yosemite National Park. Again, great tasting, soft and safe to drink straight from the tap.
Now even if the local tap water is high quality, it’s important to consider what pipes that water travels through in order to get to your water source. Some older buildings have corroded pipes that can get into your tap water, and this is the main reason why we want to have a safeguard filter before drinking.
While tap water is cleaned and safe from EPA regulated contaminants, there are also microplastics and PFAS (commonly known as "forever chemicals") that are new to consider.
A report by the Environmental Protection Agency (EPA) concluded that PFAS contamination is documented in surface water, groundwater, soil, and air across the U.S., from rural to urban communities. Because these chemicals are so widespread, the EPA has established evolving federal health advisories and standards for PFOA and PFOS (the most common types of PFAS). They are aggressively tackling this issue through their strategic roadmap and outlining new goals in the office of water priorities. The USGS also actively monitors how these emerging contaminants impact our broader water supply.
If you aren't sure about your pipes or your local water quality, don't panic. You can easily check your local state’s drinking water system and any violations using the EPA's public reporting system. Another fantastic, user friendly tool is the EWG Tap Water Database. Just type in your zip code then click on your water department to see exactly what is flowing through your local water systems AND the software will also suggest specific filters based on your location. Great resources there!
How should refillable bottle water users think about filtration?
When you carry a premium PATH bottle, you want to fill it with the cleanest, safest water possible, but walking down the water filter aisle can be incredibly confusing.
The core concept you need to understand is that water treatment technologies vary significantly. Filters work differently based on the contaminant type they are targeting, their microscopic pore size, their adsorption chemistry (how well toxins stick to the filter material), and their overall system design. Many advanced systems actually combine multiple technologies to give you the best of all worlds.
How you want to think about your water is by first considering your location, then your home’s capabilities to integrate an entire filter system, or whether having a water filter pitcher will be your best option.
A comprehensive guide by the Centers for Disease Control and Prevention (CDC) concluded that no single home water treatment system removes every single contaminant, meaning you must choose a filter based on what is actually happening around your local water. The EPA Home Water Treatment Guide agrees, stressing the importance of doing your homework first.
Point of use versus whole home filtration systems
There are 2 water filtration systems to consider, one is point of use and the other is a whole home filtration system.
Whole home filtration systems are installed at your main water line, cleaning all the water that enters your house. However, there is a catch. Because they remove municipal disinfectants (like chlorine) right at the front door, they can actually increase the risk of microbial and bacterial growth inside your home's indoor plumbing.
Point of use systems treat water right at a specific tap, like an under the sink system or a refrigerator pitcher. For someone looking to safely fill up their daily water bottle, a point of use system is usually the simplest and most cost effective choice.
What are PFAS and what actually works for filtering PFAS?
PFAS are man made chemicals used for decades to make things non stick, waterproof, and stain resistant. They are designed to be tough, and do not easily break down in the environment or in our bodies.
Children are especially sensitive to PFAS exposure because their bodies are still developing. The EPA uses highly advanced testing methods, like 533 and 537.1, to detect these invisible chemicals, and they provide practical steps you can take to reduce your daily exposure.
What actually works for filtering PFAS?
If you want to clear these "forever chemicals" out of your drinking water, you have a few options.
Reverse Osmosis (RO)
This is the gold standard for home filtration. A study by North Carolina State University (NCSU) concluded that under the sink reverse osmosis systems have a typical removal efficiency of up to about 99% for a broad spectrum of PFAS, including the tricky short chain varieties.
Granular Activated Carbon (GAC)
These carbon filters can remove 20% to 55% of PFOA and PFOS.
Ion Exchange Resins
Ion exchange resins are recognized by the EPA as effective for PFAS removal, especially short chain compounds that carbon based filters miss.
Emerging Materials (such as LDH)
Emerging materials like layered double hydroxides (LDH) are a new type of filter material that grabs PFAS chemicals out of drinking water and holds onto them so they cannot pass through. Scientists at Rice University built a version using copper and aluminum that is 1,000 times better at catching one of the most common PFAS chemicals than other materials tested, pulls it out of the water 100 times faster than the carbon filters most people are familiar with, and can actually destroy the chemical completely instead of just storing it.
What are the most effective PFAS filtration technologies?
Other filters that remove PFAS
Gravity Filters (like Berkey)
These countertop systems operate by simply letting water slowly drip through incredibly dense, microscopic carbon filters using gravity. They are great for filtering large batches of water without needing to mess with your home's plumbing.
Specialty Pitchers (like Clearly Filtered)
Not all pitchers are created equal, but advanced pitchers use advanced filtration technology to actively grab and hold onto forever chemicals. You can check out the EWG's guide to PFAS water filters to find the best pitcher for your home.
PFAS filtration new development
Scientists have recently created a new kind of filter that can grab and break down PFAS “forever chemicals” much faster than today’s filters. Tests show it can work about 100 times faster than standard carbon filters, so if it scales up, it could really change how we clean drinking water in the future.
What actually removes microplastics?
While PFAS behave like dissolved chemicals in water, microplastics are tiny solid bits of plastic that stay as particles and can be physically strained out. Removing them depends on using filters with pores small enough to catch these particles rather than just media that adsorb dissolved contaminants.
Ceramic filters are a strong option for this kind of particle removal. Low cost ceramic filters typically remove about 95% to 99% of cloudiness in the water, bacteria, and suspended solids through a mix of physical straining in their fine pores and electrostatic interactions at the surface, which also helps trap many microplastic particles of similar or larger size. They function like a very fine, porous barrier that blocks particles while letting clean water pass through.
Many ceramic filters mix in extra ingredients like lanthanum, silver, or zinc oxide so they can grab germs and certain chemicals more strongly and help stop bacteria from growing inside the filter. If your pitcher or under the sink system can use ceramic cartridges, choosing ones that have been independently tested to remove very small particles and germs will also help with microplastics and other water issues, and if you use a system that accepts them, the PATH pure filter replacement is one ceramic option the company offers for that kind of setup.
What removes both PFAS and microplastics?
If you want one system that goes after both dissolved chemicals, such as PFAS, and tiny particles like microplastics, a reverse osmosis (RO) unit is one of the most comprehensive options. RO systems push water through a very tight membrane that acts like a barrier, blocking most particles (including many microplastics) and reducing many dissolved contaminants at the same time.
Guidance from the CDC and EPA explains that well designed RO systems can remove parasites, bacteria, and viruses and can greatly reduce many dissolved chemicals, including lead, copper, chromium, arsenic, fluoride, and nitrate. The EPA also lists high pressure membranes such as RO among the most effective technologies for PFAS treatment, and research on drinking water RO systems has found PFAS removal typically above 90% to 97% when the membrane and prefilters are properly maintained. Studies of membrane based devices further show that these systems can remove most microplastics by size exclusion, though trace amounts may still pass through tiny defects or aging membranes.
Because RO is so good at taking things out, it also strips out many natural minerals like calcium and magnesium that affect both taste and mineral intake. For that reason, many people who use RO choose some form of remineralization, such as adding a remineralization cartridge after the reverse osmosis unit or using mineral drops or mineral rich salts, to bring some beneficial minerals back into the water.
The big takeaway for refilling your bottle
When choosing a filter to refill your bottled water, keep these simple rules in mind. If your primary concern is physically removing microplastics, look into high quality ceramic filters or a reverse osmosis system.
If your main concern is cutting down invisible PFAS chemicals, look for a certified reverse osmosis system or a more specialized advanced pitcher.
You have already made a strong choice by protecting the planet from plastic waste. Now, pair that with the right water filter, grab your durable PATH bottle, and refill it with confidence as many times as you can.
Shop our preferred clay filter here >