Per- and polyfluoroalkyl substances, known as PFAS for short, are a group of more than 4,000 manmade chemicals that have been used in industrial processes since the 1940s. If you’ve clicked on this article, I’m guessing that you’re already familiar with PFAS and the serious health risks they pose.
Because PFAS are known as “forever chemicals”, it’s not easy to eliminate these contaminants at their source, despite the fact that they’re no longer used today. This means these chemicals can end up in our drinking water.
Reverse osmosis is one of the best treatment options for removing Per- and polyfluoroalkyl substances (PFAS) contaminants from water.
In this guide, I’ll tell you what you need to know about reverse osmosis for PFAS, including the effectiveness of this solution, any RO setbacks, and considerations to make when purchasing an RO filter. I’ll also offer an alternative PFAS-removal option if you don’t think reverse osmosis is quite right for you.
Table of Contents
💧 How Does Reverse Osmosis Filter Out PFAS?
Reverse osmosis filters force water through a semi-permeable membrane. This membrane has a pore size of around 0.0005 microns, meaning that any impurity that’s larger than this micron rating will be unable to pass through the membrane with water particles.
The average PFAS chemical is much larger than 0.0005 microns, making RO an effective option for removing this contaminant.
When PFAS, PFOA and PFOS (and other contaminants) collide with the RO membrane, they bounce back. During the RO process, a small amount of water is flushed down the drain in the chamber that holds the RO membrane. This prevents a build-up of contaminants in the RO chamber.
A typical RO system will have multiple filtration stages as well as the RO membrane. One of these filters is a carbon filter, which is capable of removing approximately 73% of PFAS from water. Combining both the carbon filter and the RO membrane gives you the most effective overall PFAS-removal solution.
Related: Do carbon filters remove PFAS?
📊 How Much PFAS Does RO Remove?
Reverse osmosis is incredibly thorough, and the best RO systems can remove more than 90% of all PFAS contaminants – so that should certainly help you to reduce your PFAS levels to below the Environmental Protection Agency ‘s health advisory level of 70 parts per trillion. This is about as good as it gets if you’re looking to remove PFAS, PFOA and PFOS from your water with an at-home filtration unit.
🧫 What Else Do Reverse Osmosis Filters Remove from Drinking Water?
If you’re looking to remove PFAS from drinking water, there’s a good chance you’re concerned about other contaminants in your water, too. RO can remove contaminants like chlorine, bacteria, viruses, heavy metals, fluoride, VOCs, minerals, salts, and pharmaceuticals up to 99.9% effectiveness.
It’s easier to say what reverse osmosis systems don’t remove – hydrogen sulfide and other dissolved gases might be able to slip through the RO membrane, and some solvents, VOCs and pesticides may also remain in your water after using RO water filters.
👎 Drawbacks With RO Systems
While RO systems are incredibly effective at removing PFAS and other harmful drinking water contaminants, there are a few setbacks of these systems to keep in mind:
Higher Price Tag
Because RO is so capable, you should expect to pay more for this type of water treatment solution. It’s common for an RO system to cost upwards of $300 – and that doesn’t include the yearly maintenance costs.
Wastewater is Produced During Filtration Process
Whether you’re using point-of-entry (such as whole-house systems) or point-of-use filters, your RO system will waste some water during the water treatment process. There’s no way to get around this, unfortunately, though newer systems are far more efficient than they used to be.
Healthy Minerals Removed
Though there’s no denying that RO water treatment is incredibly beneficial, a big setback is that these water filters also remove healthy minerals from tap water. If you want to add these minerals back into your water, you’ll need to find a unit that comes with a remineralization water filter, or purchase mineral drops.
Maintenance to Keep Up With
Finally, RO water treatment requires regular maintenance in the form of cleaning and replacing the filters. If you want your RO system to continue working at a high standard, this maintenance is unavoidable.
💭 Reverse Osmosis System Purchase Considerations
When looking for an RO system, make sure to consider the following:
Efficiency Produced Water to Wastewater Ratio
I mentioned earlier that all RO filters produce some wastewater, but some produce more than others. Though the earlier RO systems used to waste 4 gallons of water for every 1 gallon of clean water produced, nowadays, you can find systems that only waste 2 gallons of water for every 1 gallon produced.
Some systems even have a 1:1 wastewater to pure water ratio, which may be worth looking at if you want to waste as little water as possible.
Your Home’s Water Quality
The quality of your drinking water – i.e. the chemistry and contaminants present – is something to keep in mind when you’re considering which system is for you. The more contaminants your water contains, the harder your RO system will have to work.
Even if you just want to get rid of PFAS chemicals, your RO membrane will still tackle everything it comes across. You’ll probably need to replace your filters and membrane more frequently than advised by the manufacturer as they’ll become clogged within a shorter time frame.
There are several different types of RO system to choose from. Point-of-use filters, like the under-sink reverse osmosis filter, are the most popular option if you just want to remove PFAS from your faucet’s drinking water.
Whole-house systems are harder to come by compared to point-of-use units. The benefits of whole-house filtration are certainly worth considering, but research has found that whole-home treatment may leave your pipes and plumbing more susceptible to bacterial growth.
Finally, countertop RO systems are also effective at reducing PFAS levels in the water. Your treatment options are widely variable when it comes to RO, so you’re bound to find something that suits you best.
No matter what you go for, all RO systems remove pretty much the same level of contaminants, so if you want to avoid the health effects of PFAS, RO treatment is the way forward.
Your budget will determine the kind of filtration system you can buy. There are some systems, such as whole-house systems, that may not be within your budget.
You’ll also generally need to pay more for RO systems that waste less water, tankless systems, or systems that feature more than 4 stages (which is pretty much the average for an RO water filter). The most affordable RO option is the tank-based under-sink reverse osmosis system.
If you want to buy a high-quality system that’ll last, you’ll need at least $200-$300. Don’t be tempted to pay less for a system that’s lacking in quality, as it may not even do a good job at removing PFAS – the reason you want to buy it in the first place.
❕ Alternative Consideration: Activated Carbon Filters
If you don’t think your budget can stretch so far, a great RO alternative is activated carbon.
Activated carbon filters can remove high levels of PFAS chemicals (approximately 73%). Though they might not be quite as effective at removing these contaminants, the major advantage of these filters is that they cost a fraction of the price of RO filters.
However, this does depend on the type of activated carbon filter you buy. When tested, systems varied widely- some filters removed a high level of PFAS from drinking water, while others removed virtually none.