Water Filter Technologies

Most people researching water filtration technologies are looking for more information on reverse osmosis, activated carbon block filtration, and gravity-based granulated carbon filters. These are the three most popular water filtration methods available for residential consumers and most of us just want to know which one is the best. The answer to that question, however, is not so simple. Depending on where you live and what is in your water, as well as your preference with regards to complexity of installation, water taste, wastewater, specific contaminant removal, and initial and ongoing cost, the filter technology that best fits your needs may not be the best for someone else. The real question we need to ask when researching water filtration systems and technologies is, “Which is the best filtration method (and system) for me?”

Gravity-based granulated carbon filters

One of the most common filtration methods used in homes is gravity-based granulated activated carbon. This is the filtration technology used in most drip pitcher filters and dispensers: think Brita pitcher. Gravity-based filters are seen as “entry level” filters. The initial purchase price is low and they are widely available in most big retailers and grocery stores. Pitcher filters are portable and convenient, but gravity-based filtration is generally the least effective filtration method on the market – typically they only remove 5-10 contaminants, which is very low compared to almost every other filtration method out there. Pitchers and dispensers that use gravity to slowly trickle water through the granulated carbon media typically remove chlorine taste and odor and a few other easily removed substances. While pitchers are easy to use and require no installation, they typically are slow and cannot produce large quantities of filtered water. Gravity-based pitcher and dispenser filter cartridges also need to be replaced generally every 1-3 months to still be effective. Frequent filter replacements not only require more maintenance, but will also drive up ongoing cost. In sum, gravity-based granulated carbon filters are convenient and portable, but are not that effective at actually filtering the contamination out of your water.

Carbon block filtration

Another filtration method commonly used in homes is carbon block filtration, also known as activated carbon. Carbon block technology is used in most under counter and faucet-attach point-of-use (POU) systems. Carbon block filtration differs from gravity-based granulated carbon filtration in that it uses water pressure to force water through a densely packed carbon block, instead of letting gravity trickle water over loose carbon granules. Greater contaminant removal and faster filtration is achieved with POU carbon block filters. However, not all carbon blocks are created equal. Carbon block filters with micron ratings less than 1-micron in size are capable of reducing the most contaminants due to their tiny pore structure that captures microscopic contaminants that can simply pass through a gravity-based pitcher. Carbon block filtration generally removes between 50-60 contaminants as opposed to just 5-10 contaminants for gravity-based filtration. A major benefit of carbon block filtration is that it is capable of reducing chemicals and contaminants from water while also leaving in beneficial, naturally occurring minerals ideal for drinking and hydration. These minerals, like calcium, magnesium, and potassium are what give water that naturally clean spring taste. In sum, if restoring water to its most natural state by removing contamination and chemicals is most important to you, you’ll want to get a high performance carbon block POU system.

Reverse Osmosis

Initially developed to turn salt water into potable drinking water, reverse osmosis technology has grown in prevalence in recent years.  Like carbon block filtration, reverse osmosis (RO) technology uses the water pressure in your pipes to force water through an RO membrane with an extremely small pore size – thus removing a large number of dissolved solids.  Unlike carbon based filtration technologies, RO systems produce wastewater, an unavoidable side effect of the reverse osmosis process. Most RO systems waste over 50% of the water that passes through them.  Reverse osmosis systems usually have a basic carbon block as the first stage to remove chlorine as chlorine will destroy the RO membrane over time.  This basic set-up is effective at removing some very specific substances in your water, notably, dissolved solids like sediment, salt, nitrates and minerals.  It is also effective at removing metals like lead, fluoride and arsenic. What the physical membrane will not remove is much of the chemicals that may be in your water like volatile organic chemicals (VOCs), herbicides, pesticides, and pharmaceuticals.  To remove these chemicals you need to add additional advanced carbon block filters.  Basic RO systems remove about 14 contaminants.  When combined with advanced carbon block filters they can remove over 70 – more than any other single water filtration method out there.  To get this level of filtration though, there are a few tradeoffs.  First, RO systems remove all dissolved solids, including naturally occurring minerals that typically make your water healthier and better tasting.  The removal of these minerals also lowers the pH of the water and can make the water more acidic than it would naturally be.  Some RO systems offer remineralizers to add minerals back in to increase pH for more alkaline water and better taste.  Second, all RO systems waste water.  It is an unavoidable part of the RO process. Third, the installation process is a bit more involved due to the extra tank and water drainage requirements. Finally, reverse osmosis system tend to be expensive compared to other available filtration methods.  In sum, RO systems are a good solution if you want to remove dissolved solids like fluoride.  The best RO systems include a high performance activated carbon filter after the RO membrane to remove the chemicals reverse osmosis won’t, and will include a remineralizer to restore the pH balance of the water and improve taste.