Undersink water filters are stored in the cabinet under your sink, and attach directly to your coldwater line. Underink filters remove contaminants at the point of use, making them one of the more effective types of water filtration. The surface area for most undersink water filters, including Hydroviv’s, is large enough to allow for enough contact time with incoming water to allow for sufficient filtration.
Hydroviv filters take this a step further. Because contaminants in tap water can vary state by state, and even by zip code, Hydroviv creates custom water filters that are tailored to remove contaminants in your specific tap water.
There can be some downsides to this type of water filtration. For example, some companies require a “designated faucet” just for drinking water. You would need to drill a hole in your existing countertop if you don't already have one to attach the filtered water to. When searching for undersink water filters, you'll want to look at technical specifications to see if you'll need a designated faucet.
This style of filtration includes pitcher-style filters like Brita and countertop systems like Berkey. Most gravity-fed and pitcher filters do a really good job removing chlorine, but not much else. The performance of these types of filters is directly related to the speed at which water flows through the system. If a gravity-fed system claims “fast filtration,” you’ll want to take a closer look at its specifications. For this style of filtration, you actually want longer contact time with the filtration media. If your drinking water has things like lead, chromium 6, PFAS, and other harmful contaminants, gravity-style filters are not for you.
Faucet filters, like a Pur Filter, clip on to the end of your faucet. This type of water filtration can be a bit unsightly, which is why we sometimes refer to them as “faucet warts” in-house. There are several conditions that can cause faucet filters to fail. First, lead levels in unfiltered incoming water could be higher than what the filter had been tested at in a lab. NSF certified faucet filters are tested at 150 parts per billion. However, lead levels in New York City, Flint, Michigan, Newark, New Jersey have been detected well above 200 parts per billion. Second, the water could be flowing faster than it was rated for, preventing sufficient contact time with filtration media. Finally, their size does not make for significant removal capacity. If your water has a variety of harmful contaminants, the lead-removal capacity can be significantly reduced.
Case Study: Newark, New Jersey distributed Pur end-of-faucet filters to residents during the summer of 2019 after the city discovered that it was in exceedance of the federal Action Level. The filters provided by Newark city officials did not remove lead. Click here to learn more.
Whole House water filters are a good option for only a very small percentage of households. Whole House water filters do not remove chromium 6, arsenic, and lead. People are often under the assumption that filtering water at the point-of entry is the most efficient and easiest way to ensure clean water. Unfortunately, this is not the case. First, flow rate at the whole house level is extremely fast and does not allow for sufficient contact time with filtration media, resulting in limited contaminant removal. Second, when you remove chlorine at the point of entry (whole house), bacteria can build up in the pipes and water tanks. Third, about 90% of the water filtered at the whole house levels gets flushed down the pipes. However, if you have a private well with a serious sulfur problem, a whole house water filter might be the solution for you.
Reverse Osmosis or RO water filters use a type of filtration technology that pushes water through a semipermeable membrane to remove contaminants. The term "reverse osmosis" describes the technology used, but it does not indicate anything about the performance of the system. If you’re a renter or have a recently installed granite countertop, RO is probably not an option for you. There’s a ton of variability when it comes to filtration performance, so you’ll definitely want to ask for third party test data when shopping for an RO water filter. There are a lot of other downsides to reverse osmosis, aside from the steep cost. First, your water usage will go up significantly, as well as your monthly water bill. Most residential RO systems require 3-15 gallons of unfiltered water to generate 1 gallon of filtered water. Second, the pre-filter membrane must be changed frequently to prevent chlorine from “backflowing” into finished water. This often happens without the homeowner even realizing, and is very expensive to fix. If you are however dead set on RO, we recommend going with this Apec system.
Most refrigerator filters are typically designed to simply improve the taste of drinking water, not to actually remove harmful contaminants. Most fridge filters are built into the refrigerator upon purchase. When you don't change a fridge filter cartridge according to manufacture specification, the cartridge can over-saturate and cause contaminants to leak in "filtered" water. We hear from folks all the time who haven't changed their fridge filter cartridge in years because refrigerator companies give very little guidance on when and how to do so. A recent Duke University PFAS filtration study highlighted various fridge filter brands that put harmful contaminants back into filtered water.
When purchasing a water filter, you’ll want to consider something a bit more robust. This is especially true if you have young children that use the fridge spigot for drinking water. Children are most susceptible to health impacts associated with exposure to contaminants such as lead, chromium 6, and PFAS. Hydroviv makes a refrigerator system that can be installed in an adjacent cabinet or before your fridge.