In Part 4 of our 10 part series How to Choose a Water Filter, I left you hanging with a burning question. What in the world is KDF? So let’s get right to it; KDF (Kinetic Degradation Fluxion) is a high purity copper zinc alloy. Please note: an alloy is a completely unique metal. Once the alloy is created it ceases to be either copper or zinc, and is now KDF. No copper or zinc are added to water filtered with this special media. Technically speaking KDF reduces and oxidizes contaminants. It doesn’t really capture them, but rather converts them by adding or removing electrons. It is basically a form of ionization. As a result, it is incredibly good at reducing chlorine, and even better at removing hydrogen sulfide (H2S) known for it’s rotten egg odor. Unfortunately it has one major weakness; KDF is extremely heavy. Typical KDF water filter cartridges have very poor flow rates and cause significant pressure loss. This isn’t a problem for point of use systems that only demand .5 to 1.5 gallons per minute (gpm), but it’s a huge problem for whole house water filters. Auto back washing systems utilizing KDF media typically require a minimum of 15 gpm for back washing. Depending on your circumstances, you may not be able to accommodate that flow rate. Cartridge based systems will usually need to be installed in a parallel configuration rather than in series which is much more common (see diagram below). This is necessary because most KDF filters are “axial flow”, and not the more common “radial flow” cartridge (see images below).
As you can see from these diagrams an axial flow cartridge forces the water to travel upward through the entire bed of media. This provides for superior contact time and greater contaminant removal than a radial flow cartridge, but with dramatically greater pressure loss and flow restriction. As previously mentioned this can be overcome by installing multiple water filters in a parallel configuration. Obviously this presents a higher initial cost and a more complicated plumbing project, as well as requiring more space. Having said all that, KDF is amazing at getting rid of that horrible rotten egg odor caused by H2S. Furthermore, many KDF filters are a combination of KDF and Carbon. These multimedia cartridges are very powerful for dealing with a variety of taste & odor issues, and are also useful for some high level contaminants that we will deal with in our next installment. If you have a stubborn taste & odor issue and haven’t yet tried a KDF or KDF & Carbon combo filter, it may be just the thing you need to finally conquer that stubborn water problem.
Be sure to check out our next installment where we will tackle high level contaminants like heavy metals, VOC’s, MTBE, pathogens and many more.