What Is The Difference Between A Water Softener And A Water Filter?
Think your water filter will soften your water, or that your water softener is filtering impurities out of your water? Think again, water softeners and water filters serve very different functions and should not be mistaken for one another.
In some cases, a water filtering system such as a reverse osmosis (RO) system will remove hardness-causing minerals from the water, most sediment and charcoal water filters will not do so, leaving the water hard.
Similarly, ion-exchange water softeners that remove and replace scale-forming minerals calcium and magnesium from the water supply will remove few, if any, other dissolved minerals and almost no sediments, solids or bacteria.
Some water conditioners, often referred to as salt-free water softeners, will filter out other minerals as the water passes through the hardness-conditioning cartridges, but this will be more by accident than design, unless the conditioner is also fitted with purpose-specific filters containing activated carbon or other filtering media.
Electromagnetic scale inhibitors, also sometimes marketed as salt-free water softeners, will have absolutely no filtering effects, since they do not in any way physically interact with the water that they are treating.
What Are Water Filters? How Do They Work?
Water filters are used to improve the quality and purity of water supplies, making it safe for human consumption (or other uses that need clean, pure water, such as industrial boilers).
They generally use one or more physical barriers to inhibit particles, down to micron size, from passing through them with the water supply.
Water filters come in a range of different types, with differing functions. Some of the more common ones that are used in household water filtration are granular activated carbon (charcoal/GAC), hollow fiber (HFM), ceramic filtering, reverse osmosis (RO) and ultraviolet radiation (UV).
Activated carbon filters use a process of ‘adsorption’ to trap contaminant molecules inside the pore structure of the carbon particles, removing them from the water source.
Carbon filters are effective in removing certain volatile organic compounds (VOC’s), chlorine, sediment, unwanted tastes and odor, as well as fluorine and radon. They are much less effective at removing salts, minerals and dissolved inorganic compounds.
Activated carbon filters may suffer from a growth of bacteria over time, owing to their pores becoming clogged and water flow being reduced. Options to address this problem are the inclusion of metallic silver nanoparticles in the filtering element, or post-sterilization of the water (see UV filtering below).
Hollow fiber membrane (HFM) water filters are used to effectively remove turbidity (fine sediment, dissolved solids) and bacteria from water supplies, often in conjunction with activated carbon filters.
Bacteria are generally 0.2 to 3 microns in size, less than the 75 micron thickness of a human hair or even the 5 micron size of a human blood cell.
Ceramic filters have a pore size of 0.22 microns and suffer from the same potential for clogging and bacterial growth as activated carbon filters. They are typically used to remove bacteria and microbial cysts, but some chemicals and viruses are small enough to pass through their pores.
These filters may also have added silver to combat the growth of algae. Ceramic filters tend to be relatively slow at filtering water.
Filters should contain a chemical disinfectant matrix to be effective against viruses. However, many people do not want chemicals added to their drinking water.
Reverse Osmosis (RO) represents a more complex form or water filtering, as it requires pressure to force the water molecules through the porous membrane filter system. This can either be the water supply pressure, or it can be augmented by a pressure pump.
Owing to the small pore size of the membrane, at down to 0.0001 of a micron, the RO system will remove bacteria, minerals and dissolved solids from the water. Because RO systems filter such fine particles out of the water, the membrane/s tend to need rinsing out more frequently than other filter types.
Fortunately most RO systems are equipped with an automatic rinsing system which backwashes water at pressure through the membrane in the reverse direction, washing most of the filtered particles off the membrane surface and the resulting waste water is flushed away. The RO system thus uses some of the filtered water it uses to flush itself and is therefore relatively wasteful of water.
In addition, RO systems usually incorporate other forms of filtering, including activated carbon, to improve efficiency, adding to their cost.
Many water filtering systems include an ultraviolet (UV) sterilization filter after the other filtering methods, in order to neutralize any remaining microbial contaminants in the filtered water. The UV filter works by shining a light at a specified (ultra-violet) frequency band through the water.
The UV light disrupts the DNA of any bacteria or virus present in the water, so that they become inactive. It is important that suspended solids, which could shield organisms from the UV light, are removed from the water before the UV filter, hence it is usually the last form of water treatment in the process.
Water Softeners. Why Do You Need One?
Water softeners, in contrast to water filters generally, have the function of only removing or treating hardness-causing minerals calcium and magnesium and, to a lesser extent, ferrous iron and manganese.
This is achieved either by ion-exchange, or, in so-called salt-free water softeners/conditioners, by chemical or physical (electromagnetic) treatment of the hardness ions in the water.
The purpose of using a water softener is to leave the water less prone to causing lime-scale buildup in, electric water heaters, pipes and fittings, to improve the cleaning properties of soap and shampoo, and to reduce the incidence of soap-scum.
Water softeners do not generally remove solids, dissolved solids, bacteria or viruses from water, and do not make water cleaner or safer to drink.
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