An In-Depth Comparison Of The Best Under Sink Water Filters

A water filter removes impurities from tap water using a variety of methods, including ion-exchange, adsorption, and activated carbon absorption. 

Under sink water filtration has the advantage of having an easy-to-clean filter that is easily accessible for most people. Filters can be installed under either mounted or drop-in sinks. Drop-in filters are usually used when countertop space is not available, but mounted sink filters may look better with a specific style of kitchen faucet. 

Under sink water filters change the standard filters every 6 months because of hard water. They need to be checked more often if their water is very hard (i.e., 175 ppm). Softer waters may only require changes once a year, but this should be done according to the manufacturer’s specifications. 

Under-sink water filters can be moved from one sink to another, making them more versatile than other types of countertop systems. Systems with easy-connect hoses make it possible for two or more separate sinks in a household to have filtered water. 

Some people do not like the look of a filter that is connected to a faucet or a hose, and others complain that water pressure may be lower if the filter is attached to the kitchen sink’s supply line. Water flow from an under-sink filter is slower than that of a system connected to the main water supply. 

Most under-sink filters do not have any special filtration technology that is designed to remove or reduce fluoride levels in drinking water, but some are now available with activated carbon. These filters may reduce up to 40% of the fluoride present in your tap water. 

Under-sink systems can be categorized as: 

1. Reverse osmosis (RO). RO water filters produce highly purified and nutrient-void H2O. Reverse osmosis systems have a high starting price but create water that is clear and odorless. Since they use a membrane as a filter, these filters also tend to be the most challenging to clean.
2. Activated carbon (AC). AC filters can remove chlorine from your tap water and improve its taste and smell. These units, however, are not designed to purify water; they simply work as small water softeners for impurities that affect the taste and smell of the water.
3. Enhanced filtration (EF). EF filters can also reduce chlorine from water, but may use activated carbon treatment, ion exchange technology, or a combination of these methods to remove impurities. Although these units may not produce as clear or odorless water as RO units, they are usually less expensive than comparable RO systems.
4. Distillers. Good for producing pure distilled water, but does not reduce heavy metals, chemicals, or bacteria like an under-sink water filter would. Distillation is more of a purification process, not an oxidation or chemical reduction process.
5. Ultraviolet light (UV). UV water filters are often used in conjunction with other types of under-sink units to kill bacteria in the filtered tap water. They are known largely for their ability to remove algae and parasites from filtered water, but they may also reduce chlorine and improve the taste of tap water.
6. Iron removal filters. A good under-sink filter can remove up to 70 percent of the iron in filtered water, but these units are not effective for removing fluoride or other heavy metals. 

Under sink systems may be more convenient because they can be moved from sink to sink, but countertop water filters may be less expensive, and the filters are easier to replace. 

If you have basic plumbing skills and know how to shut off the main water supply in your home, you may be able to install an under-sink water filter yourself. Otherwise, ask a plumber or find out if installation costs are included in the price of the system. 

Most brands recommend that their filters be replaced at least once every six months or after about 500 gallons of filtered water have been used. 

Yes, replacement filters vary in cost and can be purchased at a home improvement store. For instance, a filter from the Big Berkey system costs about $50 while a replacement for a basic faucet-mounted filter may only cost $25. 

Yes, these filters are typically easy to install with no tools required. However, once they are attached, you cannot move them from sink to sink like some under-sink filters can be moved. For example, you might have one filter for your kitchen sink and another filter installed on the bathroom basin. 

Solid carbon block filters are made from granulated active carbon, which is molded while in a highly compacted state, producing micro-pores so small that they cannot permit the passage of contaminants. They are the most effective filtration systems for providing safe drinking water. 

Carbon block filters are designed to remove impurities at the molecular level while solid carbon filters will absorb other chemicals that affect taste, color, or odor. Carbon blocks can also reduce heavy metal contaminants like lead and mercury. 

Reverse osmosis (RO) systems force water through a special membrane which acts like a filter trapping dissolved particles, bacteria and viruses while passing on the clean water to the faucet. RO filters are good for treating large quantities of impure or contaminated water, but they also waste more water than other types of filters. 

RO systems can be installed under the sink or near to where you need them like on the countertop, and they may come with a storage tank for easier dispensing of filtered water. Systems that are installed under the sink may contain between one and four filters to remove different contaminants like arsenic, fluoride, lead, or chlorine. RO systems will normally require regular maintenance.