This applies to water filters that are mounted under the kitchen sink but not to reverse osmosis units under the sink. In a separate section, reverse osmosis will be described.
Filters, unlike reverse osmosis filters, process water on-demand and don’t require a storage tank. Water is not used. Each drop of water that is filtered out by a water filter is considered usable water.
Above is the traditional undersink filter. It draws its water from point A through a flexible tube. It then sends the water through a flexible tube to the water filter (B). It then leaves the filter through a flexible tube and is delivered by the filter’s special faucet (C) which is mounted on top of each sink.
The system operates under constant pressure. When the faucet is opened at the sink, water flows through the filter to the faucet.
Only water from the faucet can be filtered. The filter does not affect the sink’s normal cold or hot water functions.
Simple Undersink filters
The delivery system for the filter shown above is different. This arrangement allows the cold water supply to the sink to be diverted through the filter, and the filtered water to be dispensed via the regular cold water faucet. Hot water is not filtered.
With the introduction of flexible copper under-sink pipes, it is more practical to use the simple version without a separate ledge faucet. Installation of simple under sink units is easy and affordable with flexible delivery pipes.
| Conventional | Simple |
| Higher prices. It requires its own faucet. | Less expensive. Additional faucet not required. |
| For faucet installation, a hole must be made in the sink. | Additional faucets are not required. |
| Because only drinking water and cooking water are filtered, filter cartridges last for longer. | Because all cold water has to be filtered, it is more common to replace cartridges. |
| Reduced flow rates can lead to higher quality water. | Some filtration tasks are less feasible if the flow rate is higher. For example, fluoride and bacteria reduction. |
| It can be installed on both all-copper and flexible piping. | It can be installed on any type of under sink pipe, but it is much simpler to use flexible connectors. |
| Because of the lower flow rate, there is more choice in models. | Use only full-sized filters that have 3/8″ ports or greater |
Modern filter technology has allowed under sink filters that can perform tasks previously only possible with reverse osmosis to be created. Multiple filters can be used under sink space to achieve different objectives.
Most under sink filters have activated carbon filtration. This is usually done in the form of high-performance carbon block filters. Every under sink filter should contain at least one quality activated carbon filter. A good rule of thumb for choosing an under sink filter: “The more carbon, the better.”
This post was written by a water treatment expert at Pure Blue H2O. At Pure Blue H2O we are the providers of the best ro filter replacement! We know that the best product comes from the best materials. They offer whole home water solutions such as reverse osmosis systems, shower head filtration, filter replacements, and a variety of similar products. Their focus is to provide Americans with safe and clean water throughout the home.
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