Unlike some portable water filters, the faucet and which have a direct connection, the under the counter water filters are directly attached to the plumbing under the counter. An under the counter water filter remains out of sight and does not have to be turned off or on, even as it provides a constant supply of clean water.

There is some more installation work required for under the counter water filters, as against that required for the water filters which can be attached to taps. Although a separate drain line is not required, a feed line has to be provided for connecting under the counter water filter with the main water tap and the cold water tap. The under the counter water filter system generally has all the relevant instructions as well as all parts required for installation, supplied along with it.

A plumber may be called upon to install an under the counter water filter or the filter system may be installed by home owners within a time period that generally does not exceed an hour. On account of the transparent operation of the under the counter water filter and its being unobtrusive, once it has been installed, besides the counter space that is saved as a result, it is preferred by many people.

Like other water filtration systems, replacement of the cartridge has to be carried out for an under the counter water filter system, at regular intervals. The procedure for cartridge replacement is quite simple. Once the fitting under the sink of the counter water filter system has been done, the tasks that are required to be performed are quite simple. After unscrewing the cover, the new cartridge has to be installed, after removing the one installed earlier. Then, the replacement of the cover is in order.

By taking a look under the sink, the pipe through which cold water is being fed to the tap has to be identified, so that an under the counter water filter can be installed. If one is not able to immediately locate the pipe that one is looking for, the process of identification can be helped by a minute or two of the hot tap being kept running. The pipes can then be distinctly identified as the cold and the warm one by touching each of them.

The saddle valve clamping device then has to be installed on a section of the pipe, after ensuring that there are no obstructions or corrosion. The device that has tubing attached to it and resembles a small clamp is the saddle valve. Depending upon the pipe's diameter, the appropriate side has to be selected while setting the clamp's small mounting block on to the pipe, followed by the tightening of the nut at the base, after fitting the clamp over the mounting block and the pipe.

A bucket or another receptacle has then to be used to place the tube's red end in. The T-bar handle then has to be turned fully in the clockwise direction, so as to pierce the copper pipe. Utilizing the screws that are supplied along with the system, at a location that is suitable, the cabinet has to be mounted with the filter's housing bracket. After that, the housing of the filter has to be installed with its cartridge. The cartridge may have to be screwed in to the housing or simply be placed in the suitable fashion. The bracket then has to be mounted with the re-assembled housing of the filter.

The water flows to the tap, through the filter housing, from the red tube, after the T-bar of the saddle valve is turned anti-clockwise. The under the counter water filter's housing's output side is connected to the blue tube from the tap. Installation of the tap and the tubing related to it precedes that, along with the connection of the red tube in the bucket with the input side of the filter housing. The drinking water tap or the faucet for the under the counter water filter system is installed, after drilling a hole in the sink or worktop, at a location that is appropriate.