How to Install An Under The Sink Water Filter | 10-Step Guide

Written by Tim Rhodes Last Updated: Sep 4, 2024

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‘How to install under sink water filter’ is a question that will cross your mind a couple of times, if you’re considering purchasing this type of filter and you’re big on DIYs.

If you’re bothered with how the water from the faucet smells and tastes like, then a water treatment solution like an under sink water filter is a good choice to properly cleanse the water coming out from the faucet.

There are few considerations for providing safe water for consumers but what matters, is its safety, costs, ease of maintenance, availability, and accessibility.

It is a popular method for water treatment, to provide families and homeowners, the desired quality of water for their loved ones, right next to their regular kitchen faucet.

Other choices include Water Pitcher or countertop filter, but the under the sink is highly selected by most populations, due to its ease of installation, minimal maintenance required, lesser cost of replacement, and efficiency in filtering out of the cold water sources, to provide the desired safe drinking water.

It is a perfect choice for most people having congested time and never having the spare energy, for most scenarios.

Asides its benefits and accessibility, its installation is not a problem since the steps on how to install under sink water filter will be explained thoroughly.

Step 1: Provide a Place For The Faucet 

In most cases, a newly installed faucet is dedicated, to safe drinking water.

Skip to Step 3 if what you are looking for is an installation guide, for the existing faucet, where the under sink water filter is to be attached. 

Drill a hole from the sink, where the dedicated safe drinking water faucet is to be mounted.

Oftentimes, other sinks consist of a pre-existing hole right beside the regular faucet, dedicated to other faucets, to be installed in the future.

So observe if you have one, to avoid this step.

If a new hole needs to be done, grab the newly bought faucet and decide on which drill bit is to be used.

Normally a 1 ¼ inch drill will do.

In deciding where to install the new faucet, you don’t want it to be located away from the existing one since the water source will be used, and installing them right next to the existing faucet, will avoid the more complicated procedure of installing the filter later on.

Usually, it resides right next to the existing regular faucet.

Make sure that it is comfortable and convenient enough, to feed a glass of safe drinking water. 

Consider The Materials Of The Sink:

Since drilling the sink is not common to everyone, it is a bit difficult, especially where inappropriate drilling techniques and drill bit materials are used.

The worst-case scenario will bring a broken drill bit, while installation and injury might occur.

If you are not confident enough in handling these tools, have someone help you in doing this task.

This step, on how to consider materials of the sink to be drilled on, will help you understand a simpler drilling technique.

Having a ceramic sink involves a drilling technique called the “Knock out method” or “Diamond Tipped Hole Saw”.

However, remember to use an appropriate drill bit size and material.

While having a stainless steel sink is a lot easier, simply preventing the sink from being overheated, by applying lubricant, is a must.

You have to use a standard cartridge tipped blade, by starting from a smaller drill bit of ¼ inch and scaling to a larger bit size, until an appropriate hole is drilled.

Step 2: Run The Water Line 

Upon drilling the hole, allow the waterline through the sink and mount the faucet appropriately using the nut supplied.

Make sure that the faucet is securely attached to the sink.

In most cases, securing the sink involves washer and nuts to be tightly attached, underneath the sink.

You can use a Caulk as adhesive, in installing the gasket or trim, but always remember to wipe away excess application.

Pull down the line under the sink to keep it straight.

Refrain the line from any dust particle, to keep it clean for drinking purposes.

If you think any dust entered the line, avoid cleaning them inside, especially if no tools are appropriate.

There will be a couple of cycles, where water runs to avoid contamination, so any unnecessary polluting particles will be washed off, before having the desired safe drinking water. 

You might expect to have the line organized and mounted on the wall, however, this is not recommended, since the line handles water.

Once these lines are attached to walls using adhesive or any mounting techniques, there’s a tendency for the lines to be bent.

This creates pressure along the bent edges, which will result in maintenance for leaks or early replacement of lines.

Step 3:Shut Off The Cold-Water Supply

Installing the under-sink water filter requires safety precautions, to prevent further damages to other items involved in the installation.

Determine the source where the water is being supplied.

This is where being familiar with the kitchen, particularly the arrangement of the sink and how the different hardware installed under the sink comes in.

It might get a bit messy, depending on how often the sink is cleaned or how often it is accessed by anyone.

Nevertheless, what is important, is locating the important items such as the source valve; which comprises cold-water and hot-water supply, and its corresponding line where the water flows.

What should be shut off is the cold-water supply, simply because this is a source that is to be cleansed by the filter.

As a standard, it is the usual practice not to filter hot water, as this destroys the filter itself.

Identify and turn off the cold-water shutoff valve.

Make sure that the knob is properly turned off, else it could result in leaks, as the tubing is removed from the valve.

Further procedures are presented, if the cold water shut off valve is not properly turned off.

If you are having trouble turning off the valve, due to rust that permits them from being turned off, use appropriate tools such as pliers to help you. 

Identifying Cold-Water

If you have any trouble identifying which one is the cold-water valve, try turning on the hot water supply, which will make it easy to identify the different lines.

The line with the higher temperature is where the hot-water shutoff valve is connected.

Thus, we can conclude that the other line is for cold water.

Step 4: Drain The Cold Water 

Turn on the faucet, to properly drain the cold water residing in the line.

This makes sure, that there will be no leaks while installing the actual filter.

When in doubt if the valve was properly turned off, turning on the faucet determines it.

If the water continuously runs without draining, check to turn off the cold water shut off valve.

Use the necessary tools, when turning the knobs feels difficult. 

Step 5: Disconnect The Tubing Line

When the water is properly drained by turning the faucet on, remove the tubing line from the shut-off valve, by loosening the nuts connecting both items.

Use a wrench to properly adjust the nuts and slowly detach the tubing line.

Avoid any breakage of material from the valve and the line, since both of these are still to be used, in the installation process.

Commonly, you might experience water spilling from the tubing, upon detaching from the valve.

But since you have turned on the faucet and properly drained the water from the line, spillage is very minimal.

Wipe Spilled Water Under The Sink

It is best practice, to wipe off the spilled water when the tubing line is disconnected.

This keeps the valves, line, and the entire under sink best clean and avoids awful smell, when the spillage lasts longer, without being wiped off.

It is also a way to have the materials preserved, which prevents further maintenance.

Use a rag or any cloth in wiping off the excess spilled water, over the sink.

Do another cycle when needed to dry them off.

Step 6: Provide a Place For The Filter

Decide where the filter is to be mounted under the sink.

It is important, that there is enough room or space below the filter.

The purpose of this is to easily detach the canister and easily change the cartridges, for maintenance purposes.

This allows you to have access to the filter when needed.

How the filter should be mounted under the sink, is totally up to individual preferences, but a few considerations might help you, on where to install them.

It is necessary to have the filter mounted, close to the cold water line, to make sure that the length of water pipes provided by the manufacturer is sufficient.

Insufficient length of water line will cause installation problems, that’s why the closer the filter is to its source, the better. 

Oftentimes, mounting the filter involves only a mounting bracket or plates and screws, to attach them to your desired location.

Mark the location by partly screwing them together.

When screws are highway mounted, this gives enough manner of installation later on.

Remember that the screws will completely be mounted later on, while the filter is permanently hung in place. 

Step 7: Assemble The Filter

Since the location for the filter is already marked, temporarily remove them from the place.

Check the newly bought filter, if it consists of the type of material, its supply lines have.

Most often, it has plastic tubing lines that come within. 

Connect the water to the brass fittings attached to the filter.

Use a more reliable seal like a Teflon tape, to avoid leaks and malfunctions of the item.

This section, where the brass fittings and lines are connected are often observed upon installation because this is where leaks are found.

A common cause of this is improper installation, by not using the appropriate tape.

Tighten the fitting slowly by using a wrench, and avoid tightening the wrench quickly, as this causes the fitting to be destroyed easily.

Never overly tighten the fitting, as this causes early maintenance and replacement of the fitting. 

Use Flexible Stainless-Steel Lines

It is highly recommended to purchase and use flexible stainless-steel lines, or so-called “flex lines”. 

It has the property of being a more sturdy material, than the usual plastic inside the box and comes in different lengths.

As mentioned in the earlier step, shorter water lines cause problems, when insufficient length cannot connect the valves or source to the filter.

Since there are sufficient lengths of this type of material, you can conveniently install the filter, on any of your preferred locations.

However, buying more lengths of these flex lines is expensive, so the more precise the length, the better.

Step 8: Hang The Filter

Choose a preferred location to install the filter, while making screw marks under the sink.

Mount the filter to the desired location, by fixing the screws fully.

It has to be the ones that are provided by the manufacturer, inside the box.

If you feel a more reliable screw should be used, provide one that uses a stronger material.

This makes the installation easier, as the screws are attached to walls permanently, with lesser effort.

Use appropriate screwdrivers, to prevent the screws from being stripped.

Screwdrivers come in different sizes, however, if the exact size is not available, the size next to it is a more applicable screwdriver.

Gently fix the screws with a right angle and don’t use much force, as the screwdriver should do the job.

Make sure to secure the filter, by making the bracket sturdy enough to hold the filter.

Be sure to confirm, that the filter will hold on to the bracket attached to the walls, as it might get non-functional when it suddenly drops.

One thing to remember in this installation is, to prevent the filter from any physical damage, as this provides leaks along any joint.

Any physical impact on the surface of the filter could lead to permanent damage, of the entire unit, as it will likely result in leaks.

Step 9: Connect The Lines

Connect the flex line that pertains to the “in” fitting, to the cold-water shutoff valve.

Connect the flex line that refers to the “out” fitting, to the faucet line.

Don’t be confused about how these lines are to be connected from and to the filter, as signs are shown, for ease of connection.

You might want to use appropriate tools in adjusting the fittings, as these joints are crucial to avoiding leaks.

The lines are not to be attached to walls, as an adhesive is used to protect itself from being bent, and from the pressure that concentrates at certain edges, causing early replacements and further maintenance.

Let the water run along the lines naturally, without any obstruction, for easy dispensing of the water from the faucet.

Step 10: Make a Test

This is probably the most pivotal part of the entire process.

Turn on the cold water valve and observe all connections made, if there are no leaks, then the filter is properly installed under the sink.

Once leaks are found, in any of the crucial joints where the ends of each line meet with the corresponding tubing, then turn off the cold-water shutoff valve, immediately.

Press the pressure-relief button, to securely pass out trapped air.

Turn on the faucet for a few rounds, to ensure that the cleansed water, is now quality safe drinking water. 

Make Multiple Cycles Of Turning On The Faucet

It is highly recommended, to make several tests of turning the faucets off and on.

This allows the line to be cleaned, as the water travels through it, with the filter functioning as expected.

Normally a few minutes of cycling test will be enough, to make the water reach the desired filtered state.

As the cycles are made, observe each joint again for leaks.

If you are confident that there are no leaks in any crucial part of the installed items, then proceed with your glass of water. 

Choosing The Right Under-Sink Water Filter

Different under sink water filters provide different advantages, however, they all serve the same purpose ultimately.

You can choose between several kinds but the following are most commonly used; Neo-Pure RO- 4300RX- DLX, Everpure ADC RV, Viqua DWS-UV, Neo-Pure K-NPQ1, Neo-Pure TL3, etc.

If you are a person who loves to camp with the RV in hand, having an Everpure ADV RV is a must.

It has a bacteriostat media that disinfects chemicals leaving no worries about any bacteria from the camping environment.

With its convenience of not gathering the garden hose adapter, requiring them to be connected outside the RV, this filter can be plumbed right under your sink with easy replacements of part and other materials.

With dealing with reverse osmosis technology where efficiency is sufficiently advantageous over the other types, the Neo-Pure RO- 4300RX- DLX filter is the one you should get.

It enhances the flavor of the filtered water right to your glass having that mineralized taste even when having tea and coffee.

All filters have the purpose of cleansing water for drinking.

A clear understanding of them all is necessary to assess and determine, which one suits you.

Final Thoughts

Installing the under-sink water filter is easy if, this installation procedure on how to install under sink water filter is followed.

This kind of filter offers reliability and the guarantee of easy maintenance of the different parts, having lesser costs of material replacement.

It is so compact, that it generally fits any kind of kitchen sink and it doesn’t require any technical knowledge and skill to understand how the system works.

Experience with different hardware and tools can come in handy for installation, however, a good read of the manual is necessary, for a successful installation.

Sometimes, it gets a bit messy depending on the kind of sink and kitchen you are working on, but in every under-sink water filter installation, the idea of how to handle them is the same.

Now that you have this newly installed under sink filter, you can enjoy this safe drinking water in the comfort of your home.

Feel free to leave your thoughts on this article, in the comments section below.