How Do I Install an Under-Sink Water Filter?

Before You Begin

Crystal Quest under-sink water filtration systems are designed to deliver high-quality filtered drinking water at the point of use. These systems can be configured with a variety of filtration media, including carbon, SMART, fluoride, arsenic, nitrate, ceramic, or multi-stage combinations,depending on your specific water quality needs.

This guide provides a general installation overview to help you understand the components, connection points, and sequence involved in installing a Crystal Quest under-sink system.

Important Installation Notice
This information is provided for educational and reference purposes only. Installation methods, plumbing configurations, and code requirements vary by location. Crystal Quest recommends that under-sink filtration systems be installed by a qualified, licensed plumber in accordance with the official Installation & Operation Guide and all applicable local plumbing codes. Installation by anyone other than a licensed plumber may void the system warranty.

Tools and Materials Required

Actual tools may vary depending on your plumbing configuration and installation method.

Required tools include:

Adjustable wrench
Phillips and flathead screwdrivers
Drill and appropriate bits (only if installing a dedicated faucet)
PTFE (Teflon) thread seal tape
Bucket and towels
Safety glasses

System Components

A Crystal Quest under-sink filtration system includes:

Filter housing(s) with installed cartridge(s)
Mounting bracket and hardware
T-valve feed adapter (standard)
Optional saddle valve
Tubing and quick-connect or compression fittings
Dedicated filtered water faucet (if applicable)

Component configuration may vary by model.

Step 1: Shut Off the Cold Water Supply

Locate the cold water shut-off valve beneath the sink and turn it clockwise until fully closed. Open the cold water faucet to relieve pressure and confirm the water is off. Place a bucket and towels beneath the work area to catch any residual water.

Step 2: Choose Your Installation Configuration

Crystal Quest under-sink systems support two primary configurations.

Dedicated Faucet Installation (Most Common)

Filtered water is delivered through a separate dedicated spout.

Benefits include:

Longer filter life (only drinking water is filtered)
Clear identification of filtered vs. unfiltered water
No impact on main faucet flow

Inline Installation

Filtered water is delivered through the existing cold water faucet.

This option may be preferred when:

Drilling a faucet hole is not possible
A streamlined appearance is desired
All cold water at the sink should be filtered

Step 3: Connect to the Cold Water Supply

T-Valve Installation (Standard)

Crystal Quest systems include a T-valve, designed for installation on flexible supply lines.

General connection sequence:

Shut off cold water
Disconnect the existing cold-water supply line
Install the T-valve inline using thread seal tape
Connect filter supply tubing to the T-valve outlet
Slowly restore water and check for leaks

Pressure Note:
Supply pressure should not exceed 60 PSI. A pressure regulator is recommended if household pressure is higher to reduce stress on fittings and housings.

Saddle Valve Installation (Optional)

Saddle valves may be used where permitted by local plumbing codes and are typically installed on rigid copper piping.

Important considerations:

Not recommended for flexible tubing
Prohibited in some jurisdictions
More prone to leaks over time

Always verify local code compliance before using a saddle valve.

Step 4: Mount the Filter Housing

The filter housing may be wall-mounted or placed securely on the cabinet floor.

Best practices:

Confirm correct inlet and outlet orientation
Leave adequate clearance below housings for cartridge replacement
Secure housings to prevent movement or vibration

Step 5: Install the Dedicated Faucet (If Applicable)

If no existing sink hole is available:

Stainless steel sinks may be drilled with proper tools
Porcelain, ceramic, granite, or stone surfaces should be drilled by a professional to prevent cracking

Install faucet hardware according to the product instructions, ensuring all washers and fittings are properly seated.

Step 6: Connect the Tubing

Cut tubing cleanly and square
Insert tubing fully into quick-connect fittings
Install locking clips where provided
Route tubing away from sharp edges, heat sources, or moving cabinet parts

Improper tubing insertion is a common cause of leaks.

Step 7: Flush and Test the System

Before using filtered water:

Ensure cartridges are oriented properly in sumps with O-rings seated correctly
Slowly restore the cold water supply
Inspect all connections for leaks
Open the filtered water faucet
Flush the system for 5-10 minutes

Initial cloudiness or gray water is normal and caused by harmless carbon fines. Continue flushing until water runs clear.

Maintenance and Filter Replacement

Filter replacement intervals vary by cartridge type and water quality.

Common indicators for replacement:

Reduced flow rate
Return of taste or odor
Reaching the recommended service interval

Use only Crystal Quest replacement cartridges to maintain system performance and warranty coverage.

Need Assistance?

Crystal Quest’s technical support team is available to assist with system selection, installation guidance, and maintenance questions.

If you have questions about your specific under-sink system or installation requirements, contact our support team for personalized assistance.