Under-Sink Water Filter Installation Guide | Australia

An under-sink water filter installation is usually much simpler than a whole-house installation because all of the equipment sits inside the kitchen cabinet and treats water for one drinking point. The exact process depends on whether you are installing a simple cartridge filter or a multi-stage reverse osmosis system.

For customers comparing RO options, the 5-stage reverse osmosis water filter system is the standard residential configuration, while the full reverse osmosis range covers other stage counts and treatment options.

What you need

Typical tools:

• Adjustable spanner
• Phillips-head screwdriver
• Bucket and old towel
• Drill and suitable hole saw if a new filtered-water tap hole is required
• Spirit level for mounting brackets where needed
• Tube cutter or sharp blade for clean, square tubing cuts

Typical fittings supplied with an under-sink system may include:

• Cold-water feed adaptor
• Push-fit tubing, commonly 1/4" or 3/8"
• Dedicated filtered-water tap
• Mounting bracket
• Shut-off or isolation fittings appropriate to the system

Check every fitting before starting. The exact connection depends on the plumbing already under the sink, so do not assume every kitchen uses the same thread or tube size.

Standard under-sink filter installation

1. Turn off the cold-water isolation valve and open the kitchen tap briefly to release pressure.
2. Place a bucket and towel under the connection before disconnecting any hose or fitting.
3. Install the cold-water feed adaptor supplied with the filter, following the product instructions.
4. Mount the filter housing or bracket somewhere accessible for future cartridge changes.
5. Cut push-fit tubing square and push it fully into each fitting. Tug gently to confirm it is locked in place.
6. Install the dedicated filtered-water tap through an existing hole or a correctly sized new opening where appropriate.
7. Connect the filter outlet to the drinking-water tap and check that tubing is not kinked or sharply bent.
8. Open the water supply slowly and inspect every connection for leaks.
9. Flush the cartridges for the volume specified by the product instructions before drinking the water.

Installing a reverse osmosis system

Reverse osmosis installation follows the same basic feed-water principle but adds several components. A typical 5-stage under-sink RO system includes sediment and carbon pre-filtration, the RO membrane, post-carbon polishing and a pressure storage tank.

Plan cabinet space before starting. The filter manifold and storage tank both need room, and future cartridge changes should not require removing the entire installation.

RO systems may also require a drain connection for reject water. Because drain and plumbing requirements vary by installation and jurisdiction, use the manufacturer's instructions and engage a licensed plumber where the work falls within regulated plumbing.

Choosing between a standard filter and RO

A standard under-sink water filter is usually the simpler choice when the goal is chlorine, taste, odour and sediment reduction at the kitchen tap.

A reverse osmosis system adds membrane filtration for much broader dissolved-contaminant reduction. The 5-stage RO system is a useful middle point for households wanting dedicated pre-treatment, the RO membrane and post-carbon polishing without adding an additional remineralisation stage.

When to call a plumber

Use a licensed plumber where the installation requires regulated plumbing work, where a drain connection needs professional installation, where existing plumbing is damaged or non-standard, or whenever you are not confident that the connection can be completed safely and compliantly.

If a fitting drips during testing, shut the water off before investigating. Push-fit leaks are commonly caused by tubing that is not fully inserted, is cut at an angle, or has a damaged end. Re-cut the tubing square where appropriate and replace damaged fittings rather than trying to compensate by over-tightening them.