Setting Up a Water Filtration System: What Plumbers Need to Know

Water filtration is one of the fastest-growing areas of residential and light commercial plumbing in Australia. With increasing consumer awareness around water quality — and more builders and homeowners specifying filtration at the point of sale — licensed plumbers are being called on to install and commission these systems more than ever.

This guide covers everything you need to know: system types, correct installation procedure, compliance considerations, and the components you'll need on-hand. If you're looking to stock up, our filtration range includes connection kits, filter housings, and fittings at trade prices.

Types of Water Filtration Systems

Before you quote or order materials, it's worth understanding what's being installed. The four most common systems you'll encounter on residential jobs are:

1. Under-Sink Filters (Point of Use)

The most common domestic filtration job. These typically use one, two, or three-stage cartridge housings mounted under the kitchen sink, with a dedicated drinking water tap. Installation is straightforward but attention to detail matters — incorrect connections are the most common callback cause.

2. Whole-House Filters (Point of Entry)

Installed on the main supply line before the hot water unit, these filter all water entering the property. They require correct isolation valves upstream and downstream, and a bypass arrangement is best practice for ongoing maintenance access.

3. Reverse Osmosis (RO) Systems

Multi-stage systems that include a storage tank and waste water line to drain. RO systems require a feed water line, a drain connection, a pressure-feed storage tank, and a separate tap. These jobs take longer and the commissioning steps are more involved — but the margin is better.

4. Commercial & Inline Systems

Found in cafés, restaurants, and office buildings — often fed off a dedicated cold water line to appliances. These use higher-capacity housings, require a TP valve in some configurations, and may have specific manufacturer commissioning requirements.

What You'll Need: Components Checklist

Most filtration jobs can be covered with a fairly consistent parts list. Having the right stock in the van means fewer delays. Here's a standard checklist for a single under-sink install — most of these are stocked in our filtration range:

• Filter housing + cartridge(s) — matched to the water quality requirements and flow rate
• Filtration connection kit — fittings, tubing, and feed water adapter in one pack
• Flexible hoses — for the dedicated drinking water tap connection
• Mini stop / isolation valve — a service valve on the feed line is non-negotiable
• Brassware fittings — compression or push-fit depending on the setup
• Drinking water tap — 3/8" BSP thread is standard
• PTFE tape and thread sealant
• Drain saddle valve (for RO systems only)

Step-by-Step: Under-Sink Filtration Installation

This is the most common job type. Here's the correct procedure:

Step 1 — Isolate and Depressurise

Turn off the cold water supply under the sink (or at the main if there's no service valve). Open the cold tap to depressurise the line. This is obvious, but skipping it is how accidents happen.

Step 2 — Install the Feed Water Tee

Fit a tee and mini stop valve on the cold supply line upstream of the existing stop valve. Use a mini stop valve with a 3/8" compression outlet — this gives you a dedicated, serviceable feed point.

Step 3 — Mount the Filter Housing

Mount the housing to the cabinet wall or base — ensure it's accessible for filter changes (minimum 150mm clearance below for a filter wrench). Note the IN and OUT markings on the housing before connecting — reversing flow direction is a very common mistake on first-time installs.

Step 4 — Connect the Tubing

Run 3/8" polyethylene tube from the feed valve to the filter IN port, and from the OUT port to the drinking water tap location. Keep runs neat and avoid sharp bends that can kink the tube over time.

Step 5 — Install the Drinking Water Tap

Most kitchen benchtops have a pre-drilled hole for a drinking water tap; if not, you'll need to drill one (check for any under-bench obstacles first). Use PTFE on the tap shank threads and hand-tighten the locking nut — overtightening will crack the tap body.

Step 6 — Flush and Commission

Before handover, flush the system for the manufacturer-specified time (typically 5–15 minutes for carbon block filters). This removes carbon fines and saturates the media. Check all connections under pressure, and confirm flow rate at the tap is acceptable.

Whole-House Filter Installation: Key Differences

Point-of-entry installs follow the same basic principles but require more planning:

• Bypass arrangement: Always install a bypass loop with isolation valves on either side of the housing. This lets the homeowner isolate the filter for cartridge changes without interrupting supply to the whole property.
• Flow rate: Whole-house filters need to be sized for the property's peak demand. A single cartridge housing may restrict flow on larger homes — twin housings in parallel are often the right spec.
• Location: Install after the meter but before any internal branches. Protect from freezing if the install is in an exposed area (unlikely in most of Australia, but relevant in alpine regions).
• Valves: Use quality ball valves for the isolation points — not gate valves. Ball valves give a clear open/shut indication and seal more reliably long-term.

Common Mistakes to Avoid

Point-of-entry installs follow the same basic principles but require more planning:

• Reversed flow direction: Always double-check IN/OUT on the housing before connecting. Backflow through a carbon filter ruins the media.
• Skipping the service valve: A filter without an upstream isolation valve means a full shutdown to change the cartridge — homeowners hate this.
• Incorrect thread engagement: Filter housings use standard BSP threads. Don't cross-thread by hand-tightening on an angle.
• Not flushing: Carbon fines in the first few litres of water look terrible and erode customer confidence. Always flush before handover.
• Using non-WaterMark fittings: Cheap fittings sourced outside trade channels often lack WaterMark certification. Only use certified products.

Stock the Right Parts Before You Go

Most filtration callbacks come down to one thing: missing parts on the day. A well-stocked van means you can complete the job in a single visit. Beyond Plumbing Supplies stocks everything you need — from connection kits and flexible hoses to brassware fittings and isolation valves — all at trade prices, with next-day delivery Australia-wide.

Check out our Plumbers Kits for bundled essentials, or register free to unlock trade pricing across our full catalogue.

FAQs: Water Filtration for Plumbers

Do I need a permit to install a water filter in Australia?

It depends on your state and the scope of work. In most states, any work connecting to the mains supply requires a licensed plumber. A permit may be required depending on your local regulations — check with your state regulator if unsure.

Does a water filter need to be WaterMark certified?

Yes. Any plumbing product connected to a drinking water supply in Australia must carry WaterMark certification. This includes filter housings, fittings, and connection hardware. Always verify the WaterMark licence number before installation.

How often should a water filter cartridge be replaced?

Most residential cartridges are rated for 6–12 months or a specified volume (e.g., 5,000–10,000 litres), whichever comes first. Advise your customer of the replacement schedule at handover — it's a good opportunity to offer a service agreement.

Can a homeowner change their own filter cartridge?

Generally yes — filter cartridge replacement in a correctly installed system (with a service valve on the feed line) is not licensed plumbing work. Advise the homeowner to turn off the feed valve, relieve pressure through the tap, and follow the manufacturer's cartridge change procedure.

The Bottom Line

Water filtration installs are clean, fast jobs with a strong margin when you're set up correctly. The keys are: correct component selection, a service valve on the feed line, WaterMark-certified products, and a proper flush before handover. Get those four things right and you'll never have a callback.

Need to restock before your next filtration job? Browse our full filtration range at Beyond Plumbing Supplies — trade pricing, next-day delivery, backed by 60+ years of combined experience.