Water Filtration Explained: From the Basics to Choosing the Right System

Q: What is the difference between GAC and CTO carbon filters?

GAC (granular activated carbon) provides higher flow and excellent taste and odour improvement. CTO (carbon block) offers finer filtration and longer contact time, making it ideal for drinking water polishing.

Q: What micron sediment filter should I use?

For municipal water, a 5 micron sediment filter is a good all-round choice. For borehole or tank water with heavier sediment, 10 to 20 micron filters last longer and maintain better flow.

Q: Do I need a sediment filter before carbon or RO filtration?

Yes. Sediment filtration protects carbon filters and RO systems from clogging, improving performance and extending system lifespan.

January 26, 2026

Clean water is essential for drinking, cooking, bathing, and protecting your home’s plumbing. But with so many filtration options available, choosing the right water filter can feel overwhelming.

This guide breaks water filtration down into simple, practical steps - from understanding the basics, to choosing the right system, and knowing when it’s time to replace your filters.

1) Why Water Filtration Matters

Even treated municipal water can contain sediment, chlorine, unpleasant tastes/odours, and in some cases bacteria (especially with borehole or tank water).

Better taste and smell (less chlorine and chemical odour)
Protects appliances and plumbing (less sediment and scale)
Cleaner drinking water with the right system
Extends lifespan of geysers, pumps, taps and filters

2) The Basic Stages of Water Filtration

Most effective filtration uses a staged approach. Each stage targets different contaminants.

Stage 1: Sediment Filtration (Always start here)

Sediment filters remove physical particles and protect your system from clogging.

Sand
Rust
Silt
Scale
Visible particles

Shop now: Sediment filter cartridges (Red Rhino) • Woven sediment cartridges (Red Rhino) • Sediment filter cartridges (WPE) • Woven sediment cartridges (WPE)

Stage 2: Carbon Filtration (Taste, odour & chemicals)

Carbon filters focus on improving taste and reducing chlorine and chemical odours.

Chlorine taste and smell
Common chemical odours
Some organic compounds

Two common carbon types:

GAC (Granular Activated Carbon) – higher flow, great taste improvement
CTO (Carbon Block) – finer filtration, better “polishing”, typically lower flow

Shop now: GAC carbon filter cartridges (Red Rhino) • CTO (carbon block) cartridges (Red Rhino) • GAC carbon filter cartridges (WPE) • CTO (carbon block) cartridges (WPE)

Stage 3: Advanced Filtration (Optional, depends on your water)

Reverse Osmosis (RO) – removes dissolved salts, metals and many contaminants
Ultra Filtration (UF) – reduces bacteria and microplastics with little/no water waste
UV Sterilisation – reduces bacteria using ultraviolet light (best after pre-filtration)

3) Micron Ratings (Made Simple)

A micron is a measurement of particle size. The smaller the micron number, the finer the filtration.

Micron Rating	Best For
1 Micron	Fine filtration, clearer drinking water (may clog faster)
5 Micron	General household use (best all-round choice)
10 Micron	Coarse sediment / pre-filter before carbon
20 Micron	Heavy sediment / first-stage filtration for borehole or tank water

Tip: Lower micron = finer filtration but faster clogging. Higher micron = better flow and longer filter life.

Explore systems: Under-counter RO & UF systems • UV steriliser (55W)

4) Choosing the Right Sediment Filter Type

Spun Polypropylene (PP)

Standard sediment filtration
Affordable and effective
Best for municipal water or light sediment

Woven Polypropylene

Higher dirt-holding capacity
Lasts longer where water is dirtier
Great for borehole or tank water

Grooved Polypropylene

Designed for heavy sediment loads
Progressive filtration extends lifespan
Ideal as a first stage for very dirty water

5) Which Filtration System Should You Choose?

For Municipal Water

Sediment: 5 Micron spun PP
Carbon: GAC or CTO

Optional: add a tap filter or under-counter system for drinking water.

Recommended setup: 5 micron sediment cartridge + GAC carbon (or CTO carbon block)

For Borehole or Tank Water

Sediment: 10-20 Micron (woven or grooved)
Carbon: GAC +/or CTO
Optional: UV steriliser (recommended when microbial risk is possible)

Recommended setup: 10–20 micron woven sediment cartridge + carbon filtration (optional: UV steriliser)

For Drinking Water Only (Kitchen tap)

Under-counter RO or UF system (best result for drinking water)
Or a tap-mounted / countertop filter for a simpler setup

Options: Under-counter RO/UF systems for best results, or tap-mounted filters / countertop filters for simpler setups.

For Whole-House Filtration

Multi-stage system (sediment + carbon)
Big Blue housings for higher flow and longer filter life
Optional UV where bacterial contamination is a concern

Whole-house options: Big Blue 20” whole-house systems • filter housings (Red Rhino) • filter housings (WPE) • Stainless steel systems • mounting brackets (Red Rhino) • mounting brackets (WPE)

6) How to Know When to Change Your Filters

Replacing filters on time is critical for performance and water quality.

Typical Replacement Guidelines

Filter Type	Typical Lifespan
Sediment filters	3-6 months
Carbon filters (GAC / CTO)	6-12 months
RO membranes	18-36 months
UF membranes	12-24 months
UV lamps	12 months

Signs Your Filter Needs Replacing

Noticeably reduced water flow
Bad taste or odour returns
Visible discolouration of the filter
Pressure drop in the system

Important: A clogged filter doesn’t just reduce flow - it can reduce filtration performance too. If in doubt, replace it.

Need replacements? Sediment cartridges (Red Rhino) • Sediment cartridges (WPE) • GAC carbon (Red Rhino) • GAC carbon (WPE) • CTO carbon block (Red Rhino) • CTO carbon block (WPE) • RO/UF replacement filters (Red Rhino)

7) Common Mistakes to Avoid

Skipping sediment filtration before carbon or RO
Choosing ultra-fine filters where flow is critical
Leaving filters unchanged for too long
Using the wrong housing size for the cartridge
Treating filtration as “set and forget”

8) Final Thoughts: Build a System That Matches Your Water

There is no one-size-fits-all filter. The best system matches your water source, balances flow and filtration quality, and is easy to maintain.

If you’re unsure, start with the basics:

Sediment → Carbon → Upgrade if needed

Need Help Choosing?

If you’d like help selecting the right filters for your home, borehole, or whole-house setup, contact us - we’ll guide you to the correct option based on your water source and goals.

Frequently Asked Questions

What is the difference between GAC and CTO carbon filters?

GAC (granular activated carbon) usually provides higher flow and excellent taste and odour improvement. CTO (carbon block) offers finer filtration and longer contact time, making it ideal for drinking water “polishing”.

What micron sediment filter should I use?

For municipal water, 5 micron is a good all-round choice. For borehole or tank water with heavier sediment, 10–20 micron often lasts longer and maintains better flow.

How often should water filters be replaced?

Sediment filters typically last 3–6 months, carbon filters 6–12 months, RO membranes 18–36 months, UF membranes 12–24 months, and UV lamps should be replaced annually.

How do I know when a filter needs replacing?

Signs include reduced water flow, pressure drop, bad taste or odour returning, or visible discolouration of the cartridge.

Do I need a sediment filter before carbon or RO filtration?

Yes. Sediment filtration protects carbon filters and RO/UF systems from clogging, improving performance and extending lifespan.