Learn About Water Filters Before You Buy

When you invest in a quality whole-house, underbench, or fridge water filter system, you expect clean, safe, and great-tasting water. While 12 months is often quoted as the baseline, replacement schedules depend on your system type, water usage, and time:

• Fridge Water Filters: Replace every 6 months or after approximately 1,100–1,500 litres (300–400 gallons). Stagnant water in fridge filters can lead to bacterial buildup if left longer.
• GAC Underbench / Under-Sink Systems: Replace every 6–12 months or after 2,000–7,500+ litres, depending on household size.
• Whole-House Systems: Replace sediment pre-filters every 3–6 months and main carbon cartridges every 6 months.

Staying proactive keeps your system running like new and prevents drops in tap pressure or water taste.

GAC with KDF Media Increases Lifespan

Standard GAC cartridges are rated for 6–12 months or 5,000–10,000 litres. Adding KDF (Kinetic Degradation Fluxion) extends lifespan significantly because:

1. Bacteriostatic Protection: KDF uses a copper-zinc redox process that prevents bacteria, algae, and fungi from breeding inside the filter.
2. Heavy Metal & Chlorine Load Reduction: KDF neutralizes chlorine and heavy metals before they reach the carbon bed, preventing premature clogging.

When Should You Replace Sooner?

Even before reaching the litre limit, replace the cartridge if:

• Time Expiration: The cartridge reaches its max time limit (2–3 years max to prevent structural degradation).
• Flow Drop: Water pressure at the tap slows significantly.
• Taste/Odour Return: Bad chlorine or chemical taste returns before the litre limit is hit.

1. Improved Taste and Odour

Filtration removes chlorine and naturally occurring minerals that cause unpleasant taste or smell.

2. Removal of Contaminants

While NZ water is well-regulated, contaminants can still enter the supply:

• Heavy Metals: Lead and copper from aging pipes.
• Microorganisms: Bacteria, viruses, and protozoa that municipal treatment may not fully remove.
• Chemicals: Pesticides, herbicides, and pharmaceuticals in trace amounts.

3. Protection Against Infrastructure Issues

Aging pipes can introduce contaminants through corrosion or leaks. Filtration adds a layer of protection.

4. Hard Water Treatment

In hard water areas, filters or softeners prevent scale buildup in pipes and appliances, extending their lifespan.

5. Health Concerns

For those with weakened immune systems or specific health conditions, filtering water offers additional protection.

6. Peace of Mind

Filtration provides reassurance that your water is as clean and safe as possible — especially important for families with children or elderly members.

Recommended Filtration Systems

• Whole House Filtration: Sediment and activated carbon filter at the point of entry to remove particles and chlorine.
• Point-of-Use Systems: For drinking and cooking, consider a reverse osmosis (RO) system for removing a wide range of chemical and biological contaminants.

Choosing the right filter isn't just about what it removes — it's also about maintaining strong water pressure throughout your home.

10" Big Blue Systems

Best for: small households and lower simultaneous water use

20" Big Blue Systems

Best for: family homes, multiple bathrooms, and higher flow demand

Why Flow Rate Matters

All filters create some restriction. If a system is undersized, you may notice lower shower pressure, slow bath filling, or reduced flow when multiple taps are running. That's why we recommend matching the filter size and type to your household demand — not just the contaminants you want removed.

Pressure Drop by Filter Type

• Radial Flow GAC — Lowest pressure drop. Best for high-flow applications or homes already struggling with low pressure.
• GAC / KDF — Moderate pressure drop. Generally efficient for standard household needs.
• Standard GAC — Higher pressure drop. Water travels end-to-end through the carbon bed.
• Carbon Block — Most restrictive. If you need carbon block, size up to 20".

Our Recommendation for NZ Homes

20" systems are the best all-round choice. They deliver better pressure, longer filter lifespan, and more consistent performance.

• Want maximum flow with minimal pressure drop? → Choose radial flow carbon or a larger filter housing.
• Want finer filtration? → Use carbon block, but size up to 20".

Heavy metals are metallic elements that can be toxic when present in elevated concentrations. Common heavy metals found in water include:

1. Lead (Pb) — Often from corroding pipes and old infrastructure.
2. Mercury (Hg) — Usually from industrial pollution and runoff.
3. Arsenic (As) — Can leach from natural deposits or industrial waste.
4. Cadmium (Cd) — Common in agricultural runoff and deteriorating galvanized pipes.
5. Chromium (Cr) — Often from industrial waste and natural mineral deposits.
6. Copper (Cu) — Excessive copper can come from corroding pipes.
7. Nickel (Ni) — Found due to industrial activities and plumbing corrosion.

These metals can accumulate in the body, causing kidney damage, neurological disorders, and developmental issues in children. Testing and proper filtration (reverse osmosis or activated carbon) are typically used to remove them.

Research: Heavy metal exposure could increase cardiovascular disease risk — Journal of the American College of Cardiology

Carbon Block Filters (CTO)

Our high-quality NSF-certified Matrikx carbon block filters effectively remove chlorine, improve taste and odour, reduce sediment, VOCs, disinfection byproducts (THMs), and some heavy metals like lead. Typical filtration rating: 5 microns.

A 1-micron CTO Plus carbon block filter captures smaller particles including fine sediment, rust, and some microorganisms like cysts (e.g., Giardia, Cryptosporidium).

KDF Media

KDF filters use a copper-zinc alloy to remove contaminants through redox reactions, safely reducing iron, chlorine, hydrogen sulphide, heavy metals, and inhibiting bacterial growth.

KDF 55 removes up to 98% of inorganic water-soluble heavy metals, controls microorganisms, and reduces lime scale. Benefits in summary:

Less bacteria • Less free chlorine • Less heavy metal content • Less scale buildup • Less filter maintenance

Granular Activated Carbon (GAC)

GAC effectively removes chlorine, chloramine, VOCs, pesticides, herbicides, THMs, and improves taste and odour. Note: GAC does not effectively remove microorganisms, nitrates, or dissolved minerals.

Choosing the Right Carbon Filter

• Carbon Block: Ideal for high-efficiency contaminant removal and improving taste/odour. Consistent filtration but potentially slower flow rates.
• KDF GAC: Suitable for removing heavy metals, preventing microbial growth, and allowing higher flow rates.

Reverse Osmosis (RO) — #1 Choice

RO filters remove 99.9% of all chemicals, heavy metals, viruses, microorganisms, herbicides, and pesticides. It is the top choice for the purest drinking water.

Activated Carbon with KDF (KDF-GAC)

Omnipure KDF-GAC inline filter cartridges provide better-tasting, safer drinking water with bacterial reduction. Reduction rates: View products

• Aluminium 97% • Chlorine 99% • Selenium 98% • Arsenic 96%
• Chromium 96% • Mercury 99% • Lead 85% • Copper 90%
• Iron 50–90% • Nitrate 75% • Cadmium 80% • Sulphur 99%
• TTHM 99% • Endrin 86% • Lindane 99% • Toxaphene 85%

Whole House Filtration

Install a multistage system (twin or triple) for maximum coverage:

• Sediment Filters: Capture particles from 50 microns down to 1 micron.
• Activated Carbon Filters: Remove chlorine, improve taste and odour.
• KDF Activated Carbon Filters: Remove chlorine, reduce heavy metals and bacterial buildup.
• UV Purification: Chemical-free disinfection that eliminates bacteria, viruses, and protozoa.

At NZ Pump and Water Filters we offer only certified, top-quality water filters across all our brands. There is no compromise on quality.

Each natural water source has unique filtration needs:

• Rainwater: Requires first-flush diverters and sediment filters to remove debris and pollutants, plus UV purification for safety.
• Well Water: May need water softening, iron, and manganese removal.
• Stream and River Water: Use a combination of sediment filtration, activated carbon, and UV purification.

Larger 20-inch filters generally provide:

• Higher capacity and flow rates — less pressure drop across the system.
• Longer lifespan with less maintenance — while they cost more initially, they offer better efficiency for whole-house and high-demand systems.

Regular filter replacement is essential for maintaining clean water. Even if it costs more upfront, it's still far more affordable than bottled water.

Removing fluoride from water requires specific filter media. The most effective methods are:

#1 Reverse Osmosis (RO): Removes up to 85–97% of fluoride alongside other heavy metals. One of the most effective ways to reduce fluoride at the tap.

#2 Water Distilling: Steam is condensed back into liquid, producing purified water with significantly reduced fluoride, minerals, heavy metals, and most contaminants.

#3 Activated Alumina (AA) Filters: NSF 61-certified granular activated alumina is designed to effectively remove fluoride and arsenic. Made from aluminum oxide, it has an exceptionally high surface area for fluoride adsorption. AA filters can reduce fluoride from ~2 ppm down to below 0.1 ppm.

pH Levels Impact Activated Alumina Performance

The optimal pH for activated alumina is 5.5–6.5. At this slightly acidic range, fluoride adsorption is maximised:

• At pH 7.5: Efficiency drops to approximately 30–50%.
• At optimal pH 5.5–6.5: Efficiency can reach 85% or higher.

Approximate Lifespan Guide

Based on a 10" x 4.5" AAL cartridge with 2.5–3 kg of media and average daily usage of 100 litres:

• At pH 7.5: Filter lasts up to ~45 days.
• At optimal pH 5.5–6.5: Filter lasts up to ~180 days.

• 10" Jumbo cartridges: approx. capacity of 15,000 litres.
• 20" Jumbo cartridges: approx. capacity of 30,000 litres.

Note: There is no definitive time frame or guaranteed lifespan for fluoride filters. Periodic water testing and replacement based on usage are recommended.

Best Activated Alumina Setup

An undersink dual water filtration system with a low-flow tap provides the best results, effectively removing up to 98% of fluoride when new. A second CTO 1-micron carbon block filter improves water quality and prevents taste issues.

For whole-house systems, maximise contact time with the filter media by keeping flow rates low (under 10 L/min per tap) for best fluoride reduction rates.