Whole House Filter Flow Guide (Big Blue Systems)
Choosing the right filter isn’t just about what it removes — it’s also about maintaining strong water pressure throughout your home.
Below is a simple guide to what each filter type can comfortably handle in a typical household:
🔹 10" Big Blue Systems (Standard Homes / Lower Demand)
Filter Type Best For Comfortable Flow Rate Sediment (20–50µ, pleated) Dirt, rust, particles 30–50 L/min Radial Flow Carbon (GAC) Chlorine, taste, odour 30–40 L/min Standard Carbon (GAC/KDF) General chemical reduction 15–25 L/min Carbon Block (5–10µ) Finer filtration, better chlorine removal 8–15 L/min Carbon Block (1µ) Very fine filtration 5–10 L/min 👉 Best suited for: small households, lower simultaneous water use
🔹 20" Big Blue Systems (Family Homes / Higher Demand)
Filter Type Best For Comfortable Flow Rate Sediment (20–50µ, pleated) Dirt, rust, particles 60–90 L/min Radial Flow Carbon (GAC) Chlorine, taste, odour 50–70 L/min Standard Carbon (GAC/KDF) General chemical reduction 25–40 L/min Carbon Block (5–10µ) Finer filtration, better chlorine removal 15–25 L/min Carbon Block (1µ) Very fine filtration 10–20 L/min 👉 Best suited for: family homes, multiple bathrooms, 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
- Reduced flow when multiple taps are used
That’s why we recommend matching the filter size and type to your household demand, not just the contaminants.
Our Recommendation
For most New Zealand homes:
- 20" systems are the best all-round choice
- They provide better pressure, longer lifespan, and more consistent performance
Simple Rule of Thumb
- Want maximum flow & minimal pressure drop? → Go radial carbon or larger filters
- Want finer filtration? → Use carbon block, but size up to 20"
Need Help Choosing?
- Radial Flow GAC: Offers the lowest pressure drop. Because water flows from the outside of the cylinder to the center rather than through the entire length, it allows for very fast flow. This is the best choice for high-flow applications or homes already struggling with low pressure.
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GAC / KDF: This provides a moderate pressure drop. The mix of carbon and alloy adds some resistance, but it is generally efficient for standard household needs.
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Standard GAC: Has the highest pressure drop. Water must travel from one end of the carbon to the other, which can significantly slow down the flow.
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Carbon Block: These are highly restrictive because they use compressed carbon to filter out fine particles. They offer the lowest flow rates overall, which typically results in the most noticeable pressure loss
Every home is different — pipe size, pressure, and water usage all matter.
We can recommend the right setup based on: 0800040617
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Number of bathrooms
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Household size
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Water pressure
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What you want removed
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