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Harvey Minimax M3
Harvey Minimax M3
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Harvey Minimax M3

Classic Performance and Proven Reliability

The MiniMax M3 fitted neatly under a kitchen sink.

The UK’s most tried‑and‑tested water softener, the MiniMax M3 marked a major leap forward in domestic water treatment. When it was released, it set a new benchmark for reliability, performance, and efficiency — and helped Harvey Water Softeners become Europe’s leading manufacturer.

While the 5th Generation environmentally friendly MiniMax Innova has since taken centre stage, the 4th-generation MiniMax M3 remains a firm favourite.

It’s still available through Hydroworks — either supply only for DIY installation, or fully supplied and installed by our expert team.

Why Choose the MiniMax M3?

  • Continuous flow rate: 56 litres per minute
  • Peak flow rate: 65 litres per minute
  • Ultra-low water usage: Just 17.1 litres per regeneration
  • Uses Harvey Original block salt — clean, compact, and convenient
  • Ideal for up to 10 people with two bathrooms
  • No compromises between flow rate and efficiency
  • Includes a 10-year manufacturer-backed parts guarantee
  • Compact dimensions: (W)206mm x (H)490mm x (D)445mm
The Minimax M3 is an extremely efficient and reliable water softener with a 10-year guarantee when fitted by Hydroworks.

Advanced Features

These are some of the features of the MiniMax M3:

Smart Shuttle Metering

Breakthrough technology that measures water usage with precision, regenerating only when needed — no waste, no guesswork. Built for all UK plumbing systems, including loft tanks, combi boilers, and high-pressure unvented systems.

Low-Pressure Injector

Even if your home has lower water pressure or pressure fluctuations (e.g. during peak usage), the M3 keeps working at its best — delivering consistent performance without compromise.

High Flow Rates

Unlike older softeners that force you to choose between flow or efficiency, the M3 gives you both. Enjoy fast, uninterrupted water — even with multiple taps running.

Stress Tested Beyond Industry Standards

The M3 has been tested to over 1 million cycles at 15 bar pressure — a huge leap beyond the UK standard. This means decades of reliable service, even in demanding homes.

An internal view of the Minimax M3 showing the twin-cylinder, non-electric system.
How do I top up the Minimax M3 with salt? The salt bay has a red line. If you see the line, you can easily get another block of salt in and still get the lid on.