Simplex and Duplex Water Softeners


What is the difference between Simplex and Duplex softeners?

Simplex and Duplex are terms used in water softener devices these are designed to remove minerals, primarily calcium and magnesium ions, from hard water through a process called ion exchange. Softened water can prevent the build-up of scale in pipes and appliances, improve the efficiency of water heaters, and provide other benefits. There are two main types of water softeners: simplex and duplex.

Simplex Water Softeners:

Single Tank System: Simplex water softeners consist of a single resin tank where the ion exchange process takes place. Hard water enters the tank, and the resin beads inside the tank attract and remove the calcium and magnesium ions, replacing them with sodium or potassium ions.

Regeneration: After a certain amount of water passes through the resin tank and the resin beads become saturated with hardness ions, the system needs to regenerate. During regeneration, a brine solution (usually made from water and salt) is passed through the resin tank. The brine solution displaces the accumulated hardness ions, which are then flushed out of the system. This process restores the resin beads’ ability to soften water.

Downtime during Regeneration: One drawback of simplex systems is that they need to go through the regeneration process, during which they are temporarily offline. This downtime can be a concern if softened water is needed continuously.

Duplex Water Softeners:

Dual Tank System: Duplex water softeners consist of two resin tanks. While one tank is in use, the other tank is in regeneration mode. This allows for a continuous supply of softened water, as one tank is always online, even when the other is regenerating.

Continuous Operation: The key advantage of duplex systems is their ability to provide a constant supply of softened water without interruption. When one tank is in regeneration, the other tank takes over, ensuring a continuous flow of softened water.

Higher Initial Cost: Duplex systems are typically more expensive than simplex systems due to the added complexity of having two tanks. However, the continuous operation and uninterrupted water supply can outweigh the higher upfront cost in certain applications.

What are some applications and benefits where a water softener would be used? 

A laundry shop:

  • See an increase in laundry and machine efficiency as softened water is more effective in removing stains and preventing mineral build-up. With hard water decreasing heating efficiency by nearly 50%!
  • Reduce soap/detergent usage as far less is needed to get the same effect meaning less detergent is expelled into rivers and streams and also helps save your customers money on detergent.

A car wash:

  • Reduced mineral build-up protects all of your washing equipment and helps prevent spots and streaks from being left over after drying on cars.
  • Get more value out of your soap and other washing products, leading to cost savings over time.


  • Improved cleanliness overall with no mineral deposits on tiles, shower screens, and flooring as well as enhancing laundry quality with softer fresher sheets, energy savings, and protecting appliances.
  • Hotels that serve fine crystal dishes or cutlery will see a large reduction in residual marks left over from washing.

Should I choose a simplex or duplex softener?

One drawback of simplex systems is that they need to go through the regeneration process, during which they are temporarily offline. If you are a business or residence that needs softened water continuously, then we would advise you to purchase a duplex softener.

In summary, simplex water softeners use a single tank and need to go through regeneration, leading to potential downtime. Duplex water softeners, with their dual-tank design, offer a continuous supply of softened water by alternating between tanks during regeneration, making them suitable for applications where a constant water supply is essential.


Simplex Softeners

Clack Duplex Water Softeners

Duplex Softeners

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