Single or double softening system (Basic vs Duplex)

Table of Contents

• What is a pressure tank?
• What happens in the pressure tank?
• What good is a second tank?
• Conclusion

Softening systems are offered as single or double systems. The systems differ in the number of pressure tanks and ultimately also in the price. Why is there this difference and what are the advantages and disadvantages?

What is a pressure tank?

A pressure tank is basically a container that can withstand a certain amount of pressure. This tank contains the exchange resin, which exchanges calcium and magnesium ions for sodium ions. A single softener has one pressure tank and a double softener has two of these tanks.

What happens in the pressure tank?

Depending on the size of the tank, a system has a certain capacity to absorb calcium and magnesium. As the hard water flows through the tank, the resin loses its capacity and needs to be regenerated. The systems are usually dimensioned so that this takes place every three days. During regeneration, the tank is flushed fully automatically with salt water so that the resin regains its full capacity. During this phase (approx. 1 to 2 hours) this tank cannot soften the water. For individual systems, this regeneration is carried out at night if possible. In the case of double systems, the control switches immediately to the second tank. You can find a detailed description of this process here: How a softening system works in detail

What good is a second tank?

A second tank bridges the regeneration pause and also gives the system greater efficiency. By switching to the second tank during the regeneration break of the first tank, there is practically no regeneration break and thus an uninterrupted supply of soft water is guaranteed.

A small buffer is always programmed into the individual systems so that it is always regenerated at night and still has enough reserves available during the day to soften the water. However, if you stop using water until night, the system may regenerate even though there would still be some remaining capacity left. This reserve does not exist with double systems. This means that double systems use salt more efficiently.

Conclusion

Softening systems with a pressure tank are cheaper to purchase and require a little more salt if water consumption fluctuates. Double systems make optimal use of the capacity and require a little less salt, especially when consumption fluctuates. They also provide uninterrupted soft water, but are a little more expensive to purchase. Individual systems make sense in single-family homes if consumption does not fluctuate significantly and soft water can be dispensed with at night. Double systems make sense in apartment buildings, hotels and in industry if consumption fluctuates greatly and/or soft water needs to be delivered reliably.