The single tank water softener employs one tank of resin, and is the most common type of domestic softener. For the resin to be regenerated, the tank needs to be taken out of service and a bypass valve opened. For this reason, while the regeneration takes place (which normally takes 30 – 60 minutes), only hard water is available, therefore the regeneration usually is programmed to occur during the night.
A lot of water softeners operate on a time control basis. A timer is the simplest form of control and is usually the less expensive option. The timer control calculation includes the number of days that the system will operate, the number of people in the house, the capacity of the softener and the hardness of the water supply – and then the softener is set to regenerate at a certain time of the night at this calculated frequency.
Regardless of the volume of the water used, the system which operates on a time control basis, will regenerate at the pre-set number of days. It is advisable that the water softener is switched off if it is not going to be used for a period of time, such as holidays.
A volume-controlled water softener system is designed to adjust to the demand and to avoid over or under regenerating the softener. It will regenerate when the pre-set volume of water used has been achieved.
Some control systems are programmed to monitor daily water usage and ensure that regeneration takes place on the best possible night, to make sure that softened water is always available. This also saves on water and water softener salt used during the regeneration. The “proportional brining” technique is used to measure the actual quantity of water used before each regeneration and to control the amount of brine used for that regeneration. This ensures the restoration of resin capacity and helps to use salt and water more efficiently.
A two-tank water softener system uses two resin tanks: when one is in service, the other one is on standby. The control system monitors the water flow and switches the flow to the other tank after the first tank is exhausted, and regenerates the first tank while the second one is working. That ensures that the soft water is available even during regeneration, and system continues to swap from one tank to the other, regenerating when necessary.
The twin tank water softener system regenerates on volume, and the full capacity of the resin is used for each service cycle.
Some brands have a non-electric control head, and use water pressure to operate the valves and measure the flow to monitor the volume of water used.