Single Tank, Electric Timer Water Conditioners
perform all functions automatically, but rely on an electric timer that initiates regeneration at preset intervals (usually every other day at 3:00am), no matter how much of the system's capacity has been used. Regeneration can occur too often and decrease efficiency, or not often enough and allow hard water into the home. Since these units typically employ only a single softening tank, only hard water is available to the home when they regenerate.

Single Tank, Electric Demand Water Conditioners
measure water usage to determine the best time to regenerate. But such systems are typically not as efficient as systems that employ two resin tanks. If regeneration is necessary at a time of the day when soft water may be needed, they must wait until a more appropriate time to regenerate so hard water isn't introduced into the home. To do so, single tank DIR units must employ a reserve capacity of softening resin to make it through the rest of the day. If the reserve isn't enough, the home will be forced to use hard water until the system regenerates. If the reserve is too large, the system won't be used to capacity but regeneration will occur anyway, wasting water and regenerant.

Twin Tank, Non-Electric Demand Water Conditioners
Twin tank systems measure water usage and regenerate only when the system has been used to capacity for optimum efficiency. Because twin tank systems automatically switch from tank to tank as they exhaust, they are able to provide a continuous supply of conditioned water, 24 hours a day. Some systems even use soft water to clean themselves to improve efficiency. Countercurrent regeneration also improves the systems' effectiveness. This process, which is recommended by most resin manufacturers, regenerates the resin beads more efficiently by reversing the flow through the system during the cleaning process.

Leading consumer publications including Consumers Digest have recognized that non-electric, twin tank DIR water conditioners have distinct advantages over those that operate with electricity. Electronic components are the most frequent things to malfunction on electric systems and can be expensive to repair. Non-electric systems do not suffer from such problems and are not susceptible to power outages.