Twin Tank Water Softeners
Twin tank water softeners are systems that are built with two softening tanks controlled by a single control valve mechanism. Twin tank softeners are operated in a twin-alternating pattern: water softening flip-flops between the two tanks as they each become exhausted. These systems have the ability to regenerate one tank while the other is in service, creating an uninterruptible and unlimited soft water supply.
Twin tank water softeners are used where water is so hard that a single tank system cannot get through a single 24-hour period without becoming exhausted. They are also used in commercial situations where a 24/7 supply of soft water is required but a regeneration window doesn't exist. Twin tank softeners have a built-in side-benefit of offering unparalleled salt efficiency and are sometimes selected for this reason alone.
Aquatell is proud to offer twin tank systems featuring the Clack WS1EE and Fleck 9100SXT control valves. We generally find the Clack-based system easier to install, program, and maintain, and it has been a more reliable system in our experience. When evaluating our twin tank systems, please note that we name our systems based on the volume of resin used per-tank not the total volume combined in both tanks.
When Should I Consider a Twin Tank System?
Most residential homes don't need a twin tank softener, rather a properly sized single tank system is the better choice for price and softening performance. Twin tank systems earn their cost in two specific situations: when water hardness is extreme enough that a single tank can't get through a full day without running out of capacity (generally above 40 grains per gallon), or when there's no reliable overnight window for regeneration, such as shift-work households or 24/7 commercial use. Twin tank systems also edge out single tank systems slightly on salt efficiency, since they run each tank's capacity fully down before regenerating.
Read the full breakdown of twin tank vs. single tank softeners
Frequently Asked Questions
Twin tank softeners typically cost about double the equivalent single tank system, the extra cost covers the second softening tank, the connecting hardware, and the twin-alternating control valve that coordinates the two tanks.
Yes. A twin tank system needs room for two softening tanks side by side, plus the brine tank, so its footprint is larger than a single tank system's.
The main downsides are the higher upfront cost and larger footprint. There's also a subtle performance tradeoff: splitting the softening resin into two tanks means only one tank treats water at a time, so peak flow-rate softening performance is slightly lower than a single tank built with the same total resin volume, though this rarely matters outside high flow-rate demands.
They use slightly less salt, since each tank fully depletes its capacity before regenerating rather than regenerating early with capacity to spare. Water use is proportional to resin capacity either way, so there's no meaningful water-use difference between the two designs.
Yes. Twin tank systems are common in 24-hour carwashes, bakeries, and factories, anywhere a continuous supply of soft water is required and there's no consistent window for regeneration.
Aquatell's twin tank softeners are built with either the Clack WS1EE or Fleck 9100SXT control valve. We generally find the Clack-based system easier to install, program, and maintain, and it's been more reliable in our experience.