Twin Tank Water Softeners
A twin tank water softener is a system that has two softening tanks operated by a single control valve mechanism. Twin tank softeners operate in a twin alternating arrangement: water softening flip flops between the tanks and one tank can be regenerated while the other is in service. This creates an uninterruptible and unlimited supply of soft water even in very extreme hardness conditions.
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 side-benefit of offering unparalleled salt efficiency and are sometimes selected for this reason alone.
When Should I Consider a Twin Tank System?
Most residential homes don't need a twin tank softener. Usually a properly sized single tank system is the better choice for softening performance and price. Twin tank systems earn their higher price point 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
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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 style control valve that coordinates the two tanks.
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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.
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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.
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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.
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Yes. This is the common application for a twin tank system. They're commonly used in 24-hour carwashes, bakeries, factories, and anywhere a continuous supply of soft water is required and there's no consistent window for regeneration.
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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.
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It depends on the size. For the twin 1.0 and 1.5 systems, we'd typically ship these by courier with the media packed in the tanks. For twin tanks larger than this, we'd usually ship the system on a pallet and by LTL (truck). There are exceptions, but this describes the typical shipping method.
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The DIY-friendliness of a twin tank (especially Clack based) is no different than a single tank. There are a few more connections to make between the two softening tanks and other than that the installation is identical to a single tank system. The Clack control valve comes pre-programmed and all you ned to do is set the local hardness value.