Watts Stacked Dual Tank Water Softener


MSRP: $1,995.00 $1,595.00


SKU: Watts Stacked - STI

Product Description


  • Water Softener and Filter All-in-One – 30,000 grain Capacity
  • Carbon Filtration to Remove Chlorine and VOCs
  • On-Demand Meter That Learns Water Usage to Regenerate Only When Needed


This Dual Tank Water Softener Provides Soft, Clean, Filtered and Refreshing Water for You and Your Family

Water Softener and Filter All-In-One Make buildup a thing of the past with the Watts Stacked - STI

The Watts Stacked Dual Tank Water Softener is a combination water softener and filter all-in-one.

 It softens your water so cleaning is easier, soap lathers better, while requiring less detergent and helping to reduce water spots. The Watts water softener also protects water-using equipment (water heaters, dishwashers, washing machines) from hard water damage and scale build-up.

Make scale build-up and staining a thing of the past with this dual tank water softener

The Watts Stacked water softener and filter also has granular activated carbon (GAC) filtration to remove chlorine and VOCs (pesticides, herbicides, chemical contaminants), bad taste and odors from your water. You use salt (or potassium if you prefer) to maintain the softener as needed. Your water will be soft and taste great.

Dual tank water softener ships fully programmed for your convenience. The Watts water softener and filter is easy to install.


Dual Tank Water Softener Features:

* Easy Installation

* Economical pricing

* Vertical dual tank design

* Dual media capacity

* Separation screen to prevent media migration

* Extended resin life

* Dome holes for easy media access

* Minimal service parts

* Top quality components

* Metered valves for greater efficiency

* Softener capacity to 30,000 grains

* Double backwash for optimum results

* Treated water for regeneration re-fill

* 12 volt AC adapter for easy installation

* By-pass included (1)



Q: Will my water feel slippery-soft using the Watts STI water softener and filter?
A: Yes, the Watts STI completely removes the minerals providing a slippery soft feel.

Q: Can I use Potassium instead of salt as a regenerate?

A: Yes, you can use either one or the other and in fact you can mix the two if you prefer.

Q: Where can I buy the salt or potassium needed to regenerate this system?

A: You can pick up rock salt or potassium locally at any local hardware store.

Q: Does this system provide filtration for contaminates like Chlorine and VOC’s?
A: YES, this system uses coconut shell carbon designed to remove chlorine and VOC’s.

Q: Can I use this system to treat my iron issues?

A: The Watts STI water softener will remove small amounts of iron and manganese however we do not recommend treating an iron issue with a water softener if you have a lot of iron but hard water is not an issue. We have a great iron removal system that is maintenance free.  Click here for more details.

Q: Will the Watts STI system remove “rotten-egg smell” caused by sulfur?
A: No, this system is not designed to address sulfur in any way. We do however have several systems that will address sulfur issues, please ask our friend experts for advice on which system is best for you.

Q: How long will the softening resin last?

A: We use a high capacity softening resin that will last on average 10 years.

Q: How long will the carbon media last?
A: Two years on average

Q: How much water is used in the regeneration process?

A: This system will use an average of 100 gallons of water per regeneration process.

Q: Does the Watts STI require electricity?

A: Yes, this system will come with a standard 110 volt plug.


Filtration Information:

The Watts Stacked Softener has granular activated carbon (GAC) filtration to remove chlorine and VOCs (pesticides, herbicides, chemical contaminants), bad taste and odors from your water.


Valve:         Metered (solid state microprocessor)

Cycles:     6

Flow rate (service):     27 gpm @ 15 psi drop with by-pass

Flow rate (BW):     27 gpm @ 25 psi drop with by-pass

Valve body:     Noryl® plastic

Pipe size:     1″

By-pass:     included (plastic)

Mineral tanks:     10″ X 54″ Vortech (NSF Certified)

Brine tanks:     18″ X 36″ Polypropylene, assembled

Media (top):   
 Premium grade activated carbon

Media (bottom):     Cation resin; chlorine resistant


More Information


Watts Installation Instructions


Watts Operation/Programming Manual



  • Weight: 124 lb
  • Width: 5 in
  • Depth: 5 in
  • Height: 5 in

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