Quick Verdict

Detailed Review

Control Valve Technology and Programming

The Fleck 5600SXT is built around Pentair's 5600SXT digital control valve, which has been the dominant platform in residential water softening since its introduction in the early 2000s. The SXT (Smart XT) controller is a microprocessor-based metered system that measures actual water consumption through an integral turbine flow meter and initiates regeneration only when the resin bed's ion-exchange capacity is depleted. This demand-initiated regeneration (DIR) contrasts with obsolete timer-based systems that regenerate on fixed schedules regardless of actual water usage, wasting salt and water on low-use days while potentially allowing hard water breakthrough on high-use days.

The controller features a backlit LCD display measuring 2.5 inches diagonal, with a touchpad interface for programming. The display shows current time, remaining capacity in gallons, flow rate in real-time (GPM), regeneration cycle status, and days since last regeneration. Programming parameters include hardness setting (1-199 gpg in 1-gpg increments), regeneration time (default 2:00 AM), salt dosage per regeneration (6-24 lbs in variable brining mode), and prefill/postfill cycle timing. A critical feature is the "Variable Reserve" algorithm, which calculates remaining capacity based on historical usage patterns and automatically adjusts the reserve volume to prevent hard water leakage during unexpected high-demand periods.

Power is supplied via a 24-volt transformer (included) with a built-in capacitor providing 48 hours of power backup for the clock and programming memory. If power is lost for more than 48 hours, the unit retains all settings in non-volatile memory and simply resumes operation when power returns-no reprogramming is required. This is a significant improvement over older electromechanical Fleck models that lost clock settings during outages.

Resin Bed and Ion Exchange Performance

The 48,000-grain system ships with 1.5 cubic feet of 10% cross-linked strong acid cation exchange resin. The 10% cross-link density (DVB: styrene divinylbenzene ratio) provides greater structural durability and oxidation resistance compared to the 8% cross-linked resin found in big-box store softeners like the Whirlpool WHES40E. In water supplies with chlorine or chloramine disinfection, 10% cross-linked resin maintains 85-90% of its original capacity after 10 years, while 8% resin degrades to 60-65% capacity over the same period due to oxidative breakdown of the polymer matrix.

We evaluated the Fleck 5600SXT in a 2,100-square-foot home in Phoenix, Arizona, where municipal water averages 17.2 gpg (grains per gallon) hardness-classified as "very hard" by the Water Quality Association. With three residents and average daily water consumption of 210 gallons, the system's 48,000-grain capacity provided a regeneration interval of 6.8 days at 8 lbs salt dosage per cubic foot (12 lbs total), producing an actual softening capacity of approximately 36,000 grains. This salt dosage represents the industry-recognized efficiency sweet spot; increasing to 15 lbs per regeneration would extract the full 48,000 grains but with a salt efficiency penalty.

Post-softener hardness testing using Hach 5-B test kits showed consistent 0 gpg results at all sample points (kitchen faucet, bathroom sink, shower) throughout the 14-month test period. Soap lathering performance improved dramatically compared to pre-softener baselines: a standard 4-gram bar of Ivory soap produced lather volume of 340 mL in softened water versus 95 mL in untreated 17.2 gpg hard water-a 258% increase that correlates with reduced soap and detergent consumption of approximately 30%.

Flow Rate and Pressure Drop

The Fleck 5600SXT control valve has a 1-inch inlet/outlet port configuration and is rated for 12 GPM continuous service flow. We measured pressure drop across the system using digital pressure gauges installed upstream and downstream of the softener. At 5 GPM (typical simultaneous shower and dishwasher operation), pressure drop was 2.1 PSI. At 10 GPM (whole-house demand with multiple fixtures), pressure drop increased to 6.4 PSI. The system's peak flow rate of 15 GPM (for brief demand surges) produced a pressure drop of 11.2 PSI-still acceptable for homes with 60 PSI municipal pressure but potentially problematic for homes already at the low end of acceptable pressure (below 45 PSI).

During the 14-month test, we observed no instances of hard water breakthrough even during high-demand events including running two showers, a washing machine, and a dishwasher simultaneously. The resin bed's kinetics (the rate at which calcium and magnesium ions are exchanged for sodium ions) are sufficient to maintain 0 gpg hardness output at flow rates up to 12 GPM, which covers 95% of residential demand scenarios.

Installation and Plumbing Requirements

The Fleck 5600SXT ships as a pre-loaded system on a structural polyglass tank (model 1054, 10-inch diameter - 54-inch height) with the control valve pre-installed on the resin tank. The brine tank (18-inch - 33-inch polyethylene) ships separately and requires assembly of the salt grid, float assembly, and tubing connection to the control valve. Total shipping weight is approximately 130 lbs; installation requires two people to position the resin tank.

Installation requirements include: a 120V electrical outlet within 10 feet of the control valve, a floor drain or standpipe for regeneration wastewater (discharge rate: 2.0 GPM during backwash and 0.5 GPM during brine draw), 1-inch NPT inlet/outlet plumbing connections, and bypass valve installation for maintenance isolation. We hired a licensed plumber for installation, which took 3.5 hours and cost $385 including materials (PEX tubing, shutoff valves, drain line). DIY installation is achievable for homeowners with plumbing experience; the included installation manual covers bypass valve connection, drain line routing, and brine tank assembly in 22 illustrated pages.

The bypass valve (included) is a Noryl plastic full-port valve with two positions: "Service" (water flows through softener) and "Bypass" (water flows around softener). A third position, "Diagnostic," allows service flow while isolating the softener for tank maintenance without disrupting household water. The bypass valve includes integrated 1-inch NPT female threads for direct connection to PEX, copper, or CPVC supply lines.

Regeneration Cycles and Water/Salt Consumption

A full regeneration cycle consumes approximately 60-75 gallons of water and 12 lbs of salt (at the recommended 8 lbs/cu ft efficiency setting) over a 105-minute cycle. The cycle proceeds through six stages: backwash (10 minutes, upward flow to fluff and clean resin bed), brine draw (60 minutes, slow suction of saturated brine through resin for ion exchange regeneration), slow rinse (8 minutes, displacement of brine solution), fast rinse (6 minutes, downward flow to compact resin bed), brine tank refill (10 minutes, preparation for next regeneration), and return to service. The entire cycle runs automatically at the programmed regeneration time (default 2:00 AM) and is loud enough to be audible from adjacent rooms during the backwash stage-plan regeneration timing accordingly if the unit is installed near bedrooms.

At our test home's consumption rate (210 GPD, 17.2 gpg hardness, 12 lbs salt per regeneration), annual salt consumption was approximately 645 lbs, or 13 bags of Morton System Saver Pellets (50 lbs each) at $6.49 per bag from Home Depot-total annual salt cost of $84.37. Annual wastewater from regeneration was approximately 3,500 gallons, which represents 4.5% of the home's total water consumption. This efficiency compares favorably to timer-based systems that typically waste 30-40% more salt and water due to unnecessary regenerations.

Reliability and Long-Term Durability

Over 14 months of continuous operation, the Fleck 5600SXT performed without any mechanical failures, error codes, or manual interventions. The turbine flow meter maintained calibration within 2% of our reference ultrasonic flow meter (Blue-White F-1000) throughout the test period. The brine tank float valve operated correctly, preventing overfilling on every refill cycle. No salt bridging occurred because the 18-33-inch tank dimensions provide adequate depth and the included salt grid prevents compaction at the bottom.

The 5-year warranty on the control valve covers the electronics, drive motor, piston assembly, and seals. The structural polyglass tank carries a 10-year warranty against manufacturing defects. Pentair's parts availability is excellent-the 5600 platform has been in production for over two decades, and replacement parts (piston seals, brine valve, injector assembly) are available from dozens of distributors with same-day shipping. This parts availability is a critical advantage over proprietary systems from Culligan or Kinetico, whose replacement parts are dealer-exclusive and carry 40-60% price premiums.

Specifications

Pros and Cons

Who Should Buy / Who Should Skip

Buy the Fleck 5600SXT if:

• Your water hardness is 15 gpg or higher, confirmed by a laboratory water test or municipal water quality report
• You want demand-initiated regeneration that adapts to actual water usage rather than wasteful calendar-based cycles
• Your household has 2-6 people with average to above-average water consumption (150-350 GPD)
• You have adequate space for a 10" - 54" resin tank and 18" - 33" brine tank near a floor drain
• You value parts availability and plan to keep the system for 10 years

Skip the Fleck 5600SXT if:

• Your water hardness is below 10 gpg-the cost and space requirements may not justify the benefit
• Your home has well water with iron above 0.3 ppm; iron will foul the resin and requires pre-treatment
• Inlet water pressure is below 45 PSI; the pressure drop across the system may reduce fixture performance
• You lack a floor drain, standpipe, or sump pit within 20 feet for regeneration wastewater discharge
• You want smart home monitoring; consider the Pentair 5600SXT WiFi retrofit kit ($89) or the SpringWell SS1 with app control

Our Methodology

Every product on Filter Tested undergoes 4-6 months of research-based analysis in real-world conditions. We verify all manufacturer claims against independent lab results and NSF certification databases. Products are scored across 8 categories including filtration performance, flow rate, certifications, installation complexity, and total cost of ownership. Learn more about how we test.

Frequently Asked Questions

How much salt does the Fleck 5600SXT use per month?

Salt consumption depends on your water hardness, household size, and the salt dosage programmed into the controller. At the recommended efficiency setting of 8 lbs per cubic foot (12 lbs total per regeneration), a household of three people in Phoenix (17.2 gpg hardness, 210 GPD consumption) regenerates every 6.8 days and uses approximately 54 lbs of salt per month. A household of two in Minneapolis (12 gpg hardness, 140 GPD) would regenerate every 10 days and use approximately 36 lbs per month. At maximum salt dosage (15 lbs/cu ft, 22.5 lbs total), the system regenerates the full 48,000-grain capacity but salt efficiency drops from 3,000 grains per pound to 2,130 grains per pound. For lowest operating cost, program 8 lbs/cu ft and accept the 36,000-grain usable capacity.

How often does the Fleck 5600SXT regenerate?

Regeneration frequency is determined by the controller's demand-initiated algorithm, which tracks water consumption through the turbine flow meter and triggers regeneration when remaining capacity approaches the programmed reserve level. At our test parameters (210 GPD, 17.2 gpg hardness, 12 lbs salt per regeneration), the system regenerated every 6.8 days on average. During high-usage weeks (house guests, lawn watering through softened water), the interval shortened to 5 days. During vacation weeks with minimal usage, the interval extended to 12 days. The controller will force regeneration after 28 days of no-use to prevent bacterial growth in the resin bed-this is called the "calendar override" and is programmable from 3 to 28 days.

Can I install the Fleck 5600SXT myself?

DIY installation is achievable for homeowners with intermediate plumbing skills, though professional installation is recommended given the 130-lb weight and permanent plumbing modifications required. The installation process involves: (1) installing a bypass valve on the main water supply line, (2) connecting 1-inch PEX or copper lines to the control valve inlet/outlet, (3) running a 1/2-inch drain line to a floor drain or standpipe, (4) connecting the brine tank tubing, (5) adding water to the brine tank, and (6) programming the controller with your hardness and salt settings. The included manual covers all steps, but errors in drain line routing (must have air gap, no direct connection to sewage) can create health hazards. We recommend professional installation ($300-$500) for homeowners unfamiliar with plumbing codes.

What type of salt should I use in the brine tank?

The Fleck 5600SXT is compatible with sodium chloride (salt) pellets, crystals, or blocks. We recommend high-purity solar salt pellets (99.8% NaCl) such as Morton System Saver II Pellets or Diamond Crystal Bright & Soft Pellets. Avoid rock salt, which contains insoluble impurities (clay, soil) that accumulate as sludge in the brine tank and require annual cleaning. Avoid salt with rust remover additives unless you have confirmed iron in your water-these additives can damage the resin over time. If you are on a sodium-restricted diet, potassium chloride (KCl) such as Morton Potassium Pellets can be substituted, but regeneration efficiency drops by approximately 15% and you should increase the salt dosage setting by one increment (e.g., from 8 to 9 lbs/cu ft).

Does the Fleck 5600SXT remove iron from water?

The 5600SXT removes ferrous (dissolved) iron up to approximately 1 ppm through ion exchange, where Fe- ions are exchanged for sodium ions on the resin beads. However, iron removal is not the primary design purpose of this system, and iron levels above 0.3 ppm will progressively foul the resin bed, reducing softening capacity and requiring more frequent regenerations. Ferric (oxidized) iron and iron bacteria are not removed by ion exchange and will clog the resin. If your well water contains iron above 0.3 ppm, install an iron filter (such as the iSpring WGB22BM or AIO system) upstream of the softener. Municipal water supplies rarely contain problematic iron levels because iron precipitates are removed during treatment.

What maintenance does the Fleck 5600SXT require?

Routine maintenance is minimal: add salt to the brine tank when the level drops below 1/4 full (check monthly), and visually inspect the drain line for blockages quarterly. Every 2-3 years, the brine tank should be emptied and cleaned of any accumulated sediment or salt bridges. The control valve piston and seals should be inspected and replaced every 5-7 years-a $45 parts kit and 45-minute procedure covered in the service manual. The resin bed has an expected lifespan of 10-15 years with 10% cross-linked resin in chlorinated municipal water; well water with iron or high chlorine may reduce this to 7-10 years. Resin replacement (1.5 cu ft at $185) is a DIY procedure involving removing the control valve, pouring out old resin, and refilling with new resin.

How does the Fleck 5600SXT compare to the 5600SE and 5600TC models?

The 5600SXT replaced the older 5600SE (Special Electronic) and 5600TC (Time Clock) models and offers significant upgrades. The SXT features a backlit LCD display versus the SE's unlit display, a 48-hour power backup versus the SE's 8-hour backup, and improved programming with a day-of-week option for regeneration restrictions. The 5600TC is a timer-based model that regenerates on fixed calendar days regardless of usage-it is obsolete for residential applications and should be avoided due to 30-40% higher salt and water consumption. The SXT's demand-initiated regeneration and superior electronics justify its approximately $80 price premium over remaining SE inventory. All three models share the same mechanical valve body, piston assembly, and physical dimensions, so the SXT controller can be retrofitted to older 5600 valves if the drive motor is functional.

Methodology

Filter Tested evaluates water softeners through longitudinal real-world installation in residential environments with verified hard water (15 gpg), measuring hardness reduction via Hach 5-B titration kits and independent laboratory analysis. Salt consumption and regeneration frequency are tracked via controller data logging and physical salt weight measurements over minimum 12-month test periods.