Clack WS1 Water Softener Review (vs Fleck 5600SXT)
Quick answer: a “Clack water softener” is almost always a softener built around Clack’s WS1 control valve, the “brain” on top of the resin tank. Clack sells to equipment makers and distributors, so these systems come from water treatment dealers rather than straight from Clack. Compared with the Fleck 5600SXT, the valve on most do-it-yourself softeners sold online, the Clack WS1 is rated for more flow (27 gpm vs 20 gpm), much stronger backwash (27 gpm vs 7 gpm) and bigger tanks (up to 21 inches vs 12 inches), and it’s certified to NSF/ANSI 44. For a typical home with a 48,000-grain softener, both valves do the job, and complete systems on the same tank are rated about the same. Choose a Fleck if you want to buy online and install it yourself; choose a Clack for a large tank, a high-flow home or a local dealer who will service it.
Our picks:
- Best Fleck softener on Amazon: AFWFilters Fleck 5600SXT 48,000-grain
- Best way to buy a Clack WS1 softener: from a local water treatment dealer
- Clack WS1 repair kit: genuine Clack WS1 rebuild kit
- Fleck 5600 repair kit: Fleck 5600 valve rebuild kit
How we chose: we haven’t installed or tested these valves ourselves. We compared Clack’s and Pentair’s own spec sheets and manuals, and checked how each valve is sold and repaired. Where a figure comes from a seller’s listing, we say so.
What is a Clack water softener?
Clack Corporation, based in Windsor, Wisconsin, makes control valves, resin and brine tanks, filters and other parts for water treatment equipment. Its site says it serves original equipment manufacturers (OEMs) and distributors, and it points buyers to their regional OEM supplier. So a “Clack water softener” is usually a softener a dealer or brand has built around a Clack valve, most often the 1-inch WS1. Clack also makes complete systems of its own, sold through distributors such as Pace Supply.
The valve, sometimes called the softener’s “head,” switches between service and regeneration, measures water use and runs each cleaning cycle. The resin, tank size and brine tank decide capacity. For how those parts work together, see how a water softener works.
Clack WS1 vs Fleck 5600SXT: the specs
| Clack WS1 | Fleck 5600SXT | |
|---|---|---|
| Service flow | 27 gpm at 15 psi drop (with meter and bypass) | 20 gpm continuous at 15 psi drop; 26 gpm peak at 25 psi (valve alone) |
| Backwash flow | 27 gpm at 25 psi drop | 7 gpm at 25 psi drop |
| Softener tank size | 6 to 21 inches across | 6 to 12 inches across |
| Connections | ¾" to 1.5" (NPT, sweat, solvent, push-fit options) | ¾", 1" or 1¼" |
| Meter range | 0.25–27 gpm, ±5% | 0.25–15 gpm, ±5% |
| Regeneration modes | Meter immediate, meter delayed, time clock | Meter immediate, meter delayed, time clock, day of week |
| Double backwash | Standard feature | Available |
| Power outage | Settings kept in nonvolatile memory; battery keeps time for 8 hours | Settings kept in permanent memory; clock keeps time for at least 8 hours (older Pentair documents say 48) |
| Pressure and temperature | 20–125 psi; 40–110°F | 20–125 psi; 34–110°F |
| Drain line | ¾" or 1" NPT | ½" NPT |
| Certifications listed | NSF/ANSI 44, NSF/ANSI/CAN 61 and 372 | UL for the powerhead (Pentair’s spec sheet) |
From Clack’s WS1 spec sheet (form 2572) and product page, and Pentair’s 5600SXT spec sheet (part 42749), product page and manuals. Pentair’s US product page also lists the 20 gpm and 7 gpm ratings.
What the numbers mean for a home
- Flow is rarely the bottleneck. EPA puts a conventional showerhead at 2.5 gpm and a standard faucet at 2.2 gpm, so two showers and a faucet at once use about 7.2 gpm. Both valves have room to spare. In a complete softener, the tank and resin limit flow more than the valve: Pace Supply rates a 48,000-grain Clack WS1 system on a 10 × 54-inch tank at 13 gpm, and AFWFilters lists its 48,000-grain Fleck 5600SXT on the same tank size at 12 gpm.
- Backwash is the real difference. Backwash flow limits how big a tank the valve can clean. The Fleck tops out at a 12-inch softener tank (10 inches for filters); the Clack goes to 21 inches. That matters for large softeners and for iron, carbon or sediment filters, which need strong backwash.
- Certification. Clack lists NSF/ANSI 44 certification for the WS1 valve. Pentair’s 5600SXT spec sheet lists UL approval for the powerhead and no NSF listing; check any complete system’s own certifications.
One caution: some sellers’ comparison pages describe the Fleck 5600SXT as a timer-only valve. It isn’t. Pentair’s spec sheet lists metered immediate and metered delayed regeneration, the same demand-based modes the Clack offers. See regeneration for why that matters.
Clack or Fleck? Quick chooser
Answer four questions to see which valve suits your system.
Answer the questions to see which valve fits.
How it works: the chooser checks each valve’s published limits (softener tanks up to 12 inches and filter tanks up to 10 inches for the Fleck, 21 inches for the Clack; 20 vs 27 gpm service flow), then weighs how each is sold.
Programming, parts and repairs
- Programming. Both have a digital display and store settings through power cuts. Both ask for the same basics: hardness, capacity and regeneration time. Our settings guide walks through the Fleck menus.
- Repairs. Both valves use a piston moving inside a stack of seals and spacers, the parts that wear. Clack’s WS1 uses a one-piece seal and spacer stack (part V3005) and a service wrench (V3193). Fleck’s 5600 uses a seal and spacer kit (60125) and a main piston (60102). Rebuild kits for both are sold on Amazon; see how long softeners last for when a rebuild makes sense.
- Where to buy. Complete Fleck 5600SXT softeners are easy to buy online, including on Amazon. Clack sells through OEMs and distributors, so complete Clack softeners come from water treatment dealers and online water stores; in our search, Amazon mainly listed Clack parts.
Clack valve models
The WS1 is Clack’s 1-inch valve and the one in most home softeners. Clack also makes a twin-alternating version (WS1TT) for two-tank systems, plus 1.25-, 1.5-, 2- and 3-inch valves for bigger homes and commercial systems. For two-tank softeners, see our dual-tank guide.
Which should you choose?
| Choose the Fleck 5600SXT if… | Choose the Clack WS1 if… |
|---|---|
| You want to buy online and install it yourself | You’re buying from a local dealer who installs and services it |
| Your softener tank is 12 inches or smaller | You need a tank larger than 12 inches |
| You want the widest choice of ready-to-ship systems | You want a valve certified to NSF/ANSI 44 |
| A typical home’s flow is enough | You’re also running backwashing filters or need very high flow |
Our picks
AFWFilters Fleck 5600SXT 48,000-grain softener
A complete two-tank system on the Fleck 5600SXT metered valve, popular with do-it-yourself installers.
- Tank and resin: 10 × 54-inch tank with 1.5 cubic feet of resin; 15-inch brine tank (listing)
- Flow: 12 gpm (listing)
- Included: bypass valve and 1-inch plumbing adapter (listing)
Good to know: for smaller homes, DuraWater sells a 24,000-grain Fleck 5600SXT on an 8 × 44-inch tank. Size yours with our size calculator.
Check price on AmazonA Clack WS1 softener from a water treatment dealer
Because Clack sells through dealers and OEMs, the best route to a Clack softener is a local water treatment dealer or an online water store that builds systems on the WS1. A local dealer can also size it to your water and service it later.
- Typical home system: a 48,000-grain softener on a 10 × 54-inch tank with 1.5 cubic feet of resin, rated at 13 gpm in Pace Supply’s listing
- Ask the seller: whether the brine tank and bypass valve are included (Pace Supply’s listing for Clack’s own 48,000-grain system says the brine tank isn’t), the warranty on the valve and tank, and who services it
Good to know: compare the complete system’s certifications and warranty, not just the valve. Our water softener brands guide compares warranties and support.
See the WS1 at ClackClack WS1 rebuild kit with service wrench
The listing describes genuine Clack parts: the V3005 seal and spacer stack, the V3011 main piston, the V3174 regenerant piston and the V3193 service wrench used to open the valve.
- Fits: WS1 valves (check your valve’s piston type before ordering)
Good to know: sold by a third-party water treatment store; check that the parts match your valve’s model and flow direction.
Check price on AmazonFleck 5600 softener valve rebuild kit
A kit with the main piston (60102-00), seals and spacers (60125) and brine valve (60032) for the Fleck 5600 valve.
Good to know: the softener piston (60102-00) is different from the filter piston (60102-10), so check your valve first.
Check price on AmazonFrequently asked questions
Is Clack better than Fleck?
On paper, the Clack WS1 has more flow, much stronger backwash, room for bigger tanks and an NSF/ANSI 44 certification. For a typical home softener on a 10-inch tank, though, both work well, and the Fleck is easier to buy online. Choose by how you’ll buy, install and service it.
Where can I buy a Clack water softener?
From water treatment dealers and online water stores that build systems on Clack valves. Clack’s own site doesn’t sell online; it serves OEMs and distributors and points buyers to their regional OEM supplier.
What size Clack softener do I need?
Size by hardness and water use, not by valve. A 48,000-grain system on a 10 × 54-inch tank is common for many homes; use our size calculator for yours.
Can I replace a Fleck valve with a Clack valve?
Often. Both valves thread onto the standard 2½-inch tank opening (2½"-8 NPSM). The Clack takes a 1.050-inch distributor tube, while Fleck systems use either a 13/16-inch or a 1.050-inch tube, so you may need a new tube. The bypass and plumbing adapters also differ. Ask the seller or a dealer to confirm the parts for your tank before switching.
How long do Clack and Fleck valves last?
Both are rebuildable, and seals and pistons are the parts that wear. See how long water softeners last.
Related guides
- Best water softeners
- Best water softener brands
- Best dual-tank water softeners
- How to install a water softener
Sources
- Clack Corporation, WS1 Water Specialist Valve and WS1 spec sheet (form 2572), control valves and home page (OEMs and distributors).
- Pentair, Fleck 56SXT Softener Meter product page, 5600SXT spec sheet (42749), 5600SXT downflow manual and SXT control manual.
- Pace Supply, Clack WS1 Water Softener System, 48,000 grains listing.
- U.S. EPA WaterSense, Showerheads and Bathroom Faucets.
- Amazon listings for the AFWFilters, DuraWater and rebuild-kit products, checked October 2026.