Quick Answer: The Clack WS1 control valve is Fleck’s main rival, and on raw specs it often wins — dealer comparisons commonly cite roughly 27 GPM flow versus 19-21 GPM for a Fleck 5600SXT, plus support for mineral tanks up to 16 inches versus the 5600SXT’s 14-inch ceiling. The catch is access: Clack Corporation sells almost entirely through OEM assemblers and trade-login dealer accounts rather than direct online retailers, so a complete WS1 system typically runs $1,200-$2,500 installed through a dealer, while comparable Fleck-valve systems are commonly listed on Amazon for $650-$1,500. Unless you’re already shopping dealer-installed, Fleck remains the easier buy.
Every brand review on this site eventually runs into the same control valve twice: Fleck. Our own Fleck water softener guide explains that Fleck doesn’t sell softeners directly — Pentair, which bought Fleck Controls in 1995, licenses the valve out to independent assemblers who build it into their own tanks. What that guide doesn’t cover is Fleck’s actual competitor in that same OEM-valve market: Clack. Zero prior mentions of Clack exist anywhere on this site despite it being the valve independent dealers reach for when a household needs more flow or a bigger tank than a 5600SXT comfortably handles.
Clack vs Fleck, at a glance
| Spec | Clack WS1 | Fleck 5600SXT |
|---|---|---|
| Flow rate | ~27 GPM (cited) | ~19-21 GPM (cited) |
| Max tank diameter | 16 in | 14 in |
| Regeneration cycles | Up to 9 stages, incl. upflow brining | Fewer cycles, 14-day calendar override |
| Where it's sold | OEM assemblers, dealers, trade-login wholesale | Dozens of independent assemblers, widely listed on Amazon |
| Typical complete-system price | $1,200-$2,500 (dealer-installed) | $650-$1,500 (DIY, online) |
| Parts availability | Thinner, mostly dealer-sourced | Deep, cheap, stocked by many suppliers |
Independent water-treatment retailers differ on the exact numbers (one comparison puts the 5600SXT’s ceiling closer to 20 GPM, another closer to 21), and several of the pages making these claims are run by companies that also sell Clack-valve systems, so treat the flow-rate gap as directionally real rather than exact. What’s consistent across every source is the direction: Clack wins on throughput and tank size, Fleck wins on price and parts.
Who makes Clack, and why it’s structured this way
Clack Corporation is a family-owned manufacturer headquartered in Windsor, Wisconsin, with roots tracing back to a small Madison water-softener exchange business the Clack family started in the 1940s. The company is still run by the Clack family today, which puts it in the same small “never sold to a conglomerate” category as Hellenbrand on this site, rather than the acquired-brand pattern behind Hague (A.O. Smith), Puronics (Franklin Electric), or RainSoft (Pentair). Clack also runs a separate blow-molding plastics division alongside its water-treatment valve business.
That independence is part of why Clack doesn’t show up on Amazon the way Fleck-valve systems do. Clack sells its valves and complete OEM systems to a network of independent assemblers and dealers — the same role Pentair plays for Fleck — but without the same volume of assemblers choosing to list finished Clack-valve systems on general online marketplaces. One specialty water-treatment retailer’s own buying guide puts it plainly: Clack has become harder to source through online dealers in recent years because of distribution restrictions. Plumbing-supply wholesalers like Pace Supply carry the full WS1 lineup, from an 8 GPM, 24,000-grain unit up to a 20 GPM, 75,000 grain unit, but pricing on those listings requires a trade login — not a published consumer price.
Clack WS1 Digital Metered Control Valve
- What you'll find searching Amazon for "Clack WS1" is inconsistent — sometimes a replacement bypass valve or control-board part, rarely a complete softener system with a published price.
- If you want a genuine WS1-valve system with a clear retail price, specialty water-treatment dealers and sites like Aquatell and U.S. Water Systems carry complete units, typically in the $1,200-$2,500 range once a resin tank and brine tank are included.
- A trade-login wholesale account at a plumbing distributor like Pace Supply carries the full WS1 size range, but that channel is built for contractors, not a one-time homeowner purchase.
A bigger household with high peak-flow demand is exactly the situation where the Clack-vs-Fleck gap stops being theoretical — Amazon Prime at least means that whichever valve-based system you land on, replacement cartridges and parts that are actually stocked online ship free in two days instead of adding a dealer’s lead time on top of a backorder. Try it free for 30 days.
Fleck 5600SXT 48,000-Grain System (the Amazon-buyable alternative)
- If a published Amazon price and a DIY install matter more than the extra flow rate, this is the practical answer to "how do I actually buy one of these valves today" — our full Fleck water softener review breaks down sizing and which assembler to buy from.
- Lower upfront cost than a dealer-installed Clack system, and parts (seals, O-rings, the digital SXT board) are stocked by dozens of independent suppliers rather than one dealer network.
- For most single-family homes under roughly 5 people, the 5600SXT's lower flow ceiling isn't the limiting factor — household fixture count and simultaneous-use habits usually hit a wall before 19-21 GPM does.
Bottom line
Clack isn’t a lesser valve than Fleck — on flow rate and maximum tank size, the numbers dealers quote put it ahead. What it isn’t is an easy online purchase: Clack Corporation’s OEM-and-dealer distribution model means a complete WS1 system usually costs more and takes a dealer relationship to get, while a Fleck 5600SXT-based system from an online assembler is a same-day Amazon decision at a lower price. If you’re sizing a softener for a large household and already talking to a local water-treatment dealer, it’s worth asking whether the quoted unit runs a genuine Clack WS1 valve — the throughput advantage is real. If you’re buying online without a dealer in the picture, our best water softener picks, built around Fleck-valve systems, remain the simpler path.