Fleck 5600SXT vs 5800 vs Clack WS1 valves, and what replaced the 7000

For a typical home softener with 1 to 1.5 ft³ of resin, the Fleck 5600SXT and the Fleck 5800 deliver about the same flow in practice, because the resin tank limits flow long before either valve does. The real difference is backwash: Pentair rates the 5800SXT at 17 gpm and softener tanks up to 16 inches, against 7 gpm and 12 inches for the 5600SXT. The Clack WS1 goes further (27 gpm, tanks up to 21 inches) with a screwless design. The Fleck 7000SXT is discontinued, and dealers sell the 5810SXT in its place.

Every figure below comes from the makers’ own documents: Pentair’s 5600SXT spec sheet (a Pentair sheet hosted by a dealer), Pentair’s 5800 spec sheet and 5800SXT service manual, and Clack’s WS1 spec sheet and WS1 manual. We research from these documents and haven’t installed any of the three valves.

Fleck 5600SXT vs 5800 and Clack WS1 spec sheets side by side

The Fleck and Clack flow figures are not measured the same way. Pentair rates the valve alone, and Clack rates the WS1 with its bypass and meter in the water path. The extra parts add restriction, so Clack’s 27 gpm comes from the harder test. The Fleck meter ranges are for the 3/4 in paddle or turbine meter both Pentair sheets list.

One figure differs between seller and maker. AFW Filters lists 28 gpm peak for its 5600SXT 48,000-grain system, while Pentair’s spec sheet gives the valve 26 gpm peak at a 25 psi drop. We use Pentair’s number. The 2 gpm gap won’t matter in a home, for the reason explained under why the tank limits flow.

Where the Clack WS1 differs from Fleck

Service design. Pentair describes both Fleck valves as using a hydraulically balanced piston, and the 5800SXT manual sells the piston and its seals as one kit. The Clack WS1 uses a piston that moves in a straight line through a one-piece seal and spacer stack. Its manual says the valve has no traditional fasteners: clips, threaded caps and snap latches hold it together, and the caps only need hand-tightening because they use radial seals. Clack lists the tools as two screwdrivers and a pair of pliers, or its plastic service wrench.

Downflow and upflow are set at the factory. All three valves come in downflow and upflow versions. The Clack manual advises against converting a WS1 between the two in the field, because the valve bodies differ and a mismatched body and piston lets hard water bypass the resin. The 5800SXT manual lists separate downflow and upflow piston and seal kits. Decide the regeneration direction before you buy.

Programming. The Fleck SXT controller has a short user program (hardness, regeneration time, day override, reserve) and a master program, which the 5800SXT manual opens by setting the clock to 12:01 PM. The manual asks you to contact a dealer before changing master settings. Clack writes its WS1 manual for system builders (OEMs), who set capacity and cycle times at the factory. The builder can lock everything except hardness, day override, regeneration time and time of day, though the unlock key sequence is printed in the same manual. Our Fleck 5600SXT settings guide goes through the SXT screens one by one.

Brine refill and backwash. A downflow Clack softener always runs two backwashes, and it refills the brine tank with treated water, either after the rinse or as a pre-fill two hours before regeneration. Pentair lists double backwash and soft water refill as 5800 features. For the 5600, double backwash is an optional cam.

Parts. Both makers publish parts breakdowns. The 5800SXT manual lists part numbers down to the brine line flow control, and Clack points to a separate WS1 drawings and service manual. A parts seller can match a worn seal kit or piston by number on either brand.

Why the tank limits flow before the valve does

The resin bed sets the flow a softener can soften properly. The design guide published in Water Conditioning & Purification magazine uses 5 gpm per cubic foot of resin for continuous flow and 7.5 gpm per cubic foot for peak flow:

Every valve here is rated at 20 gpm or more of continuous flow, roughly three times what a 1.5 ft³ bed can treat at the design rate. Swapping a 5600SXT for a 5800SXT on the same tank doesn’t raise the flow your showers get. Even sellers’ own ratings, such as AFW’s 12 gpm service flow for its 1.5 ft³ build, stay well below the valve. If you’re choosing a size, our water softener size calculator works out the resin volume first and checks the flow against it, and our guide to water softener grain capacity explains what the grain rating on each tank size means.

Backwash is where the valve matters. Backwash flow has to scale with the tank’s cross-section, and Pentair sizes filter tanks at 10 gpm per square foot. A 10 in tank has about 0.55 ft² of bed area and needs about 5.5 gpm. A 12 in tank has about 0.79 ft² and needs about 7.9 gpm, more than the 5600’s 7 gpm maximum. That is why the 5600 spec sheet stops filters at 10 inches.

Softener resin needs less. The WC&P guide gives 4.2 gpm per square foot at 50°F and 6.7 gpm at 77°F, so a 12 in softener tank needs about 5.3 gpm even in warm water. That fits within 7 gpm, and it’s why the 5600 covers softener tanks up to 12 inches. Pentair’s filter figure is higher than either, so for a filter, or a softener tank above 12 inches, the 5800 or the Clack is the valve to look at. Our guide to the best iron filters for well water lists each filter’s backwash demand.

Two practical checks follow. The actual backwash rate is set by the drain line flow control fitted to the valve, and the 5800SXT manual lists these from 8 to 15 gpm. The manual also calls for a 3/4 in drain line above 7 gpm or on runs over 20 feet. On a well, your pump has to deliver that backwash rate as well as the house.

What replaced the Fleck 7000SXT

The Fleck 7000SXT is gone. Discount Water Softeners reports that Pentair discontinued the 7000 and 5000 valves on September 30, 2016, with service parts for about five more years. We didn’t find a notice from Pentair itself, so this rests on dealer notices. Dealers such as Glass Water Systems now list the Fleck 5810SXT as the replacement.

The 5810 is the larger sibling of the 5800. Pentair’s 5810 spec sheet gives it 36 gpm continuous and 47 gpm peak with the downflow piston, 28 gpm of backwash, connections up to 1-1/4 in and tanks up to 21 inches. So “Fleck 5600SXT or 5810SXT” is really a question about plumbing size and tank size.

Much of the forum advice comparing the 5600SXT with the 7000SXT predates 2016. Read “7000” in those threads as “5810” and the reasoning mostly still holds, since the point was usually larger pipes and tanks. If a listing still sells a 7000SXT, ask where its parts will come from.

Which valve to choose

The only complete valve-plus-tank system we list is AFW Filters’ 5600SXT build: a metered valve on a 10 x 54 tank with 1.5 ft³ of 8% crosslink resin. It was in stock when we checked on September 27, 2026, and our Fleck 5600SXT review covers that build in detail. Its downsides are real: AFW doesn’t publish a maximum iron figure, and several well-water softeners use 10% crosslink resin instead of 8%.

AFW Filters

Fleck 5600SXT 48,000-grain softener (AFW Filters build)

A Pentair Fleck 5600SXT metered valve on a 10 x 54 tank with 1.5 ft³ of 8% crosslink resin, sold as a complete system by AFW Filters. The valve is common and widely serviced; the iron limit is not published.

Best for Buyers who want a standard metered Fleck valve and plan to set it up themselves

Check price atAFW Filters (opens AFW Filters site)

Photo: AFW Filters

Who should skip all three

A bare valve choice assumes your water only needs softening. If your well test shows iron above a few parts per million, or a rotten-egg smell, the valve is the smaller question. Start with our guide to choosing between an iron filter and a water softener, because the order and type of equipment matter more than the valve brand.

If you’d rather not program a valve and would like one company to answer for the whole system, a packaged softener with published iron and flow limits is the easier path. Our roundup of the best water softeners for well water compares those limits, and the SpringWell vs SoftPro comparison covers two brands that sell direct online. Whichever valve you pick, salt and water use depend on the salt setting you program, not the brand, and our running cost calculator shows what that setting costs a year. More softener guides are on the water softeners hub.