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Fleck 2900 vs 2900s: What Changed, and Which Parts Interchange
If you're shopping for a 2" commercial softener or filter valve, or you've got an older Fleck 2900 on a tank and need parts, the "s" matters. The Fleck 2900s is the current version of Pentair's 2" control valve; the original 2900 is the design it replaced. They look alike, mount on the same tanks and are rated for the same flow, but they are not the same valve and most of their internals don't interchange. Here's what actually changed and what it means for you.
Fleck 2900 vs 2900s at a glance
| Spec | Fleck 2900 (original) | Fleck 2900s (current) |
|---|---|---|
| Status | Discontinued; parts still available | In production |
| Inlet / outlet | 2" | 2" |
| Valve body | Solid brass | Lead-free brass (meets the Safe Drinking Water Act definition and California Prop 65) |
| Piston design | Upper and lower piston | Two hydraulically balanced pistons that independently pilot service flow and regeneration |
| Continuous flow (15 psi drop) | 106 GPM | 106 GPM |
| Peak flow (25 psi drop) | 140 GPM | 140 GPM |
| Max backwash (25 psi drop) | 36 GPM | 36 GPM |
| Tank sizes | Softeners to about 30", filters to 36" | Softeners 14–36", filters 14–30" |
| Regeneration | Downflow; upflow optional | Downflow or upflow, 5 adjustable cycles |
| Controllers | Electromechanical timer; SXT / NXT retrofits on later units | Electromechanical, XT, 3200NXT, 3214NXT (NXT2) |
| Brine systems | 1600 / 1700 | 1600, 1650, 1700, 1710 (1710 upflow brine valve is 2900s-only) |
| Seal & spacer kit | 60128 | 61530 |
| Working pressure / temp | 20–125 psi, 34–110°F | 20–125 psi, 34–110°F; hot-water versions to 150–180°F |
What Pentair changed with the 2900s
Lead-free brass
The biggest reason the 2900s exists. Federal lead-free plumbing rules tightened in 2014 to a 0.25% weighted lead limit on wetted surfaces, and the original 2900's brass body didn't meet it. The 2900s body is cast in lead-free brass and certified by the WQA to NSF/ANSI 61 Section 8 (material safety) and Annex G. If you're installing on potable water in a commercial building today, this alone rules out a new-old-stock 2900.
Redesigned pistons and seals
The 2900s uses two hydraulically balanced pistons: one pilots service flow, the other pilots regeneration, and each is balanced so line pressure isn't fighting the drive motor. The original 2900 also had an upper and lower piston, but the geometry, the seals and spacers, and the piston assemblies were all redone. That's why the seal and spacer kits carry different part numbers (60128 for the 2900, 61530 for the 2900s) and why a 2900s piston won't drop into a 2900 body.
Same flow, same footprint
Pentair kept the numbers that matter for sizing: 106 GPM continuous at 15 psi drop, 140 GPM peak, 36 GPM backwash, 2" inlet and outlet, 4"-8 UN tank thread, 1.5" distributor pilot, 1" NPT drain. A 2900s replaces a 2900 on the same tank without re-plumbing; it's a swap, not a rebuild.
Modern controllers
The 2900s ships with the electromechanical timer, the XT digital timer, or the 3200NXT / 3214NXT (NXT2) network controllers, which link multiple valves over CAT5 for duplex, triplex and progressive-flow systems. Many original 2900s in the field are still on the mechanical 7- or 12-day timer; some later ones were fitted with SXT or NXT heads. Powerhead-level parts (motors, some switches, timers) are shared across the 2750 / 2850 / 2900 family, which is why an old 2900 is still serviceable.
Which parts interchange, and which don't
- Don't interchange: valve body, pistons, seal & spacer kits, the 1710 upflow brine valve, and the downflow/upflow internals. Order by "2900" or "2900s" and by serial date; the wrong seal kit is the most common wasted order on these valves.
- Usually interchange: 24 V drive motors, environmental covers, meters (2" brass, stainless or plastic), 2300/2310/2350 safety brine valves, 1600/1700-series brine tanks and float assemblies, and the tank adapter thread.
- Not sure which you have? The 2900s body is stamped 2900s and is lead-free marked; the service manual parts list for the 2900s shows body part 41428-xx. If your valve predates about 2009 it's an original 2900.
Should you replace a 2900 with a 2900s?
If the old valve is working and it's on non-potable process water, rebuild it; seal kits and pistons for the original 2900 are still sold. If it's on potable water in a commercial or institutional building, the lead-free requirement decides it: replace with a 2900s at the next rebuild. And if you're spec'ing a new system, there is no decision to make: every new 2" Fleck softener or filter, including our Fleck 2900 2" commercial water softener, ships on the 2900s valve, usually with a 1700 brine system and an NXT2 controller.
Sizing note. 106 GPM continuous is the valve's rating, not the softener's. The softener's real service flow is set by resin volume and tank diameter (about 10 GPM per cubic foot of resin at 15 psi drop for good hardness leakage); a 2900s on a 14" tank won't deliver 106 GPM of soft water. Size the tank first, then confirm the valve. We do this for free from your peak flow, hardness and hours of operation: call 800-374-2143.
Fleck 2900s quick specs
- Lead-free brass body, 2" inlet/outlet, 5-cycle, downflow or upflow
- 106 GPM continuous, 140 GPM peak, 36 GPM backwash, Cv 27.5
- Meter range 3–150 GPM ±5%; capacity 1,250–21,250 gal mechanical, to 9.9 million gal on XT/NXT
- 24 V, 110 V or 220 V, 50/60 Hz; 300 psi hydrostatic, 20–125 psi working
- Options: no-hard-water-bypass, service valve operator, auxiliary switches, side mount, treated-water regeneration, hot-water to 180°F
See all commercial water softeners on Clack and Fleck 2" valves, or request a quote with your flow and hardness numbers.
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