Industrial water softening and reverse osmosis (RO) systems produce high-purity water for boilers, manufacturing, and process use. Pumps handle raw water, brine (regeneration), and high-pressure RO feed. This guide covers pump selection for water softening, RO, and demineralized water systems.
Water Softening / RO Pump Services
| Service | Fluid | Pressure | Key Characteristic | Pump Type |
|---|---|---|---|---|
| Raw water feed (to softener/RO pre-treatment) | Raw water (municipal/well) | 2โ5 bar | Clean-ish, large flow, continuous, low pressure, some sediment | Horizontal split case or end-suction centrifugal (cast iron/bronze, large flow, low head) |
| Multimedia filtration feed | Raw water (to sand/anthracite filter) | 2โ5 bar | Clean-ish, large flow, continuous, backwash capability | End-suction centrifugal or split case (large flow, low head, cast iron/bronze) |
| Carbon filtration feed | Water (to activated carbon filter) | 2โ5 bar | Clean, large flow, continuous, chlorine removal | End-suction centrifugal (cast iron/316SS, large flow, low head) |
| Water softener feed | Water (to ion exchange softener) | 2โ5 bar | Clean, large flow, continuous, low pressure | End-suction centrifugal (cast iron/bronze/316SS, large flow, low head) |
| Brine (regeneration) | Sodium chloride solution (10โ25% NaCl) | 1โ3 bar | Corrosive (chloride), viscous (25% ~3 cP), precise (regeneration dose), intermittent, crystallizes (cold) | 316SS/duplex centrifugal or peristaltic (corrosion, precise, intermittent, EPDM/PTFE) |
| Brine injection (venturi) | Brine (to eductor/venturi) | 2โ5 bar | Corrosive, precise, small flow, intermittent | Diaphragm metering or peristaltic (PTFE/EPDM, precise, corrosive) |
| RO feed pump (to RO membranes) | Pre-treated water (to RO) | 5โ15 bar (feed) | Very clean (5 ฮผm filtered), moderate flow, continuous, low-NPSH (some), critical (RO performance) | 316SS centrifugal or API 610 OH2 (316SS, clean, moderate pressure, low-NPSH) |
| RO high-pressure pump | Pre-treated water (to RO membranes) | 10โ80 bar (brackish 10โ30 bar, seawater 50โ80 bar) | Very clean (1โ5 ฮผm filtered + carbon), high pressure, moderate flow, continuous, critical (RO pressure = performance), energy recovery (seawater) | Multistage centrifugal (316SS/duplex, high pressure, clean, high efficiency) or positive displacement (plunger) for very high pressure |
| RO permeate (product water) | RO permeate (deionized water) | 1โ3 bar | Very clean, low conductivity (corrosive to carbon steel), moderate flow, continuous, valuable | 316SS centrifugal (316SS ONLY โ carbon steel corrodes in DI water, clean, large flow) |
| RO concentrate (reject) | RO concentrate (high TDS) | 10โ70 bar | Corrosive (high chloride/salts), scaling (CaCO3, CaSO4, silica), moderate flow, continuous, environmental (disposal) | 316SS/duplex centrifugal (corrosion, high pressure, scaling-resistant) or energy recovery device (seawater) |
| Demineralized (DI) water transfer | DI water (mixed bed product) | 2โ5 bar | Very clean, very low conductivity (๏ผ1 ฮผS/cm), corrosive to carbon steel, large flow, continuous, critical (boiler feed) | 316SS centrifugal (316SS ONLY, electropolished, clean, large flow) โ NOT carbon steel |
| Boiler feed water (BFW) | High-purity BFW (to boiler) | 20โ100 bar | Very clean, hot (100โ150ยฐC), high pressure, large flow, critical (boiler), low-NPSH, deaerated | API 610 BB3 multistage (316SS, high pressure, high temp, BFW quality, low-NPSH) |
| Antiscalant dosing | Antiscalant (polyphosphonate, etc.) | โ | Corrosive (some), viscous (some), precise (RO scaling prevention), small flow, continuous | Diaphragm metering (PTFE, precise, zero leakage, corrosive) |
| pH adjustment (acid/base) | H2SO4, HCl, NaOH | โ | Corrosive, precise (RO pH control ๏ผ7.5), small flow, continuous | Diaphragm metering (PTFE, precise, zero leakage, corrosive) |
| Disinfectant (chlorine/bisulfite) | NaOCl (chlorine) or NaHSO3 (bisulfite โ dechlorination) | โ | Corrosive (oxidizer), precise, small flow, continuous, safety (chlorine toxic) | Diaphragm metering (PTFE, precise, zero leakage, corrosive oxidizer) |
| Clean-in-place (CIP) for RO | Citric acid (pH 2) or NaOH (pH 12) + surfactant | 2โ5 bar | Corrosive (acid/base), hot (35โ45ยฐC), intermittent, precise, membrane cleaning | 316SS centrifugal or peristaltic (corrosion, intermittent, CIP-compatible) |
| Backwash (filter backwash) | Clean water (reverse flow through filter) | 2โ5 bar | Large flow, intermittent, high flow rate (10โ20 L/mยฒ/s), low head | Horizontal split case or large end-suction (large flow, low head, cast iron/bronze) |
Critical: RO High-Pressure Pump (10โ80 bar) + Energy Efficiency
The RO high-pressure pump is the heart of the system โ pressure determines RO performance and energy cost:
- High pressure: Brackish water RO: 10โ30 bar. Seawater RO: 50โ80 bar. Use multistage centrifugal pump (3โ8 stages, 316SS or duplex for seawater). High efficiency (80โ85%) โ energy is 30โ50% of RO operating cost. Variable speed drive (VSD) for pressure/flow control. Positive displacement (plunger) for very high pressure/small flow. Our high-efficiency multistage range handles RO high pressure.
- Very clean feed: RO membranes require 1โ5 ฮผm filtration + carbon (chlorine removal โ chlorine damages thin-film membranes). High-pressure pump must handle clean water (no abrasives). 316SS (corrosion from concentrate). Low-NPSH (some RO systems have low feed pressure). Our clean-water multistage pumps handle RO feed.
- Energy recovery (seawater): Seawater RO concentrate at 50โ70 bar contains significant energy โ use energy recovery device (PX pressure exchanger or turbocharger) to reduce energy 30โ50%. High-pressure pump + energy recovery = optimized system. Our seawater RO systems include energy recovery.
Critical: DI / RO Permeate Corrosion (Low Conductivity)
- DI water corrosion: Deionized water (๏ผ1 ฮผS/cm) is highly corrosive to carbon steel (leaches iron โ contaminates water). Use 316SS (minimum) or higher alloy (duplex, titanium for ultrapure). Electropolished surfaces (reduce leaching, easier cleaning). NO carbon steel, NO cast iron (iron contamination). Plastic (PVC, PVDF) for low pressure. Our 316SS/electropolished range handles DI water.
- RO permeate: RO permeate (10โ50 ฮผS/cm) is less corrosive than DI but still attacks carbon steel. Use 316SS. Large flow transfer. Our 316SS centrifugal range handles RO permeate.
- BFW: Boiler feed water must be very pure (dissolved oxygen ๏ผ7 ppb, silica ๏ผ20 ppb). 316SS or duplex. High pressure (20โ100 bar) + high temp (100โ150ยฐC). Deaerated (low NPSH โ use low-NPSH pump, flooded suction from deaerator). API 610 BB3 multistage standard for BFW. Our high-pressure multistage range handles BFW.
Critical: Brine (Softener Regeneration) + Corrosion
- Brine corrosion: 10โ25% NaCl brine is corrosive (chloride pitting). Use 316SS (dilute, ambient) or duplex (concentrated, higher temp). PTFE/EPDM seals (NOT NBR โ brine OK but check). Peristaltic (EPDM hose) for small/intermittent. Brine crystallizes below ~0ยฐC (25% NaCl) โ keep above 5ยฐC, jacket if needed. Our corrosion-resistant range handles brine.
- Precise regeneration: Softener regeneration requires precise brine dose (5โ10% NaCl at 2โ4 gpm per ftยณ resin). Use diaphragm metering or peristaltic (precise, intermittent). Brine eductor (venturi) with brine pump. Calibration. Our metering/peristaltic range handles brine regeneration.
Critical: Chemical Dosing (Antiscalant, pH, Disinfectant)
- Antiscalant: RO membranes scale (CaCO3, CaSO4, BaSO4, silica). Antiscalant (polyphosphonate, polyacrylate) dosing 2โ5 mg/L. Use PTFE diaphragm metering (precise, zero leakage, corrosive). Multiple pumps (one per chemical). Calibration. Pulsation dampener. Our metering range handles antiscalant.
- pH adjustment: RO feed pH ๏ผ7.5 (reduce CaCO3 scaling, but ๏ผ4 to avoid membrane damage). Acid (H2SO4/HCl) or base (NaOH). PTFE diaphragm metering. pH probe feedback. Safety (acid-base). Our metering range handles pH control.
- Disinfectant / dechlorination: Chlorine (NaOCl) for pre-treatment disinfection; sodium bisulfite (NaHSO3) to remove chlorine before RO (chlorine damages membranes). PTFE diaphragm metering (corrosive oxidizer). ORP probe (monitor chlorine residual ๏ผ0.1 ppm before RO). Safety (chlorine toxic). Our metering range handles disinfectant.
Critical: CIP for RO Membranes
- RO CIP: Membranes foul (biological, organic, inorganic scale). CIP with: acid (citric, pH 2 โ removes scale), base (NaOH + surfactant, pH 12 โ removes organic/bio). Temperature 35โ45ยฐC (warm improves cleaning). Flow rate 6โ10 mยณ/h per 8" vessel. Use 316SS centrifugal or peristaltic (corrosion, intermittent). CIP tank + heater + pump. Flush with permeate after CIP. Our CIP systems clean RO membranes.
Material Compatibility
| Material | Raw water (ambient, clean-ish) | Brine 25% NaCl (ambient, corrosive) | RO feed (clean, 5 ฮผm) | DI water (ambient, ๏ผ1 ฮผS/cm) | RO concentrate (seawater, 70 bar, corrosive) | CIP acid (pH 2, 40ยฐC) |
|---|---|---|---|---|---|---|
| Cast iron | Good (standard) | NOT (chloride pitting) | Fair (rust contamination) | NOT (DI corrosion) | NOT | NOT (acid) |
| Bronze | Good (water, standard) | Fair (chloride, check) | Good | Fair (copper leaching) | NOT (seawater pitting) | NOT (acid) |
| Carbon steel | Fair (rust) | NOT | NOT (iron contamination) | NOT (severe DI corrosion) | NOT | NOT |
| 316SS | Excellent | Good (dilute, ambient) | Excellent | Good (minimum for DI) | Fair (seawater pitting risk) | Good (dilute acid, 40ยฐC) |
| Duplex SS | Excellent | Excellent (concentrated brine) | Excellent | Excellent | Excellent (seawater, PREN ๏ผ40) | Good |
| Super duplex | Excellent | Excellent | Excellent | Excellent | Excellent (seawater RO) | Excellent |
| Titanium | Excellent | Excellent | Excellent | Excellent (ultrapure) | Excellent (seawater, best) | Excellent |
| PTFE-lined | Good | Excellent | Fair (not for high pressure) | Good (low pressure) | NOT (high pressure) | Excellent |
| EPDM seals | Excellent (water) | Good (brine) | Excellent | Excellent | Good (seawater) | Good (dilute acid) |
| NBR seals | Good (water) | Good (brine) | Good | Good | Fair | NOT (acid) |
| PTFE seals | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Critical: Raw water = cast iron/bronze (low pressure, large flow). Brine = 316SS/duplex + EPDM/PTFE (NOT cast iron/bronze for concentrated). RO feed = 316SS (clean, moderate pressure). RO high pressure = 316SS/duplex/super duplex multistage (10โ80 bar, high efficiency). DI/permeate = 316SS minimum (NOT carbon steel/cast iron โ corrosion/contamination). Seawater concentrate = duplex/super duplex/titanium (chloride pitting). CIP = 316SS/peristaltic + EPDM/PTFE. Chemical dosing = PTFE diaphragm metering (all corrosives). All = filtration (protect membranes/pump) + material compatibility + energy efficiency (RO high pressure).
Common Problems and Solutions
Problem 1: RO permeate has iron (carbon steel pump). Carbon steel pump corrodes in DI/RO water โ iron contamination. Solution: use 316SS centrifugal (minimum). Electropolished. NO carbon steel. Our 316SS range prevents iron contamination.
Problem 2: RO high-pressure pump inefficient (energy cost). Low-efficiency pump = high energy cost. Solution: use high-efficiency multistage centrifugal (80โ85% efficiency). VSD. Energy recovery (seawater). Our high-efficiency multistage reduces energy cost.
Problem 3: Brine pump corrodes (cast iron). 25% NaCl corrodes cast iron/bronze. Solution: use 316SS/duplex centrifugal or peristaltic (EPDM hose). EPDM/PTFE seals. Our corrosion-resistant range handles brine.
Problem 4: RO membranes foul (no antiscalant). CaCO3/CaSO4 scale damages membranes. Solution: antiscalant dosing via PTFE diaphragm metering. pH control ๏ผ7.5. CIP (acid/base). Monitor LSI/S&DSI. Our dosing systems prevent scaling.
Problem 5: Chlorine damages RO membranes (no bisulfite). Chlorine in feed oxidizes thin-film membranes. Solution: sodium bisulfite dosing (metering pump) + ORP monitor (๏ผ0.1 ppm). Carbon filter. Our dechlorination systems protect membranes.
Selection Summary
- Raw water/filtration feed: Horizontal split case or end-suction (cast iron/bronze, large flow, 2โ5 bar, low head)
- Softener feed: End-suction centrifugal (cast iron/bronze/316SS, large flow, 2โ5 bar)
- Brine regeneration: 316SS/duplex centrifugal or peristaltic (10โ25% NaCl, corrosion, precise, intermittent, EPDM/PTFE)
- RO feed pump: 316SS centrifugal or OH2 (very clean, 5โ15 bar, moderate flow, low-NPSH)
- RO high-pressure: Multistage centrifugal (316SS/duplex, 10โ30 bar brackish / 50โ80 bar seawater, high efficiency, VSD, energy recovery)
- RO permeate/DI water: 316SS centrifugal (316SS ONLY, NOT carbon steel, clean, large flow, low conductivity corrosion)
- RO concentrate: 316SS/duplex centrifugal (high TDS, corrosion, scaling, 10โ70 bar) + energy recovery (seawater)
- BFW: API 610 BB3 multistage (316SS, 20โ100 bar, 100โ150ยฐC, deaerated, low-NPSH)
- Antiscalant/pH/disinfectant: PTFE diaphragm metering (precise, zero leakage, corrosive, multiple pumps)
- CIP: 316SS centrifugal or peristaltic (acid/base, 35โ45ยฐC, intermittent, membrane cleaning)
- Backwash: Horizontal split case (large flow, low head, intermittent, cast iron/bronze)
- Critical: RO high pressure = multistage (10โ80 bar) + high efficiency + VSD + energy recovery (seawater), DI/permeate = 316SS ONLY (NOT carbon steel โ DI corrosion + iron contamination), brine = 316SS/duplex + EPDM (NOT cast iron/bronze), seawater = duplex/super duplex/titanium (chloride pitting), chemical dosing = PTFE metering (antiscalant/pH/disinfectant), all = filtration (5 ฮผm pre-RO, 1โ5 ฮผm high-pressure) + material compatibility + energy efficiency
- Our multistage covers RO high pressure/BFW; 316SS centrifugal covers feed/permeate/DI; split case covers raw water; metering covers chemicals; peristaltic covers brine/CIP. For water treatment pump selection, talk to our water engineers with your feed water quality, RO capacity, and permeate quality requirements.