RO Membrane Cleaning Chemicals and CIP Procedure: 10 Cleaners, pH Limits and Steps

RO membrane cleaning chemicals are high-pH cleaners, such as caustic soda with a detergent or EDTA, and low-pH cleaners, such as hydrochloric or citric acid, that are recirculated off-line through reverse osmosis and nanofiltration elements once normalized permeate flow has fallen about 10 %. Which cleaner removes which foulant, how hot and how alkaline may the solution get, and when is a train past saving? Two element makers' documents, DuPont FilmTec Form 45-D01696 and Hydranautics TSB107, answer with numbers.

Membrane cleaners are the off-line members of the water treatment chemicals used in an RO plant: antiscalants and biocides are dosed into the feed, while cleaners are mixed in a separate tank and flushed out before service.

The four figures that frame an RO cleaning program are listed below.

• 10 % drop in normalized permeate flow: the cleaning trigger of Form 45-D01696.
• 3 to 12 months: the typical cleaning interval (TSB107).
• pH 1 to 12 at up to 35 °C (95 °F): the cleaning envelope of FilmTec brackish and seawater RO elements.
• 982 product-function rows: NSF/ANSI/CAN 60 Membrane Cleaner listings (NSF listings, 2026-10-21).

Every value on this page is checked against primary sources; see our methodology and fact-checking process.

What Are RO Membrane Cleaning Chemicals and When Does a Membrane Need Cleaning?#

An RO membrane cleaner is an off-line chemical solution that dissolves or lifts scale, metal oxides, organics and biofilm so that the element again rejects 95 to more than 99 % of dissolved salts at its design pressure. High-pH cleaners remove organics and biofilm, low-pH cleaners remove scale and metal oxides. Polyamide tolerates less than 0.1 mg/L (ppm) free chlorine, so bleach cleans are excluded. At what loss of performance should cleaning start?

Which Cleaning Triggers Do Membrane Makers Set?#

DuPont FilmTec triggers a cleaning when normalized permeate flow drops 10 %, normalized salt passage rises 5 to 10 % or normalized pressure drop rises 10 to 15 % against the reference taken after start-up or the last cleaning. Three sources set the cleaning trigger at similar values, and the table compares them.

The EPA values come from its 2005 Membrane Filtration Guidance Manual for NF and RO. Normalization follows ASTM D4516-19a, so a clogged membrane shows as a trend, not one cold-day reading.

How Often Are RO Membranes Cleaned, and When Is Cleaning Too Late?#

RO membranes are typically cleaned once every 3 to 12 months, and Hydranautics treats more than one cleaning per month as a sign that pretreatment needs an upgrade. The EPA manual gives 3 months to 1 year for NF and RO.

Once normalized performance has dropped 30 to 50 %, full restoration may be impossible (TSB107), and a doubled pressure drop or a 50 % loss of normalized product flow is the emergency condition of Form 45-D01504.

Which 10 Chemicals Are Used as RO Membrane Cleaners?#

The 10 chemicals used to clean RO membranes are 4 high-pH ingredients (sodium hydroxide, sodium dodecyl sulfate, EDTA and sodium tripolyphosphate), 4 acids (hydrochloric, citric, phosphoric and sulfamic acid), 1 reducing cleaner (sodium hydrosulfite) and 1 biocide used inside the cleaning sequence (DBNPA).

Recipes come from DuPont FilmTec Form 45-D01696 (wt %) and Hydranautics TSB107 (per 379 L, or 100 US gal, of make-up water). The table lists each cleaning chemical with the foulant it targets, the published recipe and its limit.

Recipes are cleaning-solution strengths, never feedwater doses.

1. Sodium Hydroxide (Caustic Soda): The Base of High-pH Cleaners#

Sodium hydroxide (caustic soda, CAS 1310-73-2) is the base of every high-pH RO cleaner: Form 45-D01696 cleans at 0.1 wt % NaOH, pH 12 and no more than 35 °C (95 °F), alone or with 0.025 wt % SLS or 1.0 wt % Na4EDTA. TSB107 runs 0.1 % (w) at pH 11.5 and 30 °C (86 °F) and uses caustic alone for polymerized silica.

2. Sodium Dodecyl Sulfate (SLS): The Detergent for Organics and Biofilm#

Sodium dodecyl sulfate (SLS, Na-DSS, CAS 151-21-3) is the anionic detergent of high-pH RO cleaners, used at 0.025 wt % with 0.1 wt % NaOH at pH 12 (Form 45-D01696) or at 0.03 % (w) and pH 11.5 (TSB107). SLS can precipitate in cold solution, so cleaning never runs below 20 °C (68 °F), and the flush water is checked for foam.

3. EDTA: The Chelant for Sulfate Scale and Gel Foulants#

EDTA, used as its tetrasodium salt Na4EDTA (CAS 64-02-8; EDTA acid 60-00-4), is the preferred chelant of Form 45-D01696 for calcium and barium sulfate scale, at 1.0 wt % with 0.1 wt % NaOH, pH 12 and no more than 35 °C (95 °F). Repeated alkaline EDTA cleaning also removes antiscalant gel.

EDTA has no NSF/ANSI/CAN 60 chemical category; EDTA cleaners are certified as proprietary products. EDTA, GLDA and gluconate are compared as chelating agents across boilers and cleaning.

4. Sodium Tripolyphosphate (STPP): The Builder in High-pH Chelant Cleaners#

Sodium tripolyphosphate (STPP) is the builder in the high-pH chelant cleaners of TSB107 for calcium sulfate scale and natural organic matter: 2.0 % (w), 7.7 kg (17.0 lb) per 379 L (100 US gal), with 0.8 % Na-EDTA, 3.18 kg (7.0 lb), or 0.025 % sodium dodecylbenzene sulfonate, at pH 10.0 and 40 °C (104 °F). The pH is adjusted with hydrochloric acid, never with sulfuric acid.

5. Hydrochloric Acid: The Standard Low-pH Cleaner for Carbonate Scale#

Hydrochloric acid is the preferred low-pH cleaner of Form 45-D01696 for calcium carbonate scale, at 0.2 wt %, pH 1 to 2 and 25 °C (77 °F), while TSB107 uses a harsher 0.5 % (w) of 36 % (22 °Bé) acid at pH 2.5 and 35 °C (95 °F). As a worked example from molar masses, 1 kg of calcium carbonate consumes 0.73 kg of 100 % HCl, about 2.3 kg of 32 % acid.

6. Citric Acid: The Milder Acid for Carbonate and Metal Oxides#

Citric acid is the first low-pH cleaner of TSB107, 2.0 % (w) at 40 °C (104 °F) without pH adjustment, for carbonate and sulfate scales, iron, manganese, nickel, copper and zinc oxides, and inorganic colloids. Form 45-D01696 calls it less effective, with a biofouling risk if not rinsed out. NSF/ANSI/CAN 60 lists it as Membrane Cleaner and Well Cleaning Aid, maximum use "NA": 42 companies, 113 products, 174 product-function rows (NSF listings, 2026-10-21).

7. Phosphoric Acid: An Alternative Acid for Carbonate and Iron#

Phosphoric acid is the alternative low-pH cleaner of Form 45-D01696 for calcium carbonate and iron, at 0.5 wt %, pH 1 to 2 and 25 °C (77 °F). NSF lists phosphoric-acid membrane cleaners for off-line use, flushed out before drinking-water service.

8. Sulfamic Acid: The Membrane Acid with Its Own EN Standard#

Sulfamic acid (NH2SO3H, CAS 5329-14-6) is an alternative low-pH cleaner for calcium carbonate and iron in Form 45-D01696, and the only membrane cleaner with its own European product standard, EN 17841:2024 (Antifouling for membranes: sulphamic acid). It consumes 1.94 kg per kg of calcium carbonate (derived). EN 17841 belongs to the CEN family of EN standards for drinking water treatment chemicals.

9. Sodium Hydrosulfite: The Reducing Cleaner for Iron Fouling#

Sodium hydrosulfite (sodium dithionite, Na2S2O4, CAS 7775-14-6) is the reducing cleaner for iron fouling, at 1.0 wt % and pH 5 in Form 45-D01696 and at its natural pH of 4 to 6 and 35 °C (95 °F) in TSB107. Soaks last 2 to 4 hours, and the solution is replaced when its color changes. It is neither sodium bisulfite nor sodium hydrosulfide.

10. DBNPA: The Non-Oxidizing Biocide in the Cleaning Sequence#

DBNPA (2,2-dibromo-3-nitrilopropionamide, CAS 10222-01-2) is the non-oxidizing biocide that TSB107 adds to the permeate flush before and the acid flush after a complex-fouling clean.

DBNPA's kill mechanism and compatibility are compared with other non-oxidizing biocides.

Which Chemicals Must Never Be Used to Clean RO Membranes?#

Four chemicals must never be used to clean polyamide RO membranes: sulfuric acid, cationic surfactants, chlorine and other oxidants, and, except under specialist control, ammonium bifluoride. The 4 exclusions and their reasons are listed below.

• Sulfuric acid: precipitates calcium sulfate (Form 45-D01696).
• Cationic surfactants: cause irreversible fouling (TSB107).
• Free chlorine and other oxidants: polyamide degrades after about 200 to 1,000 ppm-h (Form 45-D01504).
• Ammonium bifluoride: used at some sites for silica, but hazardous and damaging to equipment (TSB107).

Ammonium bifluoride and inhibited acids for metal equipment are covered under descaling and chemical cleaning agents.

How Is an RO Membrane CIP Procedure Designed and Run?#

An RO membrane CIP procedure is designed in 5 decisions: the cleaner sequence from the foulant, the pH and temperature limits of the element, the make-up water, the recirculation and soak steps, and the skid that delivers the flow.

Which Cleaner First? Matching the Cleaning Chemistry to the Foulant#

DuPont FilmTec cleans alkaline first and acid second, and reverses the order only when the foulant is calcium carbonate or iron oxide and hydroxide alone. Hydranautics TSB107 brackets complex-fouling cleans with DBNPA flushes. The table matches each foulant to the cleaner the membrane makers use for it.

Some supplier guides start with acid, but the makers' order stays the default; the best cleaner is the one matched to the foulant. Diagnosis by autopsy and by the position of the fouled elements belongs to membrane fouling.

What pH and Temperature Limits Apply During Membrane Cleaning?#

Form 45-D01696 allows brackish and seawater RO elements cleaning solutions of pH 1 to 13 up to 25 °C (77 °F), pH 1 to 12 up to 35 °C (95 °F) and pH 1 to 10.5 up to 45 °C (113 °F), so the allowed pH band narrows as the solution gets hotter. The table shows the band per element family.

TSB107 limits exposure at these pH limits to 60 minutes below 40 °C (104 °F) and 30 minutes above, and calls pH 4 to 10 gentle and pH 2 to 12 the harshest range. The minimum cleaning temperature is 20 °C (68 °F), or 21 °C (70 °F) in TSB107.

Caustic and acids bought for feed conditioning are the same pH adjustment chemicals, used here at cleaning strength.

Cleaning Solution Make-Up Water and Mixing#

Cleaning solutions are mixed in RO permeate, deionized water or soft water, and TSB107 specifies make-up water with 0 ppm chlorine, pH 6.5 to 7.5 and hardness below 30 ppm as CaCO3. The 9 make-up water limits are listed below.

• Chlorine: 0 ppm
• pH: 6.5 to 7.5
• Hardness: below 30 ppm as CaCO3
• Calcium: below 5 ppm
• Iron: below 0.05 ppm
• Manganese: below 0.02 ppm
• Aluminum: below 0.05 ppm
• SDI15: below 1
• TOC: below 1 ppm

Each recipe is converted on its own basis, wt % or per 379 L, before the tank is filled.

RO CIP Procedure Step by Step#

An RO membrane CIP runs in 8 steps per stage: mix, displace at low flow, recirculate, soak, recirculate at high flow, rinse, repeat with the second cleaner, and flush to drain before service. The 8 CIP steps are listed below.

1. Mix the cleaner in make-up water and heat it within the element limits.
2. Pump it in at low flow, dumping up to the first 20 % returned (TSB107).
3. Recirculate at 91 to 151 L/min (24 to 40 gpm) per 8-inch tube, inlet at most 4 bar (60 psi).
4. Soak for about 1 hour, or 10 to 15 hours for difficult fouling (Form 45-D01696).
5. Recirculate at high flow for 30 to 60 minutes.
6. Rinse until flush conductivity is within 10 to 20 % of the feed (TSB107).
7. Repeat steps 1 to 6 with the second cleaner.
8. Restart and send permeate to drain for at least 30 minutes or until clear (Form 45-D01696).

Each stage takes 4 to 8 hours; Form 45-D01696 prints 6.0 to 10.2 m³/h (30 to 45 gpm) per 8-inch vessel at 1.5 to 4.0 bar (20 to 60 psig).

CIP Skid Sizing: Tank Volume, Flow and Materials#

A CIP tank holds about 34 L (9 US gal) of solution per 8-inch, 40-inch element for normal fouling and 68 L (18 US gal) for heavy fouling, plus piping volume and the 20 % dumped at the start (TSB107).

Worked example: a 60-element train. Inputs: 10 vessels of 6 elements, 34 L (9 US gal) each, piping excluded. Volume: 60 x 34 L = 2,040 L (540 US gal); Form 45-D01696 sizes this tank at 2.1 m³ (550 US gal). Filled with 2,085 L (5.5 x 379 L), it takes 5.5 x 0.38 kg = 2.1 kg (4.6 lb) NaOH for 0.1 %, or 5.5 x 7.7 kg = 42.4 kg (93.5 lb) citric acid for 2.0 % (TSB107 quantities).

The skid uses a polypropylene or FRP tank, a 316 stainless or nonmetallic pump, a 5 to 10 µm cartridge, CPVC valves and about 3 m/s (10 ft/s) pipe velocity (Form 45-D01696).

How Is RO Membrane Cleaning Controlled and Checked?#

RO membrane cleaning is controlled in the tank by pH, temperature and pressure drop, at the end by rinse conductivity and permeate clarity, and afterwards by normalized permeate flow, salt passage and pressure drop.

pH, Temperature and Pressure Drop During Recirculation#

The cleaning pH is checked throughout recirculation and corrected with caustic or acid when it shifts more than 0.5 units (Form 45-D01696). Pressure drop stays below 1 bar (15 psi) per element and 3.5 bar (50 psi) per multi-element vessel.

Rinse End Points and Return to Service#

Rinsing ends when flush water conductivity is within 10 to 20 % of the feed, after 15 to 60 minutes (TSB107), and the restarted train sends permeate to drain for at least 30 minutes or until clear (Form 45-D01696). After citric acid, rinsing continues until influent and effluent pH match (NSF listing footnote).

Normalized Data Before and After Cleaning#

Cleaning success is judged on normalized data, permeate flow, salt passage and pressure drop corrected to reference conditions by the method of ASTM D4516-19a, compared with the values recorded after start-up or after the last cleaning. Because the triggers are measured against the reference after the last cleaning, the post-clean values become the baseline for the next 10 % flow trigger.

What Goes Wrong in RO Membrane Cleaning?#

RO membrane cleaning fails in 4 ways: it starts too late or in the wrong order, it precipitates new scale, it meets a foulant the standard cleaners cannot dissolve, or it leaves residue that feeds biofilm.

Cleaning Too Late or in the Wrong Order#

A train cleaned after normalized performance has dropped 30 to 50 % may never be fully restored (Hydranautics TSB107), and sulfate scale older than one week is rarely removable (DuPont Form 45-D01696).

Precipitates from Cold Detergent, Sulfuric Acid and Hard Make-Up Water#

Cleaning itself can foul a membrane when SLS precipitates below 20 °C (68 °F), when sulfuric acid adds sulfate that precipitates calcium sulfate, or when hard or iron-bearing make-up water exceeds the TSB107 limits of 30 ppm hardness as CaCO3 and 0.05 ppm iron.

Gel, Iron and Silica Foulants That Resist Standard Cleaners#

Three foulants resist the standard caustic and acid pair: the gum-like gel from anionic antiscalant and cationic polymer, iron or aluminum, which needs repeated alkaline EDTA cleaning; iron oxides, which need sodium hydrosulfite; and polymerized silica, for which TSB107 uses caustic alone and some sites use hazardous ammonium bifluoride.

Silica limits and dispersants are covered under silica scale in RO.

Biofilm Regrowth After Incomplete Rinsing#

Biofilm returns after cleaning when nutrients stay behind: Form 45-D01696 warns that unrinsed citric acid may contribute to biofouling, and TSB107 brackets complex-fouling cleans with DBNPA flushes. In biologically active feed, biofilm forms within 3 to 5 days. Online biocide programs and AOC limits belong to membrane biofouling control.

Which Rules Apply to RO Membrane Cleaning Chemicals?#

Two sets of rules apply to RO membrane cleaners, NSF/ANSI/CAN 60 when the permeate becomes drinking water and the discharge rules for spent cleaning solution, plus the hazard rules for handling caustic and acids.

NSF/ANSI/CAN 60 Membrane Cleaner Listings#

A membrane cleaner in a drinking-water plant is certified to NSF/ANSI/CAN 60 under the product function Membrane Cleaner, which held 982 product-function rows for 768 products from 104 companies, 969 rows with maximum use level "NA" and the note "designed to be used off-line and flushed out" (NSF listings, 2026-10-21).

Section 8 covers membrane antiscalants and cleaners; certification is required in 49 US states (NSF survey of ASDWA members). How MULs and the "NA" entry are read is explained under NSF/ANSI/CAN 60. On the same date Descaler held 374 rows. The 3 meanings of MUL "NA" for a cleaner are listed below.

• Off-line: used only while the train is out of service.
• Flushed out: removed before drinking-water service.
• No dose: no numeric concentration remains in finished water.

Spent Cleaning Solution Disposal and Discharge Permits#

Spent RO cleaning solution is treated on site, with oxidants quenched and acids and bases neutralized, and discharged to surface water or a sanitary sewer under State and local rules, where surfactants can complicate approval (EPA 815-R-06-009).

A sewer discharge must not fall below pH 5.0 unless the POTW is designed for it or raise POTW temperature above 40 °C (104 °F) without approval (40 CFR 403.5); local limits come from the POTW's industrial pretreatment program. Direct discharges disclose cleaners as additives under NPDES permits and meet effluent limits and WET tests (40 CFR 122). Among quenching agents, calcium thiosulfate had the lowest half-life in spent cleaning solutions (Ko 2016).

Handling Caustic, Acids and Hydrosulfite#

Caustic soda carries the harmonised CLP Annex VI classification H314 (index 011-002-00-6), hydrochloric acid the harmonised H314 and H335 (index 017-002-01-X) and an OSHA ceiling of 5 ppm (7 mg/m³), and sodium hydrosulfite needs ventilation, so each cleaner is handled to its supplier SDS.

How Does Membrane Cleaning Fit into the Full Reverse Osmosis Chemical Program?#

Membrane cleaning is the off-line half of an RO chemical program: pretreatment chemicals, antiscalants and biocides keep the interval between cleanings long, and cleaners restore the membrane when the trigger is reached.

The full set of reverse osmosis and membrane chemicals is mapped on the membrane hub. Flux, rejection and staging are explained under how reverse osmosis works.

Cleaning Versus Pretreatment, Antiscalants and Biofouling Control#

A plant that cleans more than once a month treats the symptom, and Hydranautics points it to pretreatment instead.

Gel foulants start with the wrong pairing of RO antiscalants and cationic polymers. Coagulation, dechlorination and cartridge filtration are planned under RO pretreatment chemistry.

Preservation After Cleaning, UF Cleaning and Other Cleaning Programs#

After cleaning, a train shut down for more than 48 hours is preserved, and elements kept over 18 months in their original package get an alkaline clean before start-up (Form 45-D01504).

Shutdowns longer than 48 hours move to RO membrane preservation. UF and MBR membranes use chemically enhanced backwash and their own CIP, covered under UF and MBR membrane cleaning chemicals. Other programs use cooling tower cleaning chemicals, boiler chemical cleaning and seawater desalination chemicals.

Can an RO membrane be cleaned?#

Yes: industrial RO and NF elements are cleaned in place with high-pH and low-pH solutions once normalized flow drops about 10 %, and cleaning restores them fully only before performance has fallen 30 to 50 %.

Can hydrogen peroxide be used to sanitize an RO membrane?#

Yes, within limits: DuPont sanitizes its elements with 0.1 wt % hydrogen peroxide in permeate below 25 °C (77 °F), at pH 3 to 4 for 20 minutes, at most once or twice a week, after the alkaline and acid cleans.

Grades and handling are on the hydrogen peroxide page.

Is citric acid enough to clean an RO membrane?#

No, not on its own: citric acid removes carbonate scale and metal oxides, but organic fouling and biofilm need a high-pH cleaner, and Form 45-D01696 calls citric acid less effective than its preferred acids.

How long is an RO membrane rinsed after cleaning?#

An RO membrane is rinsed for 15 to 60 minutes after cleaning, until flush water conductivity is within 10 to 20 % of the feed, and its first permeate goes to drain for at least 30 minutes.

Who Supplies RO Membrane Cleaners and Cleaning Services?#

RO membrane cleaners come as proprietary blends from the 104 companies with NSF/ANSI/CAN 60 Membrane Cleaner listings (NSF listings, 2026-10-21) and as commodity caustic, acids and chelants, while off-site cleaning and CIP programs are bought as a service.

Manufacturer, blender and distributor types are compared under water treatment chemical suppliers. Full RO programs are bought from a water treatment program provider.