Sodium hypochlorite (NaOCl; CAS 7681-52-9) is the liquid chlorine disinfectant and oxidant that water treatment plants dose from bulk solutions of 10 to 15 % available chlorine. Its strength is stated in trade % (g/L of available chlorine divided by 10), so a 12.5 trade % product holds 125 g/L, which is 11.23 wt % NaOCl.
The most common NSF/ANSI/CAN 60 maximum use level is 84 mg/L as product, about 9.0 mg/L as Cl2 (NSF listings, 2026-10-21), and a 15 % solution loses half its strength in about 100 days. Sodium hypochlorite is one of the disinfectants in this reference of water treatment chemicals, each documented with the same identity, dose and compliance fields.
The identity card below summarizes the attributes that define sodium hypochlorite.
| Attribute | Value |
|---|---|
| Name | Sodium hypochlorite |
| Abbreviation and formula | NaOCl (NaClO), 74.44 g/mol |
| Synonyms | hypochlorite, hypo, bleach, liquid bleach, soda bleach, Javel water, sodium hypochlorite solution |
| CAS number | 7681-52-9 |
| EC number | 231-668-3 |
| Class | Inorganic hypochlorite salt (chlor-alkali derivative) |
| Function | Disinfectant, oxidizing biocide, oxidant |
| Delivered strength | 10 to 15 % available chlorine; 12.5 and 15.5 wt % NaOCl most common |
| NSF/ANSI/CAN 60 | Product-specific MUL; 84 mg/L as product most common (NSF listings, 2026-10-21) |
| AWWA and EN standards | ANSI/AWWA B300-24; EN 901:2024 |
| GHS | Harmonised CLP Annex VI (index 017-011-00-1): EUH031, H314, H318, H400, H410; Danger |
| Transport and customs | UN1791 Hypochlorite solutions, class 8, PG II or III; HS 2828.90 (US HTS 2828.90.00.00) |
Every value on this page is checked against primary sources (NSF listings, AWWA, CEN, EPA, eCFR, EUR-Lex, WHO); see our methodology and fact-checking process.
What Is Sodium Hypochlorite?#
Sodium hypochlorite is an inorganic hypochlorite salt from the chlor-alkali chain, supplied as a solution stabilized with excess sodium hydroxide (at least 0.1 to 0.2 wt % as NaOH, Olin's sodium hypochlorite handbook).
Its other names are hypo, liquid bleach and Javel water. "Liquid chlorine" is trade usage only: ANSI/AWWA B301-24 "Liquid Chlorine" covers liquefied chlorine gas, while hypochlorites fall under ANSI/AWWA B300-24.
What strengths is sodium hypochlorite sold in? Trade %, wt % and g/L#
Sodium hypochlorite is sold at 10 to 15 % available chlorine, most often as 12.5 or 15.5 wt % NaOCl, and trade % equals g/L of available chlorine divided by 10. A 12.5 trade % solution holds 125 g/L (11.23 wt % NaOCl), while a 12.5 wt % solution holds 142 g/L (14.2 trade %). Available chlorine by weight equals wt % NaOCl x 0.952 (70.90 / 74.44).
The table below converts five strengths between units (theoretical values from the same handbook).
| wt % NaOCl | g/L available chlorine | Trade % | lb Cl2 per gal | Density (g/mL) |
|---|---|---|---|---|
| 10.84 | 120 | 12.0 | 1.00 | 1.163 |
| 11.23 | 125 | 12.5 | 1.04 | 1.169 |
| 12.50 | 142 | 14.2 | 1.18 | 1.189 |
| 13.13 | 150 | 15.0 | 1.25 | 1.199 |
| 15.50 | 183 | 18.3 | 1.52 | 1.238 |
What is the density of sodium hypochlorite solution?#
Sodium hypochlorite solution has a density of 1.163 to 1.238 g/mL across 10.84 to 15.50 wt % NaOCl, and 1.169 g/mL at 12.5 trade % (theoretical). Density does not track strength as a solution ages, so the same handbook advises buying on a g/L assay by titration, not on specific gravity.
On-site generated sodium hypochlorite (0.8 %)#
On-site generators make a dilute sodium hypochlorite of 0.5 to 1.0 % (m/V) by brine electrolysis, with a product tank of about 3 days' supply (UK Drinking Water Inspectorate). One maker's system, the De Nora ClorTec, makes 0.8 ± 0.05 % from 2.2 % brine with 3.0 kg salt and 4.4 kWh per kg of chlorine (3.0 lb salt, 2.0 kWh per lb) and vents hydrogen below 25 % of its lower explosive limit.
The EU treats electrolytic active chlorine as a separate active substance, approved for PT2 to PT5 by Implementing Regulation (EU) 2021/345 (2022-07-01 to 2032-06-30). Bromide in the salt yields bromate (WHO). Cell types are covered under chlorinators and hypochlorite generation systems.
How Does Sodium Hypochlorite Disinfect Water?#
Sodium hypochlorite disinfects water by hydrolyzing to hypochlorous acid (NaOCl + H2O → HOCl + NaOH), which oxidizes the cell components of microorganisms. HOCl is about 100 times more effective than the hypochlorite ion (OCl-), according to the DuPont FilmTec chlorination and dechlorination manual.
The same free chlorine oxidizes iron, manganese, taste and odor compounds. Speciation is part of water chlorination chemistry.
Why does pH decide how well hypochlorite works?#
pH decides performance because hypochlorous acid (pKa 7.54 at 25 °C (77 °F), Morris 1966) dissociates into the weaker OCl- ion as pH rises: HOCl is about 90 % of free chlorine at pH 6.5, 50 % at pH 7.5 and about 10 % at pH 8.5 (calculated). WHO's 2017 technical note therefore pairs its residual target with a pH below 8.0.
Where Is Sodium Hypochlorite Used? Drinking Water, Wastewater, Cooling and Membranes#
Sodium hypochlorite is used in 4 water systems: drinking water, wastewater, cooling towers and membrane plants (RO pretreatment and UF cleaning). The table below compares its uses by dose basis, feed point, control and target.
| System | Dose (basis) | Feed point | Control | Target or note | Source |
|---|---|---|---|---|---|
| Drinking water | To ≥ 0.5 mg/L free chlorine after ≥ 30 min at pH < 8.0 | Pre-oxidation, clearwell, entry point, booster stations | Free chlorine (SM 4500-Cl D, F, G) | Entry point ≥ 0.2 mg/L; MRDL 4.0 mg/L as Cl2; pre-oxidation for iron and manganese removal, taste and odor, algae | WHO 2017; 40 CFR 141 |
| Municipal wastewater | 5 to 20 mg/L as Cl2 | Baffled contact basin, initial mixing < 1 s | Total residual chlorine, ORP | Permit TRC after dechlorination; odor control in hydrogen sulfide and odor control programs | EPA 832-F-99-062 |
| Industrial wastewater | Stoichiometric, by cyanide load | Alkaline reactor | pH, ORP | Alkaline chlorination for cyanide destruction | Site-specific |
| Cooling towers | 0.5 to 1.0 ppm free as Cl2, continuous; remediation ≥ 20 ppm, then 10 ppm for ≥ 24 h | Basin or return line | Free chlorine, ORP | Steam electric cooling tower blowdown: FAC 0.5 mg/L max, 0.2 mg/L average | CTI; CDC; 40 CFR 423.13 |
| RO pretreatment | 0.5 to 1.0 mg/L free chlorine, 20 to 30 min | Intake; SMBS upstream of cartridge filters | ORP, 175 to 200 mV trip | < 0.1 mg/L at polyamide membranes; membrane biofouling control | DuPont FilmTec manual |
| UF cleaning | CEB 0.1 % NaOCl + 0.05 % NaOH; CIP 0.2 % NaOCl + 0.1 % NaOH | Backwash water | Free chlorine | PVDF modules max 2,000 mg/L (IntegraFlux data sheet); ultrafiltration membrane cleaning chemicals | Dow UF manual (2011) |
Drinking water: primary and residual disinfection#
Drinking-water plants dose sodium hypochlorite to a free chlorine residual, not a fixed mg/L: at least 0.5 mg/L free chlorine after 30 minutes of contact at pH below 8, and at least 0.2 mg/L at delivery (WHO technical note, 2017). Primary and secondary disinfectants are compared under drinking water disinfection.
Chlorine oxidizes manganese effectively only above pH 9; at pH 7 and 25 °C (77 °F) it needs at least 3 hours (Health Canada, citing Knocke et al. 1990).
Free chlorine earns 3-log Giardia credit at a CT of 112 mg-min/L (1.0 mg/L, pH 7.0, 10 °C (50 °F)), against 1,850 mg-min/L for chloramines (EPA profiling guidance), but it is not effective against Cryptosporidium. Log credits sit with CT values for disinfection.
Wastewater: effluent disinfection and odor control#
Municipal wastewater plants dose 5 to 20 mg/L (ppm) as Cl2 into a baffled contact basin with initial mixing in under 1 second (EPA fact sheet 832-F-99-062). Dechlorination adds about 30 to 50 % to the cost of chlorination, a design point covered under wastewater disinfection and dechlorination.
One plant in the same fact sheet held total residual chlorine at 0.1 to 0.2 mg/L by ORP control, and the East Bay Municipal Utility District (EBMUD) uses hypochlorite for odor control in initial treatment.
Bisulfite and thiosulfate ratios are compared under dechlorination chemicals.
Cooling towers: microbial and Legionella control#
Cooling towers run sodium hypochlorite to a continuous free residual of 0.5 to 1.0 ppm as Cl2 in the hot return water (Cooling Technology Institute), and OSHA guidance cites free chlorine above 0.5 ppm with pH below 8.0. Oxidizing and non-oxidizing programs are compared under cooling tower biocides.
For remediation, CDC sets at least 20 ppm free chlorine, then 10 ppm for at least 24 hours. At steam electric plants, 40 CFR 423.13 limits blowdown discharge of free available chlorine to 2 hours per day per unit. Water management plans are covered under Legionella control in cooling towers.
Membrane systems: RO pretreatment and UF cleaning#
Sodium hypochlorite protects RO pretreatment from biofouling but is removed before polyamide membranes, which tolerate less than 0.1 mg/L free chlorine and degrade after about 200 to 1,000 ppm-hours (DuPont FilmTec chlorination and dechlorination manual). Sodium metabisulfite removes 0.5 to 1.0 mg/L of pretreatment chlorine at 1.34 mg per mg Cl2 in theory and about 3.0 mg in practice, and an ORP of 175 to 200 mV trips the high-pressure pump. ORP placement is covered under RO pretreatment chemistry.
Ultrafiltration membranes are cleaned with hypochlorite: the Dow UF product manual (2011) gives 0.1 % NaOCl with 0.05 % NaOH for chemically enhanced backwash and 0.2 % NaOCl with 0.1 % NaOH for clean-in-place.
How Is the Sodium Hypochlorite Dose Calculated and Fed?#
The daily sodium hypochlorite feed is lb/day = mg/L x MGD x 8.34 / purity (Florida DEP), where the dose equals chlorine demand plus target residual. At 2.0 mg/L as Cl2 and 10 MGD (37,854 m³/d), a plant feeds 75.7 kg/d (166.8 lb/day) of chlorine.
The worked example below labels every input; all results are calculated.
| Worked example | Metric | US customary |
|---|---|---|
| Input: flow | 37,854 m³/d | 10 MGD |
| Input: dose, as Cl2 | 2.0 mg/L | 2.0 ppm |
| Input: product strength | 125 g/L available chlorine (12.5 trade %) | 1.04 lb Cl2 per gal |
| Input: product density | 1.169 g/mL | 1.169 g/mL |
| Result: available chlorine | 75.7 kg/d | 166.8 lb/day |
| Result: as NaOCl (÷ 0.952) | 79.5 kg/d | 175 lb/day |
| Result: product volume | about 606 L/d | about 160 gal/d |
| Result: product mass | about 708 kg/d | about 1,561 lb/day |
| Result: dose as product | about 18.7 mg/L | about 18.7 ppm |
How do you convert a dose as Cl2 into a volume of hypochlorite?#
Divide the chlorine mass by the product's g/L of available chlorine: 75.7 kg/d at 125 g/L is about 606 L/d (160 gal/d) of 12.5 trade % product (worked example, calculated). A wt % value needs the density first: 11.23 wt % x 1.169 g/mL is about 131 g/L NaOCl, or 125 g/L as Cl2.
Florida DEP's strength formula assumes 8.34 lb/gal, the weight of water, while real solutions run 1.16 to 1.24 g/mL. The dosage and feed rate calculator converts other flows to kg/d, lb/day and L/h.
Which pumps, piping and materials does hypochlorite feed use?#
Hypochlorite feed systems use fluoropolymer and PVC wetted parts, with titanium as the only suitable metal (Olin handbook). The 4 rules below come from that handbook and the Powell hypochlorite handbook.
- Wetted parts: PTFE, ETFE, ECTFE, PVDF and PVC.
- Piping: PVC or CPVC Schedule 80, socket welded, no threads; failures above 50 to 60 psi (3.4 to 4.1 bar); 1.5 to 2.1 m/s (5 to 7 ft/s).
- Pumps: Viton outlasts EPDM; titanium pump seals last 3 to 5 years, lined magnetic-drive pumps 3 to 7 years.
- Valves: vented-ball valves, since decomposition oxygen over-pressures liquid trapped in closed PVC ball valves.
Oxygen bubbles also cause vapor lock at low flow, so suction piping slopes away from the pump. Pump types are compared under chemical dosing pumps.
How Is Hypochlorite Dosing Controlled? Residual Tests, ORP and pH#
Hypochlorite dosing is controlled by the free chlorine residual, with ORP and pH as supporting signals. Because dose equals demand plus residual, a residual that falls at a steady feed rate signals rising demand, as shown under breakpoint chlorination and chlorine demand.
The 4 measurements below control a hypochlorite feed.
- Free chlorine: SM 4500-Cl D, F, G or H, or ASTM D1253; DPD kits only where the State approves them (40 CFR 141.74).
- Total chlorine: SM 4500-Cl E and I, for chloraminated systems and effluents.
- ORP: the signal for wastewater residuals and RO trips, explained under ORP in water treatment.
- pH: held below 8.0 where free chlorine must disinfect.
Analyzers are checked against a grab sample every 5 days. The entry-point residual may not fall below 0.2 mg/L for more than 4 hours, and distribution samples may lack a residual in no more than 5 % per month for 2 consecutive months (40 CFR 141.72).
Free, combined and total forms are defined under chlorine residual. NPDES samples for total residual chlorine are analyzed within 15 minutes (40 CFR 136.3).
What Must Never Be Mixed with Sodium Hypochlorite?#
Sodium hypochlorite must never be mixed with acids, acidic coagulants, ammonium salts, urea and amines, or reducing agents. The 5 incompatible groups are listed below.
- Acids (hydrochloric, sulfuric, acetic): release chlorine; neutralize hypochlorite before lowering pH (Olin handbook).
- Acidic coagulants (ferric chloride, alum): release chlorine (Minnesota Pollution Control Agency).
- Ammonium salts with acid: formed nitrogen trichloride that decomposed explosively (HSDB 748).
- Urea and primary amines: form nitrogen trichloride and explosive chloroamines (HSDB 748).
- Reducing agents, such as sodium bisulfite.
An INERIS review of 72 unloading accidents (1953 to 2019) found hypochlorite with hydrochloric acid in 24 % and with ferric chloride in 13 % of cases, and a toxic dispersion in 90 %. At MGPI Processing in Atchison, Kansas, on 2016-10-21, sulfuric acid entered an unlabeled hypochlorite fill line (US Chemical Safety Board). Unloading controls are covered under water treatment chemical compatibility.
Which Standards Cover Sodium Hypochlorite? NSF/ANSI/CAN 60, AWWA B300 and EN 901#
Three documents cover sodium hypochlorite for drinking water: NSF/ANSI/CAN 60 for health effects, ANSI/AWWA B300-24 for product quality in North America and EN 901:2024 in Europe. The table below adds the salt standards for electrochlorination.
| Document | Scope | Edition or status | Key requirement |
|---|---|---|---|
| NSF/ANSI/CAN 60 | Drinking water treatment chemicals, health effects | Listings read 2026-10-21 | Product-specific MUL as product, 84 mg/L most common; minimum MUL 2 mg/L as Cl2; bromate SPAC 0.0033 mg/L |
| ANSI/AWWA B300-24 | Hypochlorites (chlorinated lime, calcium and sodium hypochlorite) for water, wastewater and reclaimed water | Current; supersedes B300-18 | FIFRA registration required for disinfection use; see AWWA B-series standards |
| EN 901:2024 | Sodium hypochlorite for water intended for human consumption | Published 2024-12-17; replaces EN 901:2013 | Scope excludes in-situ generated hypochlorite, but its impurity and chemical-parameter limits apply to it; see EN standards for drinking water treatment chemicals |
| EN 14805:2022 and EN 16370:2022 | Salt for non-membrane and membrane-cell electrochlorination | CEN/TC 164 catalogue, 2026-10-20 | Feedstock salt quality for on-site generation |
What is the NSF/ANSI/CAN 60 maximum use level for sodium hypochlorite?#
No single NSF/ANSI/CAN 60 limit exists: maximum use levels are product-specific, and 84 mg/L as product is the most common (273 product-function rows), followed by 40 and 105 mg/L (NSF listings, 2026-10-21). Most listings fall between about 40 and 210 mg/L, with outliers from 15 to 500 mg/L. For a 12.5 trade % product, 84 mg/L as product is about 9.0 mg/L as Cl2 (84 x 125 / 1,169, calculated).
The standard sets a minimum hypochlorite MUL of 2 mg/L as Cl2, a bromate SPAC of 0.0033 mg/L and manufacturing dates on shipping documents (2020 text, 6.3.3). Listing notes are covered under NSF/ANSI/CAN 60 certification.
The listings cover 178 companies, 768 products (company plus trade designation), 1,551 product-function rows and 411 facility entries (NSF listings, 2026-10-21); 49 US states require NSF/ANSI/CAN 60 through legislation, regulations or policies (NSF survey of ASDWA members).
Why do chlorate and bromate matter in hypochlorite specifications?#
Chlorate and bromate matter because stored hypochlorite decomposes to chlorate (3 NaOCl → NaClO3 + 2 NaCl), and hypochlorite made from bromide-containing salt carries bromate. Nickel, cobalt, copper and light catalyze a second path to oxygen (OxyChem sodium hypochlorite handbook).
Chlorate above 1 mg/L is unusual unless hypochlorite was stored badly (WHO), and at the NSF maximum use level hypochlorite adds a mean of 2.5 µg/L bromate (range 0.10 to 26 µg/L, Health Canada). The EU limits chlorate to 0.25 mg/L, or 0.70 mg/L with chlorate-generating disinfection, from 2026-01-12 (Directive (EU) 2020/2184); the US has no chlorate MCL. The 4 WHO controls are listed below.
- Buy fresh product.
- Store it cool and dark.
- Use it within about a month.
- Never add new solution to old.
Chlorate sits with THMs and HAAs among the disinfection byproducts.
What Is the Regulatory Status of Sodium Hypochlorite?#
Sodium hypochlorite needs FIFRA registration for disinfection use, is not listed in 21 CFR 173.310, and is limited in US drinking water by the MRDL of 4.0 mg/L as Cl2 (status 2026-10-22). Active chlorine released from sodium hypochlorite is approved for PT1 to PT5 (Implementing Regulation (EU) 2017/1273, 2019-01-01 to 2028-12-31); its PT11 and PT12 uses are still under evaluation in the EU review programme, with no decision as of 2026-10-22. Its place among utility chemicals is shown under drinking water treatment chemicals.
The table below lists the limits and listings that apply to sodium hypochlorite (status 2026-10-22).
| Instrument | Value | Type | Reference |
|---|---|---|---|
| US MRDL | 4.0 mg/L as Cl2, running annual average | Maximum residual disinfectant level | 40 CFR 141.65 under the Safe Drinking Water Act |
| US DBP MCLs | TTHM 0.080 mg/L and HAA5 0.060 mg/L (LRAA); bromate 0.010 mg/L | MCL | 40 CFR 141.64 |
| US chlorate | No MCL; MDBP revision not yet proposed | n/a | EPA six-year review |
| US perchlorate | MCLG 0.02 mg/L; MCL options 0.02, 0.04 or 0.08 mg/L | Proposal (91 FR 398, 2026-01-06; comments closed 2026-03-09) | Not final |
| European Union | Chlorate 0.25 mg/L (0.70 mg/L with chlorate-generating disinfection); bromate 10 µg/L; THMs 100 µg/L; HAA5 60 µg/L; from 2026-01-12 | Parametric values | Annex I Part B of the EU Drinking Water Directive 2020/2184 |
| Health Canada | Chlorine: no MAC required (2009); chlorate MAC 1 mg/L (2008) | Guideline | Guidelines for Canadian Drinking Water Quality |
| FIFRA | Registered pesticide product required for disinfection use | Registration | ANSI/AWWA B300-24 scope; FIFRA registration |
| EU BPR | PT1 to PT5 approved, 2019-01-01 to 2028-12-31; PT11 and PT12 under evaluation, no decision as of 2026-10-22 | Biocidal active substance | Implementing Regulation (EU) 2017/1273; EU Biocidal Products Regulation |
| Discharge | Blowdown FAC 0.5 mg/L max, 0.2 mg/L average; once-through at plants ≥ 25 MW TRC 0.20 mg/L; aquatic criteria (1986) freshwater CMC 19 µg/L, CCC 11 µg/L, saltwater CMC 13 µg/L, CCC 7.5 µg/L | ELG; water quality criteria | 40 CFR 423.13; effluent limitations guidelines |
| 21 CFR 173.310 | Not listed in 21 CFR 173.310 | n/a | eCFR |
| EPA RMP / OSHA PSM | Not listed | n/a | 40 CFR 68.130; 29 CFR 1910.119 App. A; EPA RMP and OSHA PSM |
Is 4.0 mg/L an MCL for chlorine?#
No: 4.0 mg/L as Cl2 is the maximum residual disinfectant level (MRDL) for chlorine under 40 CFR 141.65, met as a running annual average, not a maximum contaminant level. The by-product MCLs are separate: TTHM 0.080 mg/L, HAA5 0.060 mg/L and bromate 0.010 mg/L (40 CFR 141.64). Compliance is explained under disinfectants and disinfection byproducts rules.
How Should Sodium Hypochlorite Be Stored and Handled Safely?#
Sodium hypochlorite is stored cool, closed and out of sunlight in rubber-lined steel or fiberglass tanks, with no more than one month's supply delivered at a time (EPA 832-F-99-062; UK DWI). Olin's handbook sizes tanks at 1.5 times the delivery or more, and two tanks used alternately keep new product out of old.
The Recommended Standards for Water Works (2022 edition, 5.5.10) require separate vents, incompatible chemicals stored apart and containment for the largest tank. No OSHA PEL, NIOSH REL or IDLH exists for sodium hypochlorite. Containment is covered under chemical storage tanks.
The table below summarizes storage and handling data.
| Item | Value | Source |
|---|---|---|
| Tank materials | Chlorobutyl rubber-lined steel; FRP (no cobalt naphthenate cure, UV inhibitor); HDPE or XLPE to ASTM D1998 (embrittles with time) | Olin handbook |
| XLPE tank system | Antioxidant inner layer, 1.9 SG rating for 2 to 15 %; keep below 38 °C (100 °F); no stainless steel or C-276 | Poly Processing |
| Metals | Titanium and tantalum only | Olin handbook |
| Tank size | ≥ 1.5 x bulk delivery; two tanks used alternately | Olin; Powell |
| Delivered supply | ≤ one month's supply | UK DWI |
| Storage temperature | Near 15 °C (60 °F) | Powell |
| Freezing point | 12 wt % -19.4 °C (-3 °F); 15.6 wt % -29.7 °C (-21.5 °F) | OxyChem handbook |
| Exposure limits | No OSHA PEL, NIOSH REL or IDLH | 29 CFR 1910.1000; NIOSH Pocket Guide |
| Process safety | Not listed under EPA RMP or OSHA PSM | 40 CFR 68.130; 29 CFR 1910.119 |
How fast does sodium hypochlorite lose strength?#
Sodium hypochlorite loses half its strength in about 100 days at 15 %, 220 days at 10 % and 790 days at 5 % (AWWA M20, cited by WHO in 2017). Decomposition is second order, so a 200 g/L solution decomposes about 4 times faster than a 100 g/L solution, and storage near 15 °C (60 °F) slows it (Powell hypochlorite handbook). A minimum excess caustic of 0.3 g/L (about pH 11.86) stabilizes the solution. The EPA supply chain profile gives a shelf life of about 1 month and a truck radius of 250 to 300 miles (400 to 480 km).
What does a sodium hypochlorite safety data sheet (SDS) cover?#
A sodium hypochlorite safety data sheet states the harmonised CLP Annex VI classification (index 017-011-00-1: EUH031, H314, H318, H400, H410; Danger) and the transport entry UN1791, class 8. Notified ECHA C&L entries add H290 (32.2 % of 3,101 notifications), which is not harmonised; M-factors appear on the supplier SDS.
The table below lists the codes a sodium hypochlorite SDS carries.
| Code | Meaning | Basis |
|---|---|---|
| EUH031 | Contact with acids liberates toxic gas | Harmonised (CLP Annex VI) |
| H314 | Causes severe skin burns and eye damage | Harmonised (CLP Annex VI) |
| H318 | Causes serious eye damage | Harmonised (CLP Annex VI) |
| H400 | Very toxic to aquatic life | Harmonised (CLP Annex VI) |
| H410 | Very toxic to aquatic life with long lasting effects | Harmonised (CLP Annex VI) |
| H290 | May be corrosive to metals | Notified (ECHA C&L), 32.2 % of notifications |
| GHS05, GHS09 | Corrosion and environment pictograms | Harmonised label |
| UN1791 | Hypochlorite solutions, class 8, PG II or III by concentration | 49 CFR 172.101 |
| HS 2828.90 | Hypochlorites, other (US HTS 2828.90.00.00) | USITC, checked 2026-10-20 |
Check the 4 items below against the delivered grade.
- Confirm the name, CAS 7681-52-9 and g/L strength against the certificate of analysis.
- Compare the hazard section with EUH031, H314, H318, H400 and H410.
- Verify the packing group for the delivered concentration.
- Read the incompatibility section at the unloading point.
What Are the Alternatives to Sodium Hypochlorite?#
Five alternatives replace or complement sodium hypochlorite: chlorine gas, calcium hypochlorite, chlorine dioxide, monochloramine and ozone. Strength loss, chlorate formation and a 1-month shelf life are hypochlorite's disadvantages.
The table below compares the alternatives with sodium hypochlorite.
| Disinfectant | Form | US residual limit | NSF/ANSI/CAN 60 | AWWA | RMP / PSM |
|---|---|---|---|---|---|
| Sodium hypochlorite | Liquid, 10 to 15 % available chlorine | MRDL 4.0 mg/L as Cl2 | 84 mg/L as product most common | B300-24 | Not listed |
| Chlorine gas | Liquefied gas | MRDL 4.0 mg/L as Cl2 | 30 mg/L most common | B301-24 | RMP 2,500 lb (1,134 kg); PSM 1,500 lb (680 kg) |
| Calcium hypochlorite | Solid, 65 to 70 % granules and tablets | MRDL 4.0 mg/L as Cl2 | 15 mg/L most common | B300-24 | Not listed |
| Chlorine dioxide | Generated on site | MRDL 0.8 mg/L as ClO2; chlorite MCL 1.0 mg/L | No listing under its own name | n/a | RMP and PSM 1,000 lb |
| Monochloramine | Formed on site from chlorine and ammonia | MRDL 4.0 mg/L as Cl2 | No listing under its own name | n/a | Anhydrous ammonia 10,000 lb under both |
| Ozone | Generated on site | Bromate MCL 0.010 mg/L | No listing under its own name | n/a | PSM 100 lb; not RMP |
Sodium hypochlorite vs chlorine gas#
Sodium hypochlorite and chlorine gas deliver the same free chlorine, but chlorine gas is listed under EPA RMP at 2,500 lb (1,134 kg) and OSHA PSM at 1,500 lb (680 kg), while hypochlorite is listed under neither. Chlorine gas follows ANSI/AWWA B301-24 and carries an OSHA ceiling PEL of 1 ppm; hypochlorite has no PEL. Cylinders and thresholds are covered under chlorine gas.
Sodium hypochlorite vs calcium hypochlorite#
Calcium hypochlorite is the solid alternative: 65 to 70 % granules and tablets (CAS 7778-54-3, UN2880), classified in CLP Annex VI (index 017-012-00-7) as H272, H302, H314 and H400, so it is also an oxidizer. Its most common NSF/ANSI/CAN 60 MUL is 15 mg/L as product (NSF listings, 2026-10-21). Searches for sodium hypochlorite powder usually mean this solid. Tablet grades are covered under calcium hypochlorite.
Sodium Hypochlorite Grades, Suppliers and Sourcing#
Sodium hypochlorite is supplied as bulk solutions of 10 to 15 % available chlorine and is one of the 36 chemicals in EPA's water treatment supply chain profiles. Winter Storm Uri took out about 28 % of US chlor-alkali capacity in February 2021 (EPA chlorine profile). Regional producers are listed under water treatment chemical suppliers.
The table below lists companies named in the EPA sodium hypochlorite profile. Listed alphabetically; no company is a partner of this site and none pays for inclusion.
| Company | Role |
|---|---|
| HASA | Manufacturer |
| Odyssey Manufacturing | Manufacturer |
| Olin | Manufacturer |
| OxyChem (Occidental) | Manufacturer |
| Univar | Distributor |
| Westlake | Manufacturer |
How is sodium hypochlorite priced and quoted?#
Compare sodium hypochlorite offers per kg (lb) of available chlorine, not per gallon, because strength differs by grade and falls with age. Quote factors are g/L strength, manufacturing date, volume, container, freight distance, contract term and NSF/ANSI/CAN 60 MUL.
Public procurement records show what buyers paid at a given date and place; they include delivery and local terms and are not a current price. The Bay Area Chemical Consortium in California received 2 bids of USD 3.45 to 3.61 per gallon as product for 12.5 % bulk solution, delivered by region (bid opening 2026-02-19, BACC Project 13-2026). The table below lists five further bid tabulations, each from one document.
| Date | Region | Product | Range | Basis | Source |
|---|---|---|---|---|---|
| 2025-11-13 (publication, term 2026) | SWOP4G members, Dayton region, Ohio, US | Liquid, bulk delivery, 4 bids | USD 1.60 to 2.85 | Per gallon as product, delivered by site | SWOP4G 2026 Water Treatment Chemicals Bid Tabulation |
| 2025-06-23 (bid opening, term FY26) | Emporia, Virginia, US | Bulk, 13,000 gal annual, 4 bids | USD 1.85 to 3.698 | Per gallon | City of Emporia bulk chemical bid tabulation |
| 2025-03-12 (bid opening) | Township of Livingston, New Jersey, US | 15 %, bulk, 4 bids | USD 3.390 to 4.15 | Per gallon | Township of Livingston Bid 6-2025 tabulation |
| 2025-02-05 (bid opening, term 2025) | Hanover Borough and Penn Township, Pennsylvania, US | 12 % solution, bulk, 2 bids | USD 0.164 to 0.1975 | Per pound | Joint municipal bid results opened 2025-02-05 |
| 2024-10-24 (publication, term 2025) | Lima, Ohio, US | Bulk, freight included, 4 bids | USD 1.81 to 2.40 | Per gallon, delivered | City of Lima 2025 chemical bid tabulation |
Send one specification on one g/L basis to request quotes for water treatment chemicals.
Where Does Sodium Hypochlorite Sit Among Oxidants for Water Treatment?#
Sodium hypochlorite is the liquid member of the chlorine-based oxidants, beside chlorine gas, calcium hypochlorite and chlorine dioxide. All oxidants are compared under oxidants and oxidizing biocides. In cooling and membrane systems, hypochlorite is the oxidizing half of programs whose non-oxidizing options are covered under biocides for water treatment.
Sodium hypochlorite FAQs#
Is sodium hypochlorite the same as bleach?#
Yes: bleach is a common name for sodium hypochlorite solution; water-treatment grades carry 10 to 15 % available chlorine and are bought against ANSI/AWWA B300-24 and NSF/ANSI/CAN 60.
Is sodium hypochlorite the same as sodium chlorite?#
No: sodium chlorite (NaClO2) is a different salt, the chlorine dioxide precursor, with its own standards, ANSI/AWWA B303-24 and EN 938:2016.
Its uses are covered under sodium chlorite.
Does sodium hypochlorite raise pH?#
Yes, slightly: hydrolysis releases sodium hydroxide (NaOCl + H2O → HOCl + NaOH), which raises pH and alkalinity.
Final pH adjustment with acid or sodium hydroxide (caustic soda) follows the treatment target.
Does sodium hypochlorite freeze?#
Yes: a 12 wt % solution freezes at -19.4 °C (-3 °F) and a 15.6 wt % solution at -29.7 °C (-21.5 °F), according to the OxyChem sodium hypochlorite handbook. A 6 wt % solution freezes at -7.5 °C (18.5 °F).