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<15% Sodium Hypochlorite (NaOCl)

Recommendations for Storage of <15% Sodium Hypochlorite (NaOCl)

Commonly used for pH adjustment, clean in place (CIP), disinfection of potable water and wastewater and swimming pools.

When storing sodium hypochlorite, or bleach, there are many factors to be considered, such as proper venting, filling slowly and under low pressure delivery, and not overfilling the tank.

Technical Specification for a Sodium Hypochlorite Tank:

Cross-link polyethylene with the tank be rated at a minimum of 1.9 specific gravity.

Fiberglass (fiber reinforced plastic or FRP) tanks by customer preference or due to footprint constraints or larger storage volume requirements.

Secondary Containment

  • Fitting Material:
    PVC, CPVC, or titanium for nozzles
  • Gaskets:
    EPDM or VITON material
  • Bolting Hardware:
  • Special Considerations:
    Avoid direct sunlight; insulation can be used to decrease sodium hypochlorite off gassing and degradation of the NaCl; For indoor, bulk storage applications, vents should be piped externally

All end users should check local regulations to meet secondary containment requirements. Containment must be adequate in capacity and suitable for sodium hypochlorite. Containment should be 10% greater than the largest tank in the containment area. By accepting the delivery of the tank, the customer accepts full responsibility for providing appropriate and adequate containment for the stored material. Eastern Reliability offers a variety of secondary containment options.


All connections below liquid level must prevent chemical from contacting tank wall cross section. Bulkhead style connections can be used on tanks 2,000 gallons and below. Tanks above 2,000 gallons sidewall connections should be titanium construction (flange style fittings are not recommended). Sidewall connections should be installed a minimum of 7″ above the tank floor.

Internal siphon drains can be used if required. Sidewall connections should be kept to a minimum amount and should be placed no closer than 22° apart. Whenever possible, sidewall connections should not be greater than 3″. There are no restrictions on dome fittings.

Flexible Hoses or Expansion Joints (not required for FRP tanks)

Flexible hoses or expansion joints must be used on all lower 1/2 sidewall connections for polyethylene tanks only. A lightweight isolation valve is permitted prior to the flexible joint. Nipple and valve weight must not exceed 8 lbs. All piping must be supported independent of tank. Pipe supports must be installed after the flexible joint to allow the tank to expand and contract under normal service conditions. Polyethylene tanks expand and contract both laterally and vertically, an expansion hose or joint must accommodate for the expansion.

Sodium Hypochlorite

The tank must maintain atmospheric pressure. Vents must be sized for a minimum of two times the largest inlet or outlet port for pneumatically filled tanks. Pump fill tank’s vent should be a minimum of 1.5 to 2 times larger than the largest fill or discharge point. Adequate venting must always be maintained. Under no circumstances should the tank be placed under pressure or vacuum conditions.

Sodium Hypochlorite must not exceed 100°F at delivery or during storage. When practical, tank should be kept from direct sunlight to avoid excessive heat. Excessive heat will degrade the chemical and will accelerate chemical reaction with tank materials.


Deliveries must be regulated. Maximum delivery pressures must not exceed 12 PSI. Ideally, fumes should be vented back into delivery truck during offloading of chemical.

Content Courtesy of Assmann Corporation of America
Assmann Corporation of America