Maintaining a Sodium Hypochlorite Generator: Annual Inspection Checklist



Your sodium hypochlorite generator keeps your rig or vessel’s cooling water systems free of biofouling. This system is essential—and expensive. Fortunately, routine maintenance and consistent check-ins on its performance will go a long way towards protecting your hypochlorite generator and its parts as well as your investment.  

However, it’s equally crucial to have an expert inspect your hypochlorite generator from time to time. Your annual inspection will serve as a baseline to help you keep tabs on your generator throughout the year, and also help your team flag issues for immediate maintenance to avoid unpleasant surprises with higher-cost repairs later on. 

Interested in what your inspector will be assessing during your hypochlorite generator’s annual checkup? This checklist will give you an idea of what they will be looking out for.

What an Annual Inspection of a Hypochlorite Generator Includes

Your inspector will review the health of all the components of your hypochlorite generator as well as its performance. They’ll be confirming the following criteria regarding each part of your generator.

Electrochlorination cells 

  • The cleaners used to remove fouling from the cells are of the correct type and concentration. 
  • The electrochlorination cells have been cleaned on a regular schedule and cells have been inspected on a regular basis to ensure the cleaning regimen is working. 
  • All cell bus bars, cables, and associated hardware is tightened properly to prevent overheating.
  • The voltage drop between the cell and transformer/rectifier is appropriate.
  • The solution flow rate through the cells is recorded using a flowmeter or by more mechanically measuring the flow rate.
  • The concentration of sodium hypochlorite in the cell discharge stream is correct.
  • The internal electrode coating condition is good.
  • The voltage of individual cells and their current values are appropriate.
  • The electrolyzer inlet and outlet grounding probes are in good condition.
  • All seals on the cells are in good condition and free from leaks.
  • Flanges on cells are properly torqued.
  • The FRP or PVC components on the cell housings are in good condition, free from degradation and not warped from heat buildup.


  • The shunt voltage and panel DC current are the same.
  • The rectifier is functional in both automatic and manual modes.
  • The rectifier runs appropriately at 25 percent of its full load with a current balanced through SCRs.
  • The rectifier runs appropriately at 50 percent of its full load with a current balanced through SCRs.
  • The rectifier runs appropriately at 100 percent of its full load with a current balanced through SCRs.
  • The oil level is appropriate.
  • All electrical connections are checked and tightened.
  • All terminal connections are tight within the rectifier or control panel.
  • The rectifier DC voltmeter and ammeter are accurate as verified by a multimeter.
  • The rectifier and/or control panel indicates that all lamps are functioning properly.
  • The AC input current to the rectifier is balanced between phases.
  • The oil level switch and oil temperature switch are working well.
  • A sample of the transformer oil is taken for lab review to ensure its free of water and that the insulating properties of the oil are within tolerances.

Degas Tank

  • Any settled hydroxide deposits are removed in the hypochlorite tank.
  • All motor bearings are lubricated on the dilution air blowers.
  • The proper operation of the hydrogen dilution fans is verified including safety shutdown for blower trips.
  • Blower filters if fitted are in good condition.

Dosing Pumps

  • All motor bearings in the hypochlorite dosing pumps are lubricated.
  • All dosing pumps are inspected for noise, leaks, vibration and temperature to see if further evaluation is needed.


  • The instrument transmitter and gauges are working well (including a calibration check).
  • The relief valves are working well.
  • The regulator is working well.
  • The system readings have been logged and a report has been generated.
  • There is no corrosion in the fittings.
  • The instrument air supply is appropriate.
  • The records of alignment on all coupled pumps have been checked or verified.
  • The bearings have all been rotated and checked for free operation or noise.
  • The rotation of pumps and blowers have been verified. 
  • The lubrication points have all been properly serviced.
  • The oil levels have been checked.
  • The oilers have been properly installed on all applicable pumps.
  • The alignment and belt tightness on all belt-driven components have been checked.
  • The solution supply strainer screen has been inspected for cleanliness.
  • The position of equipment valves has been verified
  • The control panel has been energized; it has been confirmed that the correct AC voltage has been supplied.
  • The flow of solution through all piping and cells has been started by working the appropriate pumps or opening the appropriate valves in the relevant supply lines.
  • All systems have been pressurized and all piping checked for leaks.
  • The voltage information has been recorded on the supplemental data sheet.
  • All voltage from across the bus bar/cable has been determined and recorded on the supplemental data sheet.
  • The proper function of each alarm fault has been verified.
  • The complete system operation has been verified in accordance with the “Theory of Operation” in the O&M manual. If there have been any discrepancies, they have been reported to the appropriate H2O personnel.
  • All 4-20 MA signals have been checked for accuracy.
  • The amperage on each motor has been measured and recorded on the supplemental data sheet.
  • The flow switches are functioning well, including set points. 
  • The temperature setting on all temperature switches has been checked and adjusted if required. 
  • Any other observations that could help ascertain the effectiveness of the system have been recorded. 

H2O LLC Provides Trustworthy and Timely Inspection Services

When you need assistance with an annual inspection, you want to work with industry professionals. At H2O, we’re proud to offer parts and services that are helpful, consistent, and accessibly priced. We can help you maintain your sodium hypochlorite generator. The cost of annual inspection is much less than a system failure. Call our friendly team today for more information about the value we can offer you. 

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