Hydraulic Engineers Evaluate Fatal Injuries Caused by Filter Unit Explosion

Hydraulic Engineering Expert WitnessThis case involves a pool filter that catastrophically malfunctioned, causing fatal injuries to an employee at a public swimming pool in Hawaii. On the date of the incident in question, the employee had been tasked with replacing a filter unit in the pool’s water filtration system. In order to begin the replacement process, the employee depressurized the filtration system and loosened a metal band that secured the filter cartridge while the system was in use. The employee then replaced the cartridge, tightened the band, and re-activated the system. He noticed that the cartridge was leaking under the pressure, and went to apply additional tension to the band. Suddenly, the top of the filter exploded, driving metal fragments into the employee’s face and skull. He was taken to the hospital, where he died shortly after arrival.

Question(s) For Expert Witness

  • 1. Please discuss your background in design pool filter systems.
  • 2. What could have led to the explosion of the two-part pool filter?

Expert Witness Response E-009275

As president of my own consulting firm, I have tested filters like this numerous times. I have extensive experience in designing, engineering, and testing pool filters. As the director of engineering for a major swimming pool manufacturer, I engineered and pressure tested more than 300,000 filters over 10 years. I have seen the accident described in this case hundreds of times; it is referred to as pneumatic separation. I have seen this “explosion” happen hundreds of times, and am familiar with all the causes and preventative measures that could be taken. Normally, filters like this would have warnings on the package or the filter itself against tightening while the filter is on, which may have advised the employee against the dangerous actions he took if it was indeed present.

Expert Witness Response E-009900

I have a great deal of experience with pool filters, and I have examined and tested various types of filters on multiple occasions. I believe that the tightening bands were not designed properly. I have trained thousands of people on pool operation and this includes the proper stabilizing and changing of filters. The big problem with this specific pool filter is that there is no automatic air release valve. There are safer alternatives that employ automatic release that should be used in more pools. The warnings and pictures some manufacturers use to specify safety standards are often inadequate. People routinely ignore the warnings, and those who do read the label may still be confused as the pictures imply that a leak will be harmless, whereas a leak could result in a blown cap that could launch 200 feet in the air. Similar filters have been taken off the market because they are unsafe as well.


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