Explosion des Poolfilters
As we bid farewell to this winter beset by atmospheric torrents of precipitation, many are ready to celebrate the spring and summer pool parties. But there's a hazard in many homeowners' backyards that you may not be aware of: pool filter explosion.
Most filters consist of a tank, a lid, and a bracket that holds the system together (Figure 1). The filter works under high pressure created by a mixture of water and air. The cap can pop off the tank with tremendous force if there is too much pressure and the clamp fails.
Failure can be catastrophic due to the extremely high pressure that can build up in the filter and cause an explosion. We have seen cases of the filter cover damaging awnings and roofs, catching in trees and damaging pool roofs. When the pool filter cover hits a person, we've seen severe traumatic brain injury, death, traumatic eye loss, and multiple fractured facial bones.
Pool filters pose an explosion hazard
A pool filter cleans dirt from the water. Typically, a filter consists of a two-piece canister, a base and a top, molded from durable plastic. The bottom of the tank contains a filter cartridge that cleans the water as it flows through the system. A pump moves water from the pool to the filter and back to the pool (Figure 2).
A filter tank can trap or trap air. The output from the pump compresses the trapped air and pressurizes the filter. This creates the risk of explosion or "sudden separation" of the filter parts. Filter manufacturers have known about the risk of explosion since at least the early 1970's. In 1974, the United States Consumer Product Safety Commission ("CPSC") published an article reporting "Explosion Problems in Filter Tanks" (Figure 3).
Consumer Product Safety Division data shows dozens of explosions like the one that disfigured our customers. Manufacturers know this problem:
1982: Filter cap “exploded” and flew 30 feet up;
1983: the filter had a "pressure-induced" explosion;
1983: a coverage of the "pink" filter 3 meters;
1985: "exploded" filter on the man's face;
1985: Filter cover exploded in pool technician's face;
1985: The filter cap exploded in the man's face;
1986: Filter cap exploded in victim's face;
1986: "The operator reassembles the filter...observes a rise in pressure, stretches his hand over the filter...and the filter explodes...";
1989: Filter cap ruptured and victim's skull fractured;
1990: Filter exploded on a man's head; semi-comatose man;
1991: Filter cap exploded on woman's head, killing her;
1993: Filter cap exploded on man's head;
1994: Filter explodes, causing blindness and brain damage;
1998: The filter cap burst, flying two meters high and hitting the man in the face.
1998: The lid exploded in the man's face, knocking him unconscious;
2005:Filter exploded in father's face causing brain damage;
2006:the filter cap exploded in the owner's face, killing him;
2006: Filter cap exploded in 37-year-old mother who lost an eye;
2006:Boy saw a filter explode in his father's face, who died.
Cal-OSHA has studied the prevalence of pool filter explosions. This investigation found that the filter explosion harms consumers and workers.
Cheap solutions are ignored
A manufacturer can easily equip a filter system with different types of fasteners to connect the top and bottom together. Some fasteners, like nuts and eyelets, hold covers in place better than others. They ensure that the lid does not break under pressure.
An inferior fastener such as Items such as a clamp (Figure 1) can bend, break, or deteriorate and result in the filter cover being pushed out with excessive force. For example, CPSC recalled 8,500 pool filters in 2004 because the filter holder "may become detached from the bottom tank housing, causing the top filter housing to detach and injuring nearby customers."
Pool filter manufacturers knew, or should have known, about explosion hazards before designing almost all of the pool filters in use today. In 2001, a pool filter manufacturer named B&S Plastics, Inc. (dba Waterway) recalled 19,500 filter systems after receiving at least three sudden disconnection claims. Waterway said, "Several instances have been reported of the upper half of the filter housing being ripped off the lower housing suddenly and without warning with great force." Waterway admitted, "These filters operate under a typical pressure of 15-25 psi. There is a possibility of serious injury if the upper half of the case detaches under pressure.”
Today, however, hazardous pool filters continue to be manufactured and sold without the available protections.
Product liability theories of liability
A product with a design defect or inadequate instructions subjects the manufacturer to strict liability. (To see,Wright gegen Stang Manufacturing Co.(1997) 54 Cal.App.4th 1218, 1228-1229.) A product has a design defect when the inherent risks of the product outweigh its benefits. 🇧🇷González v. autoliv(2nd Dist., 2007) 64 Cal.Rptr 3d 908, 913.) Risk-benefit tests include weighting factors such as (a) the severity of the hazard presented by the attacked design, (b) the likelihood of such a hazard (c ) the mechanical feasibility of a safer alternative design, (d) the financial cost of an improved design, and (e) the adverse product and consumer consequences that would result from an alternative design. 🇧🇷ibid.)
Evidence from other accidents may show that a product poses an unreasonable risk of harm; and the manufacturer knew or should have known about the risks of the product. 🇧🇷Benson v Honda Motor Co.(1994) 26 Cal.App.4th 1337, 1344-1345.) Once the plaintiff proves that the design of the product caused the damage, the burden of proving the absence of a defect falls on the defendant. 🇧🇷identity. em 914;Bernal v Richard Wolf Medical Instruments Corp.(1990) 221 Cal.App.3d 1326, 1332.)
Pool filters with weak clamping arrangements are design flawed because they present a predictable and significant hazard that would have been eliminated by a safer, more feasible and more practical alternative design.
• The severity and likelihood of an explosion
The potential for pinch failure and filter cover bursting poses a serious hazard to consumers. The explosions are predictable given the history of explosion problems.
The CPSC recognized this risk in the 1970s, and manufacturers understood this risk when one of their colleagues recalled more than 19,000 filters in the early 2000s, describing the risk of sudden separation as "a public safety issue." The collapsed filter comprised a tank with a top and bottom connected by a giant "lock nut" or bolt, as opposed to a multiple nut system. This manufacturer removed the filter because users reported explosions, including one that injured an eye.
Finally, the NSF/ASNI 50 standard requires an automatic vent valve on the top of a filter if air is allowed to collect in the filter tank. Many filters do not have an automatic vent valve in the cap. The lack of an automatic vent valve increases the likelihood of an explosion. Filters without an automatic vent still need to be fitted with more secure fasteners such as screws and wing nuts.
• The restraint system is susceptible to abuse and failure.
A common defense in these cases, as always, is "blaming the victim." Manufacturers report that homeowners over-tighten fasteners, which can weaken the threads of the fastener screws. Or the defense can argue that the victim did not stage the wiretapping. But these are circular arguments, since abuse is foreseeable.
Manufacturers know how easy it is for a layman to over-tighten or misalign components. Also, a product that can rip a user's head off shouldn't be as prone to common user errors.
• Fastening with bolts and nuts was technically and economically feasible.
Cable lugs and nuts are technically feasible, make economic sense and are safer than a clamp. Competing filter manufacturers used the design in Figure 4.
Handles and nuts would eliminate the risk of serious injury. If a tab or nut fails, the remaining tabs and nuts hold the top and bottom together. In the worst case, a nut failure would result in water leaking from the filter. A manufacturer's PMQ is likely to certify that there were no technological barriers to a nut and bolt system.
More questions and theories
There may be other causes of action besides asserting product liability against the manufacturer (or possibly the component manufacturer if a separately manufactured component of the restraint system fails).
Manufacturing defects can be traced back to processing errors (defective tack welding, defective thread, etc.) in terms of product liability; defective parts (wrong metal or cut) and the like. With claims of defective design, the filters often suffer from a weak seal, an unclean seal; or confusing instructions on the cuff assembly or pressure relief valve. Likewise, a design flaw can include an inadequate relief valve (valve too small to allow air to escape fast enough to release the pressure) or poor relief valve design.
If not notified, the user manual and other written materials often contain conflicting messages that confuse the user.
Don't overlook the negligence of the pool filter installer. These cases may include installing the filter isolator within the “danger zone” on deck or using penstocks that pressurize the system.
The authors wish to acknowledge that the Pool Filter cases were initiated by Attorney Kevin Lancaster at Veen Law Firm over a decade ago. Lancaster is a professor in his knowledge and skill with the technical problems in these cases, and his ability to explain complicated concepts of mechanics and physics to laypeople is legendary.
A successful example was his demonstration to an audience of defendants, defense attorneys and insurance adjusters, using a toy "water rocket launcher" that pumps air into a rocket partially filled with water. These $5 toys generate enough pressure that a child can launch the rocket several hundred feet in the air simply by pumping air into the chamber. This made it abundantly clear to the defense how effectively the jury would be educated on the concept of the dangerous pressure levels that can be created by the mixing of air and water in pool filters, and a very substantial agreement was soon reached.