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Pool equipment can explode, maim, kill

Three workers were injured late June when a pool pump they were working on apparently exploded. The accident happened early on a Tuesday afternoon at the Legend Oaks Apartments, located on Garfield Court in Kansas City, Kansas. 

Fire Department Deputy Chief Craig Duke said three men were working on the pool’s water pump when it exploded, and a pipe shattered. 

The men were taken to the hospital for evaluation after being soaked with chlorine and getting it in their eyes as well as inhaling toxic fumes. 

All three men are expected to make a full recovery

Lindsey Owens and her spouse are tenants of the apartment complex. According to Owens, the men were just getting the pool going for the summer season.

Her spouse was helping the property manager and a maintenance worker when a PVC pipe burst after an explosion, covering the men in chlorine. The property manager got chlorine in his eyes. The maintenance worker inhaled a lot of the chlorine, while Lindsey’s husband also inhaled the chlorine and cut his foot, requiring stitches. 

While it’s fortunate that no serious injuries were sustained, it would be useful to understand why the accident happened in the first place so that others can learn from the possible mistake. 

For example, what caused the explosion? Could it have occurred from mixing incompatible chemicals? What was the chlorination system? Was it really the pump, or some other equipment explosion or failure? We contacted the Legend Oaks Apartment Complex for more details but they declined comment.

One reason for an explosion at the equipment could have been due to mixing chemicals in an inline or offline erosion feeder.

For example, calcium hypochlorite and trichlor are, in the presence of water, chemically incompatible and explosive. 

Calcium hypochlorite will also explode with dichlor and water. 

It is important never to mix organic chlorine with inorganic chlorine. The reaction of an isocyanurate (dichlor, trichlor) with hypochlorite (calcium, lithium, sodium) can result in the rapid formation of nitrogen trichloride, which at high enough concentrations will detonate spontaneously with great violence.

All of these chemicals are sold as “pool chlorine” and it is therefore not an intuitive notion that they might be incompatible with one another. It’s unfortunate that the pool industry often sells these explosively incompatible chemicals side by side because many consumers are not aware that what seem to be innocuous pool chemicals are in fact explosive when combined.

Another explosion risk is the use of fast-dissolving chlorine in automatic chlorinators designed for slow-dissolving chlorine. The fast-dissolving forms will break down too fast, causing too much pressure in the container. The pressure build-up can blow the chlorinator apart.

Furthermore, exploding filters are not unknown. Some manufacturers make a split-ring design so that the filter can be taken apart for cleaning and maintenance and put back together with the top half of the cylinder sitting on top of the bottom half, secured with a fastener belt.

Sometimes, the top half is accidentally seated imperfectly on the bottom half without a good seal and then secured with the fastener belt.

When the pump is turned on, pressure builds up, and the top half blows off. If an unsuspecting person is standing over the filter when this occurs, it can be fatal. 

One of the most well known examples of this was made public by Sue Halverson, after she started a website to inform the public about the danger of a particular pool filter design. Sue’s husband Jim was killed by an exploded filter in September 2006 when the pool filter’s pressure valve failed.

Numerous similar incidences have occurred both before and after this event. When air accumulates in the filter, enough pressure can build up inside to blow the top off. Accidents like this happen for a variety of reasons, including a lack of air relief valve, a failed air relief valve, an inadequate fastener belt or badly positioned fastener belt, and unreliable or broken pressure gauges.

These days, exploding pool equipment is rare because manufacturers have improved designs that prevent most injuries. Modern filters have been redesigned to be safer with sturdier clamp bands or held together by a series of bolts.

However, there is still a lot of older, unsafe equipment installed on pools, and many people are unaware of the danger.

It is also possible for a saltwater chlorine generator to explode. The gases that are generated in the generator are flammable and a build-up can be explosive. 

That is why chlorine generator manuals explicitly state that operating a chlorine generator without water flowing through the cell can cause a buildup of flammable gases, resulting in an explosion.

In normal generator operation, the water flow pushes the gas into the pool where it harmlessly bubbles out. However, if the cell is on without flow, hydrogen gas will accumulate at the highest point above the cell and if provided with a source of ignition will combine with oxygen explosively. 

For this reason, chlorine generators have flow sensors that won’t allow the cell to operate without water flow. In some cases, however, the flow sensor is not installed properly, which can allow the cell to operate without water. For example, the orientation of the cell is important to avoid a buildup of flammable gases. 

Furthermore, the location of the flow sensor with respect to the cell is also important. There have been cases where pool builders plumbed the flow sensor in inappropriate locations, such as between the pump and the filter rather than right before the generator. In this configuration, if someone were to vacuum the pool to waste with the generator on, the flow sensor would indicate water flow, but the cell would actually receive none, posing a real danger.

There was one case of a saltwater chlorine generator explosion that occurred while someone was servicing a filter. The cell had been installed with cell bypass valves so that it could be removed during the winter. The flow sensor had been installed outside of the bypass. While backwashing the filter with the bypass valves closed and the generator on, the cell exploded. Fortunately no one was injured.

The explosion possibilities presented here are certainly not an all inclusive list. There are numerous reasons that equipment explosions can occur, and it is important to be aware of them so that unexpected incidences do not occur. 

It is also a good idea to inform your customers should they get the urge to service their pools behind your back.

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