Exploding Filters
All types of swimming pool filters operate under pressure. If air is trapped in the filter and not released the air will continue to compress while the filter is operating. Small amounts of air can work its way out of the filter but large amounts will compress to a dangerous level. When this occurs the filter may blow apart. Also, if a retaining ring is not seated properly or if the tightening band fails this can happen. Pressure build up from a filter not being cleaned can also build dangerous pressure. During pollen season it is imperative to check the filter pressure often. Serious injury and death has occurred from an exploding filter.
Most filters will have an air release mechanism that needs to be opened when the system is turned off and also left open when starting the system until a steady stream of water comes out through the mechanism indicating that the air has been removed from the tank. It is of the utmost importance to use this feature.
For filters that have a retaining band (clamping) with a bolt that tightens the band it is necessary to be sure the washer remains in place so that the bolt cannot slip and allow the top half of the tank to become a projectile when pressure builds within the unit. This band and tightening mechanism also needs to be replaced if it has rusted or corroded as it could also be compromised.
With units that are connected with a tightening band or a “posi-lock” band (threaded like a mason- jar ring) it is very important to be sure that no dirt or debris is present in the area where the two halves are connected as this could also cause a failure. Be sure that the halves are seated properly and fully seated when re-assembling. Inspect the locking band for hairline cracks or ruptures on a regular basis.
In 2004 a recall was issued by the Consumer Protection Safety commission on some Sta-Rite and Aquatools brand filters. These filters were manufactured from January 2003 – October 2003. For more information see:
When high pressure builds in some filters that are banded or bolted in the middle of the tank a leak may develop from that area due to the high pressure. If this occurs turn the system off, wait a few minutes and carefully open the air relief valve allow the pressure to escape. After the pressure has been let out of the system, start the system up and allow a steady stream of water to escape from the air relief valve before closing it. Be sure that all valves are in the open position allowing the water flow to enter and exit the pump and filter. Backwash or clean the system as that can cause building pressure as well.
Again, regular inspections can prevent this dangerous situation.
Comments
Where the danger lies is in a faulty closure, or improper opening and closing. I agree the filters are designed to handle more pressure and many times work the air out. However, if there is a fault in the closure of system or the air is not released when opening or re-starting the system a dangerous event can occur. As figures are concerned, the lawyers seem to have multiple cases and I have not seen any per say figures. This is something that I believe more education in our industry and to the public should be emphasized.
Wendy, can you give any figures to the "dangerous pressure" Air is compressible but as the system pressure is only roughly 1.0 bar and most filters are capable of handling far more.