A swimming pool filter can kill or maim you because it operates under pressure and can explode. 

A swimming pool filter cleans water of debris. Generally, there are three types of swimming pool filters: cartridge filters, diatomaceous earth (DE) filters and sand filters. All three types of filters operate under pressure, which creates the risk of explosion or “sudden separation” of filter parts.

A cartridge filter uses cartridges to trap debris as water flows through the filter. A cartridge filter typically consists of a two-piece container made from fiberglass or steel. The two pieces—a bottom and a lid—are fastened together to form the shape of a stout missile. Manufacturers equip cartridge filters with different types of fasteners. Some fasteners—such as bolts or inter-locking pieces— do a better job of securing the lid to the bottom than others. These fasteners provide a “positive means of attachment” and ensure that the lid will not blow off under pressure. Inferior fasteners—such as a clamp—can break under pressure or bend over time and allow the filter lid to blow off with tremendous force.

A DE filter—also housed in missile-shaped steel or fiberglass—uses diatomaceous earth, or fine earth composed of algae cells which contains silica. Grids inside the filter are coated with DE, which acts like a screen and traps debris as water flows through the filter.

A sand filter uses sand to collect and attract debris. The filter extracts the debris as clean water flows back to the swimming pool.

Click play to see video of an exploding pool filter.