Pentair 12.5" Replacement Lid Posi-Clear RP® Cartridge Filter 150 - 200 Sq Ft

The Pentair 12.5" Replacement Lid for Posi-Clear RP® and Clean & Clear® RP Cartridge Filters (part number 178745Z for the Posi-Clear RP line; cross-compatible with the Clean & Clear RP equivalent 178546Z) is a highly specialized internal containment shell engineered exclusively to seal the upper pressure chamber of mid-to-high capacity 150-square-foot and 200-square-foot single-cartridge pool and spa filtration systems.

Injection-molded from thick-walled, fiberglass-reinforced polypropylene composite, this 12.5-inch diameter dome serves as the primary structural cap for the filter vessel. Its primary operational role is to close off the top access chamber, seating tightly over the main tank body O-ring beneath a specialized heavy-duty locking ring. This creates an absolute watertight and airtight compression boundary, allowing the single-element filtration system to maintain its high-efficiency hydraulic flow pattern while safely sustaining continuous internal operating pressures up to 50 PSI without weeping, flexing, or risking structural blowout under intense pump vibration surges.

The crown of the lid features precision-threaded interface ports designed to house the filter's external system pressure gauge and the High Flow™ manual air relief valve assembly. This ensures technicians can cleanly bleed trapped air pockets from the absolute highest pressure zone of the tank core during start-up cycles. Engineered to withstand decades of demanding outdoor equipment pad weathering, direct UV exposure, and intense seasonal temperature shifts, its rugged composite framework completely resists material structural degradation, cracking, and chemical bleaching from direct contact with highly concentrated sanitizers like chlorine, bromine, and winterizing acid flushes. Due to its thick-gauge, reinforced plastic structural dome profile, this individual replacement tank lid carries a net product and shipping weight of approximately 5.00 to 5.50 pounds (about 80 to 88 ounces).