Pentair 21" Bottom Tank Half Kit

The Pentair 21" Bottom Tank Half Kit (Part #24850-0102S) is a structural replacement pressure vessel base designed specifically for 21-inch diameter Sta-Rite System 3 pool and spa filtration systems. This structural shell is fully compatible across multiple System 3 configurations, including the Modular Media SM-Series, the Modular SMD/SD Series Diatomaceous Earth (D.E.) filters (such as Model S7D75), and the SS-Series Sand Filters (such as Model S7S50).

Injection-molded from a high-impact, fiberglass-reinforced composite resin, this lower shell is engineered to endure harsh outdoor weather, high-exposure pool chemistry, and continuous internal hydraulic pressure loops. It features specialized, molded-in connection ports designed to seamlessly receive internal collection manifolds, bulkhead plumbing adapters, and integrated drainage plugs. By acting as a standalone baseline replacement, it enables pool technicians to swap out a fractured, cracked, or leaking filter basement without necessitating the purchase of a completely new filtration system.

Weight Profile

Given its heavy-walled, high-capacity commercial and residential infrastructure, this lower tank shell carries a substantial physical footprint:

• Actual Product Weight: Approximately 25.0 to 30.0 pounds.

• Packaged Shipping Weight: Typically scales at 42.15 pounds due to the heavy-duty, highly insulated box volume (measuring roughly 30.5" x 30.0" x 26.0") required to safely transport the broad composite dome without warping, scratching, or flexing during transit.