Bullhead Tee, Slip x Slip x Slip PVC Schedule 40 4" x 4" x 8" (401-428)

The 4" x 4" x 8" PVC Schedule 40 Bullhead Tee (Slip x Slip x Slip), Part #401-428, is a purpose-built large-branch tee fitting where the 8-inch branch outlet is double the nominal diameter of each 4-inch run port — an extreme size differential that makes this one of the most hydraulically distinctive configurations in the PVC Schedule 40 bullhead tee series. Manufactured from Type I, Grade I PVC compound to ASTM D2466 specifications, this fitting delivers reliable pressure performance, broad chemical resistance, and long service life in the specialized flow collection, pump manifold, and aggregation header applications that bullhead tee geometry is specifically designed to serve.

The bullhead tee configuration inverts conventional tee logic: rather than a dominant flow moving along the run with a smaller branch takeoff, the bullhead tee is engineered for applications where the branch carries the primary or combined flow and the run ports serve as collection inlets or distribution outlets. At the 4" x 4" x 8" size ratio, this inversion is particularly pronounced — the 8-inch branch has four times the cross-sectional area of either individual 4-inch run port, making this fitting purpose-suited for applications where two mid-size supply lines must combine their total flow volume into a single large-diameter discharge, or where a primary 8-inch supply must split into two independent 4-inch distribution circuits simultaneously.

The most common use case for this specific size combination is pump suction manifold and collection header design. The two 4-inch run ports aggregate flow from upstream supply lines, storage tanks, or parallel distribution circuits, delivering the combined volume through the 8-inch branch to a pump suction inlet, filter housing, or primary distribution main. The doubling of nominal diameter from run to branch at this ratio means that, under ideal flow conditions, the velocity entering the 8-inch branch is significantly lower than in either 4-inch run — a favorable hydraulic characteristic for pump suction applications where minimizing inlet velocity and turbulence at the suction port improves pump efficiency and reduces cavitation risk.

In reverse-flow configurations, the 8-inch port functions as the primary supply inlet, simultaneously feeding two independent 4-inch distribution circuits from a single larger-diameter source — a design encountered in irrigation distribution manifolds, treatment plant process headers, and industrial utility systems where a single large-diameter supply must be divided into parallel mid-size circuits without a fabricated manifold assembly.

The slip x slip x slip (plain end) configuration accepts solvent cement across all three ports, producing permanent, chemically bonded joints at all connections. Installation orientation relative to dominant flow direction is critical with bullhead geometry — the 8-inch branch port should be aligned with the primary flow direction in the system, and hydraulic design must account for the significant velocity and pressure changes associated with the two-to-one nominal size ratio between run and branch.

Specifications:

Note: Pressure rating decreases with elevated temperatures and is further influenced by dynamic flow conditions at the branch junction. The 4" x 4" x 8" bullhead tee geometry — where branch diameter is double the run diameter — introduces pronounced flow dynamics including turbulence at the branch junction, potential recirculation zones, and velocity changes that are more significant than in bullhead configurations with a smaller run-to-branch differential. These factors should be carefully accounted for in hydraulic design, pump sizing, and system pressure calculations. The favorable low-velocity characteristic at the 8-inch branch in collection-flow applications makes this fitting particularly well suited for pump suction use, but suction line design should still follow accepted engineering practice for NPSH (Net Positive Suction Head) requirements. Consult ASTM D2466 derating curves and applicable engineering specifications before installation in high-pressure, high-velocity, or continuously pressurized service.

Industries & Applications:

• Pump Suction Manifolds — Aggregating flow from two 4-inch supply lines into a single 8-inch pump suction port — the defining application for this size combination, where the doubling of nominal diameter from run to branch produces lower inlet velocity at the suction port, reducing turbulence and cavitation risk while simplifying pump station manifold design with a single purpose-built fitting rather than a fabricated multi-component assembly.
• Irrigation & Agricultural Systems — Collection manifolds and pump station suction headers on large-scale irrigation systems where two 4-inch zone supply, storage tank outlet, or well discharge lines must be aggregated into a single 8-inch pump suction, filter inlet, or mainline feed at a pump station or booster station assembly.
• Water & Wastewater Treatment Plants — Process manifolds, filter influent headers, recirculation pump suction assemblies, and chemical feed system collection points where multiple mid-size process lines must converge into a single larger-diameter equipment connection or process header.
• Municipal Water Infrastructure — Collection headers and aggregation manifolds in water utility systems where two 4-inch service or supply feeds must combine into an 8-inch transmission or distribution main connection, particularly at pump stations, storage tank outlets, and booster station suction assemblies.
• Industrial Process Piping — Flow aggregation in chemical processing, manufacturing, and plant utility systems where two parallel 4-inch process supply lines converge into a single 8-inch primary circuit, discharge header, or equipment connection — eliminating the need for a fabricated manifold assembly in space-constrained mechanical areas.
• Aquaculture & Recirculating Systems — Recirculating aquaculture system (RAS) pump suction and collection manifolds where drain or return flow from multiple 4-inch tank circuits aggregates into a single 8-inch pump suction or filtration system inlet, and where the low-velocity characteristic of the larger branch port is particularly beneficial for minimizing turbulence at the suction connection.
• Fire Suppression & Water Storage Systems — Tank outlet and supply aggregation manifolds where two 4-inch storage tank outlets or gravity feed lines combine into a single 8-inch fire pump suction, gravity distribution main, or booster pump supply connection.
• HVAC & Mechanical Systems — Chilled water and condenser water system collection headers where two 4-inch branch return circuits must combine into an 8-inch primary return main or chiller inlet connection at a central mechanical room manifold assembly.
• Mining & Aggregate Processing — Dewatering pump suction manifolds and process water collection headers where multiple 4-inch pump or sump discharge lines aggregate into a larger 8-inch primary discharge circuit in corrosive or chemically aggressive operating environments.