Sioux Chief 645QK9 5/16" x 5/16" PDQ Polypropylene Coupling

Sioux Chief 645QK9 5/16" x 5/16" PDQ Polypropylene Coupling

The Sioux Chief 645QK9 is a 5/16" x 5/16" PDQ coupling molded from polypropylene, built for quick, tool-free connections between small-diameter cold-water tubing runs. It is designed for use with copper, polyethylene, and PEX tubing, making it a practical transition fitting for point-of-use supply lines such as ice-maker and humidifier runs installed behind the wall or under a fixture during rough-in or service work. This coupling is intended strictly for cold-water applications and must not be used with vinyl tube. Manufactured in Mexico and packaged 60 bags to a case with one coupling per bag, the 645QK9 gives plumbers a lightweight, corrosion-resistant fitting for stocking service trucks that see frequent small-tubing repairs, appliance hookups, and rough-in transitions between dissimilar tubing materials.

Key Features

• Trade Size: 5/16" x 5/16" coupling sized for small-diameter cold-water tubing connections.
• Durable Construction: Molded polypropylene body resists corrosion and won't pit or scale like metal fittings, giving it long service life in concealed rough-in installations.
• Multi-Material Compatibility: Connects copper, polyethylene, and PEX tubing, allowing a single fitting to bridge dissimilar tubing materials on the same run.
• PDQ Coupling Design: Sioux Chief's PDQ configuration is built for a quick, straightforward tubing connection without additional hardware.
• Cold-Water Rated: Intended for cold-water applications only; the manufacturer specifies it should not be used with vinyl tube.
• Lightweight Polypropylene Body: Compact profile fits tight rough-in spaces behind walls, under sinks, and near appliance supply points.

Technical Specifications

• Trade Size: 5/16" x 5/16"
• Material: Polypropylene
• Tubing Compatibility: Copper, Polyethylene, PEX
• Water Temperature: Cold-water applications only
• Country of Origin: Mexico
• Packaging: 60 BG (60 bags per case, 1 coupling per bag)

Typical Applications

• Ice-Maker and Refrigerator Supply Line Connections
• Humidifier Water Line Connections
• Residential and Commercial Cold-Water Rough-In
• Copper-to-PEX or Copper-to-Polyethylene Transitions
• Small-Diameter Tubing Repairs and Replacements
• Service Truck Stock for Appliance Hookups

Why Sioux Chief?

Sioux Chief builds rough-in fittings that professional plumbers rely on for dependable, consistent performance across cold-water and DWV applications. The 645QK9 PDQ coupling extends that focus to small-diameter tubing work, offering a polypropylene fitting sized and packaged for stocking on service trucks and job sites where quick copper, polyethylene, and PEX connections are needed without introducing metal fittings that can corrode in concealed, damp locations.