John Guest, a Reliance Worldwide brand, produces push-to-connect plastic and brass fittings used in plumbing, water filtration, and beverage applications. Its Speedfit and ProLock connectors are a quick-install standard for water filtration and PEX-based plumbing.

Johnson Controls is a global building-systems supplier whose HVAC brands include York, Coleman, Luxaire, and Tempstar. The company also makes building automation, fire and security, and refrigeration controls used across commercial and industrial buildings.

K-Rain Manufacturing produces irrigation rotors, valves, and controllers for residential and commercial sprinkler systems. The Florida-based brand competes with Hunter, Rain Bird, and Toro across the irrigation distribution network.

Kallista, a Kohler Co. luxury brand, designs handcrafted bath and kitchen fixtures including faucets, lavatories, tubs, and shower fittings. Its collections, often by named designers, target the high-end residential and yacht markets.

King Innovation makes irrigation accessories including DryConn waterproof wire connectors, valve boxes, and tools for splicing and installing low-voltage controls. Its waterproof connectors are standard issue for irrigation contractors.

Kohler Co. is one of the largest plumbing manufacturers in the world, producing toilets, sinks, faucets, baths, showers, and accessories under the flagship Kohler brand and luxury offshoots like Kallista and Robern. The Wisconsin-headquartered brand sets benchmarks across kitchen and bath.

Laars Heating Systems, a Bradford White company, manufactures residential and commercial boilers and water heaters including the Mascot, Mighty Therm, and NeoTherm product lines. The brand is widely specified in hydronic heating, snow-melt, and pool-heating applications.

Lasco Fittings manufactures Schedule 40, 80, and DWV PVC and CPVC fittings for plumbing, pool, irrigation, and industrial applications. The Tennessee-based maker is one of the largest U.S. PVC fitting producers.

Lavelle Industries, the maker of Korky, produces toilet repair products including flappers, fill valves, flush valves, and supply lines. Its Korky line competes directly with Fluidmaster across the toilet repair aisle.

Lenova Sinks designs and manufactures stainless steel sinks for kitchens and bars, with deep workstation-style configurations and integrated accessories like cutting boards and colanders. The brand competes in the chef-kitchen and luxury residential market.