Charlotte Pipe 1/2 in. PVC Schedule 40 S x S Coupling PVC021000600HD - The Home Depot
Amazon.com: 1/2 NPT Male to 1/2 NPT Male Straight 316 SS Hex Coupler/ Coupling for Air, Liquid or Hydraulic Fitting - Industrial Air Tool Hose 1/2 Inch Coupling 316 Stainless Steel : Industrial & Scientific
560-09 Borit Reducer Coupling - 1/2 to 3/4 inch - Borit Manufacturing
Horiznext npt 1/2 (means the inner diameter of the thread is 3/4 inch) cast female taper threaded pipe coupling, stainless steel 304 coupler for mush tun cooler and shower hose, 2 pcs - Amazon.com