PPGSC-20 3/4" GALV COUPLING | The galvanized merchant coupling is used to repair pipes, these come with a pre-welded coupling onto the pipe and are used to repair pipe needing a weld. Also suitable for hot and cold water systems, refrigeration, sprinklers, compressed air, gasoline, diesel, alcohol, and some other applications where conducted fluid needs inner rustproof protection. The black pipe fittings are used in connecting black pipes, which are ideal for transporting gas, oil, air in urban, and rural areas