PVC unions are four part fittings, comprising two solvent weld sockets, a union nut and an O-ring. Unions are a type of coupling, in that they join the plastic pipe together in a straight line. Unlike a plain PVC socket, however, the unions allow the operator to take the pipe apart and put it back together again, by unscrewing the union nut. Unions are often used either side of pieces of equipment such as pumps, flow meters, filters etc. which allows the equipment to be quickly taken apart and reassembled for inspection, servicing or replacement, even in wet conditions. PVC pipe of the same size category is solvent cemented into each side. The PVC unions have a pressure rating of greater than 10bar and are fully WRAS approved for use with drinking water. Unions are sold up to 4"/110mm in size - for pipe sizes larger than that, flanges will be required.