Hemp, used in conjunction with a linseed oil-based jointing paste, is a traditional natural fibre material for sealing threaded plumbing joints on iron and brass pipework. The fibres are wound around the male thread in the direction of tightening and bedded into a coating of paste, where they swell on contact with water to form a long-lasting seal. While largely superseded by PTFE tape in modern UK plumbing under BS EN 751-3, hemp jointing remains favoured by some heating engineers for high-temperature gas and oil applications. The technique is regularly encountered on older London plumbing during refurbishment of heating systems and Victorian gas runs. Hemp is identifiable by its tan-brown fibrous appearance when a joint is disassembled. The combination of hemp and paste is suitable for slow-cure joints that may need to remain serviceable for many decades.
Hemp (plumbing jointing)
Traditional natural fibre used with linseed paste to seal threaded plumbing joints.
