The S-trap, invented by Alexander Cummings in 1775, prevents sewer gases from entering indoor spaces and remains a key feature in modern toilets.

Alexander Cummings patented the S-shaped pipe under the toilet basin, which uses a water seal to block foul odors from escaping the sewage system. This innovation was critical to the development of sanitary and odor-free indoor toilets, marking a turning point toward the modern flush toilet we recognize today.