Train toilets have greatly evolved. The features provided (hand dryer, soap dispenser, baby-changing table…) are more and more numerous. And over the 3 different generations of toilets (open toilet bowls over the rails, chemical toilets, clean water toilets), the effluent evacuation and storage systems have improved to create trains that pollute as little as possible. Clean water tanks (or blue water tanks for chemical toilets) are used to supply the toilet bowl and the taps. And tanks of grey water and effluents make it possible to store wastewater until it is emptied in the station.