The exhaust systems are of two types: double-pipe, that is, with a double drainage system that keeps separate and black water from the white, or single-pipe in which both the black and the white water flow together.
The black waters are those coming from the toilet drain and the white water coming from the drain of sinks, sinks, washing machines and dishwashers.
The double tube exhaust offers the advantage of greater hygiene: since there are two separate pipes, it is not possible to return the black water or its unpleasant odor through the drains of the sinks, bidets and bathtubs.
The single-pipe drain is usually used in condominiums and large building complexes, where the bathrooms and kitchens of the apartments are superimposed.
Both pipes can be made of cast iron, stoneware or PVC for both the exhaust system. This last material is increasingly used, above all for the connection of the service appliances (sinks, bidets, tanks) to the main drainage columns.