Double drain system (DDS)

If you opt for a system without a waterproof top layer (broadly speaking, all installations where a waterproofing mat, liquid rubber, etc. is used). The most common of these is a tiled shower consisting of tiles and joints. In this case, it should be borne in mind that a joint is only 80% waterproof. This means that 20% of the water that falls on the joints permeates the joint and penetrates underneath the tiles and the waterproofing mat. If the joints are damaged or worn, that percentage is much higher.

The DDS system is not a second siphon! The function of a siphon is only to cut off unpleasant smells, which is why it is often referred to as a trap.

The DDS system means that both the water that falls on the tiles and the water that permeates through the joints and is captured by the waterproof mat is directed to the drain. (see illustration)

For shower drains without a DDS system, only the water that falls onto the tiles runs down the drain, and not the water that permeates the joints. e.g. shower drains with a raised flange (see illustration)