Everybody who wants to build up a new house or renovate an old building today, often require a barrier-free bathroom with a walk in shower area. While this is pretty easy to implement in a new building, there could be some obstacles when a bathroom in an old building should be modernized. Especially in old buildings the floor installation heights are often very low. So without enough impounding depth the shower water cannot drain. The slope is not sufficient enough to transport the sewage to the next downpipe.
The easy exchange of the old shower tray for a conventional flat shower drain is usually impossible due to the floor foundation. In case of removal of the old floor screed and insulation, the incidental shower water must flow against the flow direction to reach the available gravity downpipe. A physical limitation that cannot be ignored.