Up to now, products protecting against water penetration have mainly been installed inside buildings. In the meantime, however, new methods are being pursued. The idea is to not let any wastewater into the house in the first place, then you won't have to keep it back there.

For this purpose, an inspection chamber housing the backwater valve is installed outside the building. The base pipe which is used exclusively to drain spots in danger of backwater, is backed up by this backeater valve.
The inspection chamber has other pipe connection possibilities that are not routed through the backwater valve. Those base pipes that are responsible for drains not endangered by backwater are connected to these.

Ideally, this chamber is built in when a land-use area is being developed. Then the right backwater unit can be installed later as required.