For a water heater, 30l, I have a new fitting requires. You must be depressurized and held the bathtub outlet have a connection for meien shower. It took a lot of patience, but with Amazon under pressure armsturen I found it. The seller must respect me. DesBrausanschlusses referred to a Fachändler. I went to the hardware store with the fitting and have received a transition piece for single pair cents. Now everything fits.
