So we also have a 4-way multi-duct with the following assignment. Gas, electric, and telecom. Water also goes through this separate flexible hose with us, as it does with you. So we still have one free. Additionally, we have a 100mm flexible pipe from the house to the garage where currently a 16mm^2 electric cable, 2x LAN, and a coaxial cable are laid.
We paid around €800 for the multi-duct.