Preparation for photovoltaic or solar thermal with air-water heat pump

...Photovoltaics make much more sense with an air-to-water heat pump, and the preparation is significantly cheaper.

That is also my opinion.
However, the impression in the original post to route the solar thermal system preparation through the wastewater ventilation seems borderline to me.

What exactly do you mean by that?

I already understand which part of my post you mean, but what concerns do you have about it?

Apart from my concerns, wastewater vents have a function to fulfill (pressure equalization). Therefore, no interventions of any kind are permitted here, which also applies to so-called "automatic pipe vents." Even reductions in cross-section are not professionally correct and therefore not allowed! Regardless of whether it is a solar thermal system or photovoltaic system preparation, wastewater ventilation is fundamentally off-limits!

Oh, maybe that was just my interpretation of the conversation with the employee of my [GU]? Maybe it is not laid inside the pipe, but with the pipe. I think there is possibly still space next to the ventilation pipe (DN100?) in the shaft. I actually consider our [GU] to be very reputable and technically proficient....