Clad water connections with aerated concrete blocks

Hello,

I have to design the storage for my bathtub myself, and I plan to do this with aerated concrete blocks.
Now I am wondering how wide my blocks need to be at the water connections.
I have attached a photo - with a scale.
At first, I thought the entire connection had to be inside the blocks (so 20.4 cm), but I saw at my neighbor’s that the white piece (meaning another 7 cm) sticks out.
What is correct? Does it matter here in "mm" or "cm," meaning do I have to cut the blocks to size, or can I use standard sizes (there are 11.5 cm or 15 cm wide blocks)?

Thanks!

The things on top are the sealing plugs. If you brick them in, no water will ever come out.

Hello hello

The white parts are construction plugs. They are removed during the installation of the bathtub filler tap.
Your walling can be built up to 19cm like this.


Olli

You can also extend the connections relatively easily if you have built the wall too wide.