Pipe plumbing.

 The diagram illustrates a typical plumbing setup for a bathroom, showcasing the connections between the sink, toilet, and the main drain line. It likely aims to guide DIYers or plumbers in understanding the basic layout and pipe sizes involved.

* Sink: Represented by a simple basin shape, the sink is connected to a 40mm (1-1/2 inch) drain pipe. This pipe then joins the main drain line. 

* Toilet: Depicted as a simplified bowl, the toilet has a larger 50mm (2 inch) drain pipe due to the larger volume of waste it handles. This pipe also connects to the main drain line.

* Main Drain Line: This is the primary vertical pipe that collects wastewater from the sink, toilet, and potentially other fixtures (not shown in the diagram). It is labeled as "Магистральная ветка" in Russian, which translates to "Main Branch". 

* Main Stack: This is the vertical pipe that the main drain line connects to. It is labeled as "Основной стояк" in Russian, which translates to "Main Stack".

* Ventilation Pipe: A smaller pipe labeled "Вентиляция" connects to the main drain line. This is a crucial element in plumbing systems, as it allows air to enter the drain line, preventing siphoning and ensuring proper drainage.

* Фанový выход: This label likely refers to the vent pipe connection point.

Pipe Sizes and Connections:

* The sink drain uses a 40mm (1-1/2 inch) pipe.

* The toilet drain uses a 50mm (2 inch) pipe.

* The main drain line appears to be a larger diameter pipe, likely 110mm (4 inch) based on the label.

Additional Notes:

* The diagram uses Russian labels, which might require translation for some viewers.

* The diagram is simplified and doesn't show all the details of a real plumbing system, such as traps, cleanouts, or specific fittings.

Overall, this diagram provides a basic overview of the plumbing connections for a sink and toilet. It is a helpful visual aid for those interested in understanding the fundamental layout of a bathroom plumbing system.