Both the new house and the drainage pipe are designed by our bathroom.

The drainage pipes in the building are indispensable. It is inevitable that some vertical pipes will pass through the residents' houses, and so will the top floor. Because the drainage pipes must be ventilated up and down, otherwise the water will not flow down due to atmospheric pressure, so the drainage pipes must be connected to the roof for ventilation. There are two 10 cm drainage pipes in your bathroom, which may be poorly designed. The drainage pipe can be designed in the wall. I've seen water pipes pass through residents' bathrooms, but they are covered by a raised rectangular wall. At least there are no two bare thick water pipes ugly, and the area occupied by this' rectangle' should be deducted from your housing area, which means you don't have to pay for this area of the house, haha ... but this has to be discussed with the seller. good luck