If you want to add a bathroom, you need to go into the water. The diameter of sewer pipe is relatively thick, so it needs a certain slope (generally 5 degrees). This requires heightening the ground to solve this problem. Generally, it should be 150 mm, and then punch holes in the wall from the low end, so that the pipes can enter the bathroom. However, the added toilet can only be used for bathing, which can solve the problem of urination at most, but can not solve the problem of defecation.