Plumbing is the system that brings water into the home and takes it back out. Some plumbing projects require specialized tools to complete the job. You have to find the problem before you can fix it.
It is best to familiarize yourself with your home supply and drainage system. These two must always be two distinct subsystems with no overlapping. One subsystem brings freshwater in and the other takes wastewater out. The water that comes into your home is under pressure. It has enough pressure to allow it to travel upstairs, around corners and everywhere else it is needed. As it enters your home it passes through a meter which registers your water consumption. The main water shut off valve is located close to the meter.
Drainage systems do not depend on pressure, as supply systems do. Instead, waste matter leaves your house because of the drainage pipes all pitch, or angle, downward.