Backflow is something that needs to e considered when maintaining your home. As a home inspector, it is something that can come up on a home inspections at times. It can also contaminate your water supply. So why does it happen?
Ultimately, there are two main reasons as to why this might occur;
Back-Siphonage – Caused by negative pressure in the supply piping, back-siphonage will see a reverse in the normal direction of water flow actually within the piping system. Essentially, this means that a vacuum or even a partial-vacuum leads to a reversal in the normal flow. Although it mainly occurs because of high velocity in the pipe line, it can also happen as a result of a line repair or break below the service point. Finally, a lowered main pressure will cause the same problem.
Back-Pressure – Rather than being caused by negative pressure, back-pressure is a reversal in the normal flow thanks to the downstream pressure overwhelming the supply pressure. Normally, this drop in supply pressure will occur when the amount of water being used far exceeds the amount being provided. For example, this is common during fire-fighting or water-line flushing.