The water in the toilet flush tank will flow back into the water pipe when the water stops, what can

Yes, there may be cases where water from the toilet tank flows back into the mains. Under normal circumstances, the water in the toilet tank does not flow into the water supply pipe, because the pressure lever in the tank automatically crushes the valve when the water is full, preventing backflow. However, if the toilet bowl has been used for a long time, the valve is easy to break if it has been used for too long. >>>More

It is caused by the high level of the flush toilet and the low level of the tap water.

Under normal circumstances, the water in the toilet tank does not flow back. Because the pressure rod in the tank will automatically crush the valve when the water is full, preventing backflow. >>>More

Adding a check valve to the water outlet means that the water can only come out, not pour it back

Is it really blue? It can't be that the water is too clear! If it's really blue, and it's always been blue, then you need to find out.