The western toilet is designed so that it flushes once in a continuous flow after a person uses it. This ensures that any excrement is washed away. However from a fiqhi perspective it is known that for urine a object must be washed twice with a break(water stops flowing) in between washing. If one flushes a toilet which only leaves one continous flow is the water after the flushing considered najis?

The water inside the toilet bowl is najis once the water stops flowing. The reason is the fact that it is connected to a P-trap, which is not pure. Although you don’t see what’s in the P-trap if you study hall toilet work, you will understand that the P-trap area is always going to have remnants of najasah