Toilet water tank - flushing

Sound of flushing toilet and refilling the water tank. This water tank is a bit older version as it has just one push button.
When water flushes, the cistern has to refill automatically from a kind of faucet on the side and the refilling operation has to last just long enough to fill the tank without making it overflow. Some water stays trapped in a big curved pipe at the base of the toilet known as the S-bend (or S-trap). This water effectively seals off the sewage pipe beneath it, stopping germs and bad smells from coming up. The S-bend also means that the pipe running out from the toilet bowl curves upward, before curving back down again. That means when water flows into the bowl from the cistern, and drains out through that pipe, it has enough momentum to produce a siphon (sucking) effect, which properly empties the bowl.