Putting It All Together

Now that you have seen all the parts, you can understand the complete mechanism:

  • Pushing on the handle pulls the chain, which releases the flush valve.
  • About 2 gallons (7.6 L) of water rush from the tank into the bowl in about three seconds. The flush valve then reseats.
  • This rush of water activates the siphon in the bowl. The siphon sucks everything in the bowl down the drain.
  • Meanwhile, when the level of the water in the tank falls, so does the float. The falling float turns on the refill valve.
  • Water flowing through the refill valve refills the tank as well as the bowl. As the tank refills, the float rises, and when it reaches a certain level the refill valve shuts off.
  • Should something go wrong and cause the refill valve to keep running, the overflow tube prevents a flood.

­What happens after it flushes? Read How Sewer Systems and Septic Tanks Work for a complete rundown.