Troubleshooting Pneumatic Toilet Flush Valves, Buttons and Plates
Pneumatic toilet flush valves are a simple and generally reliable type of flushing mechanism.
These valves work by squeezing air into one or two "bellows" which expand and in turn lift the flush valve and release the water in the toilet cistern.
The push button or flush plate also usually contains one or two of these bellows. Alternatively the button or flush plate may contain one or two piston mechanisms. When one of the buttons is pressed, this squeezes one of the bellows or pistons inside and provides the necessary air pressure to inflate the bellows inside the flush valve and lift it. Once the button is released the bellows return back to their normal state and the valve drops, sealing the cistern.
Over time as the toilet is continuously flushed, parts of this mechanism can fail.
Troubleshooting this type of mechanism is usually quite straightforward and rarely requires replacing all of the components.
How to Troubleshoot:
1. Disconnect the pneumatic tubing from the rear of the flush plate or button. The tubing usually just pushes onto one or two "spigots" on the rear of the push button or plate. Take care not to snap these off when removing.
2. Blow down the pneumatic tubing that has now been disconnected from the button or plate. If the flush valve lifts and empties the cistern, then there's an issue with your push button / plate or the bellows within it. If the flush valve doesn't lift, then the bellows in the flush valve will likely need to be replaced.
There are only a few push buttons and plates on the market which have serviceable bellows inside of them, the vast majority are sealed units. As such a full replacement push button or plate will likely be required if the button or plate is faulty.
Many pneumatic flush valves have serviceable bellows or "activation units" attached to them. Usually only in exceptional cases a full replacement flush valve is required, for example if part of the housing has snapped or it is jamming in some way.