The cistern of our on suite toilet kept running.
I typed in “Caroma Cistern Valve” in YouTube search bar, and watched.
I then, armed with grips, pliers and scissors (yes, scissors. Reason will become apparent) and took apart the cistern valve (removed float, arm, adjustedment screw, level, anchor collar). Lo and behold, the gasket on the threaded pipe was disintergrated, and the rubber washer on the valve stop was no longer ‘springy’ enough to lift the floatation arm to the shut off point.
Hmm, I didn’t have any washers or gaskets handy, so this is where the scissors come in. I got a rubber band, the same thickness as what was left of the original gasket on the threaded pipe. Bevel cut, so the cut ends would rest against each other. Then I got waterproof bandaging tape, and cut about a 1cm piece. Folded it in half, so the sticky sides faced each other. Then cut it to the size of the rubber washer on the valve stop.
Reassembled valve. Replaced floatation arm. Turned the water on. Waited until the water got to the level line and adjusted the screw until the water stopped filling. And it stopped filling without continuously running. Then I noticed I forgot the anchor collar. I will put it back only if I see there is a problem without it. On a nifty aside, I probably saved the household $300 in parts and labor getting a plumber in here to do it.