American Standard Champion Toilet - How to tell if your Flush Valve is less prone to leaking (old-new photos)
Posted by Al L on January 28, 2004 at 00:15:31:

American Standard has changed the Flush Tower detail by cutting back the flange above the silicone seal. The seal now suspends the tower when the valve is closed. This appears to let the seal conform better to irregularities. For those not familiar with the problem, the original flush towers leak intermittently. This may cause the fill valve to turn on every 15 minutes to every 6 hours. If your toilet is used more frequently than the refill rate, you may never notice the flush valve leak. A subtler symptom of the problem is a weak flush caused by the lower water level.