Two of my toilets are of the same model. Both are made by American Standard and both use the flapper as shown in the following link:
Lowe's sells this flapper for around $9. Here, I need to pay more than $30 for it.
About three months ago, one flapper would not come down after flushing. I thoroughly cleaned it and then put it back. It started to leak. I tried many things but ended up buying a new one.
Now, the other toilet has the exact same problem. Yesterday, I was informed that the flapper would not come down. I went to check it. It was not leaking at that time. I removed the flapper and cleaned it. After I put it back, it started to leak, just like the other one. I used a toothbrush and a plastic brush to clean. They should not damage the flapper.
Can anyone explain why a flapper which was not leaking leaks after cleaning? Much appreciated.