crwdns2936637:0crwdne2936637:0 crwdns2853008:0crwdne2853008:0 crwdns2918746:0crwdne2918746:0

crwdns2944351:0crwdnd2944351:0Toilet Flush Valve Seal Replacementcrwdnd2944351:0crwdne2944351:0

crwdns2933797:0M J McAllistercrwdnd2933797:0crwdne2933797:0

crwdns2936047:0crwdne2936047:0

crwdns2933769:0crwdne2933769:0
crwdns2933771:0crwdne2933771:0
crwdns2933801:0crwdne2933801:0
Conclusion
Flush Valve Seals will need to be replaced, at least, once every few years, depending on water condition. Other kinds of toilet water tanks may have similar assemblies. Why call a plumber for something so easy to do yourself?!