Is there a place on Toto toilets where it says the model or gives a model number?

Is there a place on Toto toilets where it says the model or gives a model number?

Someone I know has 6 Toto toilets for about 4 years. In that time they have had to
replace the flapper in 4 or 5 of the toilets. She uses clorox tablets in her tank.

Can this be causing the flappers to go bad?
Thank you.

Chlorine voids warranties on all brands.

Look inside the tank, and there should be CSTxxx stamped in the back. The last three will be numbers.
As long as she keeps melting the rubber parts with Chlorine, the flapper companies will be making out well.

For what it's worth, if your friend is addicted to bowl cleaner, I know that Fluidmaster makes a container that the refill hose goes into and a hose down the overflow stack comes out of, in which people can put Fluidmaster bowl cleaner. That way, the liquid in theory bypasses the flapper (although you now have concentrated cleaner running just under the flapper and maybe getting on it, so I'm not convinced that this setup is perfect). Here's the link: Fluidmaster Flush and Sparkle.

I don't know if any of our pros have any experience with or thoughts about this product, but I'm assuming that it can't be worse than what she's doing now.

PS Four years is pretty amazing for those flappers to last with Clorox tabs in the tank. I think I saw a picture of a Toto pink flapper that maybe Terry posted that had been melted very quickly after the customer had started using bleach tablets.