I noticed a little amount of dirt at the bottom of the tank. None of which makes its way into the bowl. I completely cleaned out the tank and when I filled it back up, I noticed a little more dirt in the bottom of the tank. Not sure where this dirt is coming from. Is it possible there is a leak in one of my pipes and dirt is entering the cracked pipe? Any comments would be appreciated.

Could be iron sediment, does the dirt have a red tint to it.. are you on well water or city? A hole not likely . But if you have had a recent outdoor pipe repair , some dirt can get in you pipes during repair, but you would have dirt in your faucet aerators as well.. take a close look at the sediment in the tank see what color it is..

Will do, I have noticed a reddish tint developing on the tank's inner walls, but of the three bathrooms in my house this is the only one with a reddish tint on the inner tank walls. BTW---this bathroom is the least used of all the bathrooms---maybe 2 times a week at max. If this is do to iron why would the sand come back after I completely drained the tank and removed all sediment? Thanks.