The best thing to do is wait about 8 to 10 minutes
if the stains are really bad.
The other thing you can do is take the lid of the
top of the tank and unhock the chain so the bobber
doesn't let the water go through when you flush
the toiliet. I would put straight vinegar in the
bowl with hot water fill to the brim for a while
this will loosen the hard water. May need to
do this a few times, if it is really bad.
Please note you will need to pail out alot
of the water and then put the chain back on
and flush. You need to purchase a bristle
style toilet brush and clean your toilet bowl
more frequently.