water stands in the bowl, why not?
toilets are not by themselves designed to hold water unless
a vented loop is installed in the discharge line with the top
of the loop generally 4 inches higher than the top of the bowl. The higher the loop the more water will remain after each flush.
See the specific toilets installation manual for specifications
and loop height limitations.
Vented loops may need to be installed higher for safety
reasons (see installation manual for further details)