Why is it so important not to flush the toilet after every trip to the toilet to urinate?

Fresh urine from a healthy person is mostly water along with urea, salts, and other waste products.

However, after sitting for a while, bacteria can begin breaking down urea and producing ammonia-like odors.

 

That means the main practical problems are usually:

* Smell
* Staining
* Mineral buildup
* Appearance

Regular cleaning is still important.