: afetr 3 years of usage i have noticed that after a flush my toilet bowl does not fill up to the desired level(there is very low level of water remaining in the bowl after a flush) this makes it harder the keep the toilet clean. what could be the problem and how to fix it?

Arek,
Check the overflow "fill tube". If the small black tube is not putting water in the overflow, then the bowl will not fill all the way.
Most toilets are this way.
The overflow is the white plastic tube that sets with the flapper.