Frequency of cleaning the borewell for silt

The borewell is stinking, what should be the frequency of cleaning the borewell?


We cleaned our borewell in 2016 for silt deposition problems due to which we got a rotten stinking smell in tap waters. I would like to know what is the exact frequency of cleaning borewell for a silt problem? I am again getting rotten smell in my borewell now. Previously it was cleaned in 2016. It's a 300 feet borewell.

Thanking you