Jagjeet, I don't know how often to clean the water tank in India, but I can offer a suggestion based on my experience. According to the code of fire prevention in China, our contractor must conduct a thorough inspection and testing of the fire facilities around our plant annually. This includes the sprinkler system, alarms, fire extinguishers, outdoor hydrant system, and of course, the water storage tank as you mentioned. We coordinate with the local fire department to protect the property during the tank drainage. The contractor enters the tank to clean it under the Confined Space Program. If you are a customer of FM Global Insurance, you must comply with the Red Tag Permit from the local FM company.
Best regards,
Michael Zhang