Supply of Water

HSN Code : - 2201. GST Rate 12 %

If drinking water packed in 20 Ltr bottle then GST rate is 12%.

In your case Mr. A supply through own tanker and its more than 20 ltr department may ask for GST.

Another view is possible that in GST written 20 Ltr bottle but its not bottle its tanker so no GST applicable.

But in my view you should go for GST Registration.

Rectify me if I am wrong.