To find the capacity of the tank, we can set up the equation based on the information given:
If \( 221 \) liters of water is \( \frac{1}{6} \) of the total capacity \( C \) of the tank, we can write:
\[ \frac{1}{6}C = 221 \]
To find \( C \), we can multiply both sides of the equation by \( 6 \):
\[ C = 221 \times 6 \]
Calculating that:
\[ C = 1326 \]
So, the capacity of the tank is \( 1326 \) liters.