The increase in pH can be calculated by subtracting the initial pH from the final pH.

$$ \text{Increase in pH} = \text{Final pH} - \text{Initial pH} $$

In this case, the initial pH is 1 and the final pH is 3.

$$ \text{Increase in pH} = 3 - 1 = 2 $$

Therefore, the increase in pH is 2.