pH + pOH = ?

pH = -log₁₀[H ⁺ ]

pOH = -log₁₀[OH^-]

Since the distilled water is neutral,

[H ⁺ ] = [OH^-] = 10^-7

[H ⁺ ] × [OH^-] = 10^-7 × 10^-7

[H ⁺ ] × [OH^-] = 10^-14

Taking negative logarithm on both sides,

-log₁₀[H ⁺ - log₁₀[OH^-] = -log₁₀[10^-14]

pH + pOH = 14