How can we suggest the dosge of sulphuric acid in cooling tower water?

i have problem to suggest the dosage of sulphuroic acid in cooling tower water to decrease the pH of cooling water during the water treatment of cooling tower , in cooling tower due to evaporation the pH of cooling water go to the high side and its necessery to bring the pH of cooling water to the dowm side in range of 6.5 to 8.3 thanks