Clearwater Tech CNT-30 30gal 1.25 In/Out Contact Tank will maximize the effectiveness of ozone, once it is thoroughly mixed and have adequate time to react with the contaminants in the water before returning to usage or further processing. ClearWater Tech contact vessels are designed to achieve maximum ozone contact efficiency. All tanks are approved by NSF International and come in a variety of sizes from 30 to 850 gallons depending on the application.