Pool Time Calcium Hardness Increaser works to prevent pool surface damage and corrosion of pool equipment by raising calcium hardness. When total hardness levels are too low due to low calcium levels, pool equipment and surface are prone to corrosion and etching. Broadcast calcium hardness increaser to the deepest end of the pool to help maintain ideal total hardness levels of 175 to 225 parts per million. TERMS OF SALE: If, after receiving this item you discover that it was not the one you wanted, simply return it for a full refund within 30 days. Refund is void if you have installed, used or damaged the item in any way. Item must be returned with its original box, packing materials and instructions. International buyers: Customs fees, duties, taxes, tariffs other fees are your respons.