We were consulted to offer our opinion in two cases where traditional ‘tile & grout’ type waterproofing failed miserably. The purpose of using these structures to store water was not served.We suggested to line the entire area using Polygomma EPDM liner. The EPDM liners are durable, UV resistant and works well for decades even when water is always ponded on it, and in all weather conditions.EPDM liners/membranes should be the first choice for a long term waterproofing of structures.