How much crack will 20# fill, or, what is the volume of the tub??

A 20 lb pail of QUIKRETE® Hydraulic Water-Stop Cement yields approximately 0.168 cubic feet when placed. Yields will vary based upon waste, water content, etc. QUIKRETE® Hydraulic Water-Stop Cement is not meant for applications to flat surfaces, and cannot be used for resurfacing or coating a surface or large repairs. A golf ball size mix is appropriate for most applications. If more than one application is needed to complete the repair, each application must be made before the prior application has set completely. When making repairs, getting a good color match can be difficult - we always recommend trialing a small quantity of the repair material in a discrete area, and allowing it to cure for one week to determine whether the color and overall appearance are acceptable before using the material in less discrete areas.