Ideal for line pumps. *Volume Discounts Available* US Patent Number: 8,113,220 B2: The Original Concrete Washout Bag. Envirosac Medium Waterproof Hybrid Bag Lined (43""W x 43""L x 19""H). This concrete washout bag works with washout for pump trucks as well as ready mix trucks. 40% stronger than other brands; the bag has a waterproof liner and holds .8 cubic yards.