For many jobs requiring single pours of less than 50 cubic yards, contractors can profitably use small-line pumps. The smaller pumps are also a practical alternative for larger pours with slow placing rates. WHAT IS A SMALL-LINE PUMP? Small-line pumps can be divided into two general categories--pea-rock and 1-inch-minus pumps. Pea-rock pumps are trailer-mounted ball-valve machines designed to pump plaster, grout, or concrete that usually contains about 70% sand and 30% 1/2-inch-minus coarse aggregate. Trailer-mounted or truck-mounted 1-inch-minus pumps (also called 3/4-inch rock pumps) usually have a swing tube, S-tube, or rock valve instead of a ball valve. The 1-inch-minus pumps have features similar to larger trailer pumps and are designed to pump structural concrete for floors on ground, elevated decks, columns, and other structural members. WHY USE A SMALL-LINE PUMP? Pea-rock pumps are ideally suited for residential applications. They're small enough to be towed by a pickup truck and used without blocking or overloading streets. For commercial work, 1-inch-minus pumps are often the most practical machines to use when the pour rate is determined by how fast the concrete can be placed or finished. GETTING THE MOST OUT OF YOUR PUMP INVESTMENT Contractors who buy their pumps also need to invest in operator training and a regular maintenance program. Concrete pumps require more frequent inspections and service than most types of construction equipment.