This article will emphasize those factors of pumping equipment that most significantly affect pumping of lightweight concrete. Some pumps are capable of handling harsh, low-slump mixes for horizontal distances of 500 to 1000 feet, but others do not have enough horse power or piston head pressure to handle mixes that are hard to pump. Concrete pumps are too often sold without adequate understanding of their actual capabilities in all circumstances. As a result, pumps are sometimes assigned to projects for which they are underpowered. In other instances pumps are inadequate because they need maintenance or engine repair. It takes a larger line to pump concrete with larger aggregate. While the ACI 304 report, "Placing Concrete by Pumping Methods," recommends that the maximum size of aggregate be no more than one-third the inside diameter of the delivery system, it is safer to use a line in which the aggregate will be no more than one-fourth the diameter. However, to have any hope of pumping, the pump and the lines must be adequately lubricated with grout. About one-half cubic yard of grout will lubricate about 1000 feet of line. This grout should be introduced just ahead of the pumping mix.