Sufficient water supply is one of the most important variables in the application of good-quality dry-mix shotcrete. It is often overlooked, especially by people who are new to the industry. Although the flow required is relatively minimal (10 to 60 L/min [2.5 to 16 gal./min]), all too often the water pressure requirements are not given the attention they deserve. It is important for the water pressure to be at least 100 kPa (15 psi) greater than the pressure in your conveyance hose. Conveyance hose pressure will vary based on many factors such as length and inside diameter, material gradation, vertical ascents, rpm of the rotor or bowl, and the adjustment of the valves feeding the compressed air to the conveyance hose. Hose pressure will usually vary from as little as 200 kPa (30 psi) to as great as 480 kPa (70 psi). It is best not to rely on an onsite water source. A good-quality water tank and pressure booster pump will easily pay for themselves in the long run.