The 31-Series is our continuous-duty on-demand positive displacement pump. It provides reliable performance in moderate water flow, high-pressure applications. This 3-chamber diaphragm pump provides up to 1.8 gallons per minute and is capable of self-priming up to 6 vertical feet, and can run dry without damage. This automatic demand water system pump has a built-in pressure switch, which automatically starts and stops when the fixture is opened and closed. They are easy to install, service and winterize.