Why is it called jockey pump?

On a fire protection system requiring a fire pump, there is a small pump that maintains pressure above the pressure settings of the larger fire pump. Hence the name “jockey pump.” The purpose of a jockey pump is to maintain pressure in a fire protection piping system so the larger fire pump does not need to run. A jockey pump package consists of a pump, motor and controller.

Two Types of Pumps

There are two types of pumps available for jockey pump applications. The preferable design is a centrifugal pump. The other type is a positive displacement regenerative turbine pump. A turbine pump appears to be the perfect choice as a jockey pump because it can generate high pressures at low flow rates with low horsepower. This is exactly what we are looking for in a jockey pump. However, a turbine pump operates on very close tolerances. If those tolerances wear out a few thousandths of an inch, the ability to generate enough pressure is lost.

Of greater concern is the ability of a positive displacement regenerative turbine pump to generate very high pressure if left running. This pump has the ability to exceed rated system pressures and burst pipes. The solution to this problem that works on paper is to install a pressure relief valve on the discharge pipe of the jockey pump. The thought behind this is that the valve will open at a preset level and dump excess pressure down the drain before it can cause damage to the sprinkler system. However, the reality is that most pressure relief valves are regulated by a spring that is exposed to the water in the system. The valves need regular exercise to keep them from becoming stuck closed. The relief valve on a jockey pump will never operate until the dangerous over-pressure condition occurs. Then the relief valve will most likely not open or open such a small amount that over-pressurization will still occur. A centrifugal pump is not dependent on tight tolerances and will merely churn at the highest pressure point on the curve.

Examples of centrifugal jockey pumps.