As water travels through objects including pipes, valves, and angle points, or goes up hill, there are losses due to the friction. These losses are called “friction” or head loss. There are published tables listing head loss factors (also termed C factor) for pipes of differing age and material, different types of valves and angle points, etc. However, in this text, we will focus on the theory more than the actual values.
If water is traveling through 10,000 feet of pipe that has head loss of 3 feet, passes through 4 valves that have head loss of 1 foot for each valve, and passes through 2 angle points that have head loss of 0.5 feet each, calculate the total head loss.
- Answer: 3 feet + 1 foot + 1 foot + 1 foot + 1 foot + 0.5 feet + 0.5 feet = 8 feet
Summing all of the head loss values yields the answer.
In distribution systems, water is pumped from lower elevations to higher elevations in order to supply customers with water in different areas termed zones. Water is also pumped out of the ground through groundwater wells and from treatment plants throughout the distribution system. As water makes its way through the distribution system head loss is realized (as mentioned in the previous paragraph) and pumps must also overcome the head loss from the elevation changes.
The diagrams below help illustrate the differences between suction lift and suction head. Suction lift requires more work by the pump to move the water from point A to point B. Suction head provides some help (head pressure) to get water from point A to point B.
Suction Lift and Suction Head
Solve the following problems.
A well pumps directly to a 25-foot tall water tank that sits 200 feet above the elevation of the well. If the total head loss in the piping up to the tank is 5 feet, what is the total pressure in psi on the discharge side of the well?
A booster pump receives water from a tank that is 40 feet above the pump and discharges to a tank that is 275 feet above the pump. What is the total head (TH)?
A well located at 750 feet above sea level has a below ground surface water depth of 38 ft and pumps to a water tank at an elevation of 1,030 ft above sea level. The water main from the well to the tank has a total head loss of 11 psi. What is the TH in feet?
A housing tract is located at an approximate average elevation of 2,225 ft above sea level and is served from a storage tank that is at 2,330 ft. The average head loss from the tank to the housing tract is 15.5 psi. What is the minimum water level in the tank to maintain a minimum pressure 40 psi?
A water utility has two different pressure zones (1 and 2.) The zone 1 Tank is 30 ft tall and sits at an elevation of 850 ft and the zone 2 Tank is 40 feet tall and sits at 1,061 ft. The booster pump from zone 1 to 2 sits at an elevation of 925 ft. The head loss is 19 psi. Tank 1 is half full and Tank 2 needs to be ¾ full. What is the TH?