ForConstructionPros.com

Pumps are a common item in many rental inventories. In a lot of cases, renting them to customers is a simple matter of determining the right type of pump and the correct size. When your customer has a large or complex project, however, it's helpful to understand a little about hydraulic science.

The start to any successful pump rental begins with asking your customer what they are trying to do, says Pete Snow, training manager at Godwin Pumps of America. "Getting a big picture view of the pumping application helps determine the follow-up questions and, ultimately, the design of the portable pumping system. Is it a small dewatering job at a construction site for a few hours or days, or is it a large sewer bypass requiring continuous pumping for weeks? The level of complexity dictates the course of action."

Bill Thompson, president of Thompson Pump & Manufacturing, notes some of the questions that the rental counter person should ask initially:

• Where is the application/pumping taking place?
• What are you pumping?
• How much needs to be pumped?
• How high does the liquid need to be pumped up/how much does the liquid need to be lifted/is the liquid in a large ditch (in other words, what is the lift pressure)?
• How long will you be pumping?

According to Snow, small dewatering jobs can be handled by gasoline-powered wet-priming pumps with suction and discharge sizes of 2 to 3 in. in diameter. These pumps can run for several hours on a tank of gas and will move up to 250 gallons per minute. "The system design usually includes 20 to 30 feet of suction hose and 100 to 200 feet of layflat discharge hose," Snow says. "General rental businesses can meet these application requirements."

On the other hand, large dewatering or sewer bypass jobs are far more complex and can involve 24-hour pumping operation and flows up to 4,000 gallons per minute and more.