It is imperative you do research and answer key questions when selecting a pump.
By Ron Peterson
When deciding which pump to use or how to use it, there are several factors to consider.
Where will it be used? In a water well? If so, a deep or shallow well? Surface or submersible? Or is it for slurry, sludge, mining, manufacturing, or processing?
These are just a few of the many applications for pumps and each one has its own subset. We will focus exclusively on water well applications for this column.
Considering Your Options
Let’s consider water transfer. Pumps are typically rated brand new, at sea level, and with a 12-foot positive head. However, very seldom are these parameters encountered in reality, so what do we do?
In planning your well, make sure you or your consultants have carefully researched all of the available well offset records to minimize the possibility of drilling a dry hole and to ensure you have the potential of a well in the desired location. This will improve your chances of having a water supply that satisfies your needs.
Here now are some of the common types of hand or manual pumps used in the water well industry.
Pitcher Pump: Designed for shallow water well applications less than 25 feet, a pitcher pump requires manual, repetitive pumping to lift water from the ground. It is usually made from cast iron and includes an adjustable cap and handle. This type of hand pump is especially useful during power outages when automatic pumps can’t operate.
Piston Pump: For wells over 25 feet deep, specialists install a more powerful pump that can displace water upward from considerable depths. Piston pumps use a piston sealed within a cylinder and rods that drive down deep into the ground.
Suction Pump: Suction pumps are used on farms and homesteads. They have a maximum lift-height of up to 7 meters. The pump cylinder and valves are above ground in the pump head. Repeated pumping is required to suck water up the riser main, into the cylinder, and out the spout.
Lift Pump: Commonly found in developing areas, lift pumps can raise water to a height of up to 60 meters. The pump cylinders are installed below the ground and work by elevating a column of water upward. Lift pumps require minimal effort to operate.
Treadle Pump: This type of hand pump works through the contraction and expansion of a diaphragm in a closed system. To draw water upward from the well, a user needs to pedal with their feet or hands. A drawback to treadle pumps is the relatively high price of replacement diaphragms.
Besides these types of pumps, another option is a windmill. Windmills convert the rotary motion from the windmill to an up-and-down pumping motion similar to a hand pump, using a plunger and valving to lift water out of the well.
However, while interesting, surface pumps have limited abilities especially when it comes to lifting water and in how far they can pump water to deliver it.
Making the Right Selection
Surface pumps are normally not the best choice for use on a water well. So, let’s look at the application and some real-life encounters and use the information to design a well and pumping system.
Remember, pumps are generally designed to pump or push water and not to suck or pull it from its source. They have limited suction; otherwise, they would probably be called sucks.
In a water well with any depth at all, the typical pumps used are submersible and line drive turbines. Submersible and vertical turbine shaft pumps are better suited for use in a water well.
So, what information do we need to properly select the pump? Two immediate questions to ask are: What is the maximum flow that we need? What can the well reliably produce?
Others are: What is the static water level? What is the anticipated measured drawdown or lowest point in the cone of depression?
Knowing this information can help us determine what pump to use and where to effectively place the pump. If the pump is set above the cone of depression, there is a good chance it will draw air, which will make it impossible to have a predictable flow and cause premature failure of the pump.
To properly size a pump, you need to know:
- The total suction or the lift out of the well in feet
- The difference, or the total lift in feet to the point of discharge
- The total friction loss due to resistance to flow in the pipe and distance to be pumped
- The total required delivery pressure in feet (psi × 2.31).
We also need to know how the pump will be driven (i.e., type of power: electric, gas, or diesel). If electrical, what type of power service is available (115/230-volt single phase, 230-volt three phase, or 460-volt three phase). And remember, electrical can also be solar power.
Where will the control be placed? Inside or outside?
What kind of a control will you use: VFD, across the line, or soft start?
Once you have gathered all the necessary information, you can decide what pump will provide you with the most efficient, predictable water supply at the lowest overall cost. When deciding which pump will best fit your needs, use all available resources, including your local pump supplier and technical resources from the pump manufacturer.
Wrapping Things Up
I frequently say that a man must know his limitations. It is my belief that we borrow the earth’s water and other resources from our descendants. Therefore, we need to do everything that we can to leave things in better shape than when we found them.
That is why it is important we answer the questions I have presented and build the best water systems we can for our customers.
Let’s work together, so we make the industry stronger and better able to meet the needs of everyone involved.
Ronald B. Peterson has been involved with the drilling industry for more than 40 years. He previously worked for Baroid Industrial Drilling Products and is now with Mountainland Supply Co., a supply company in Orem, Utah. He served as The Groundwater Foundation’s McEllhiney Lecturer in 2015 and was given NGWA’s most prestigious award, the 2013 Ross L. Oliver Award. He can be reached at firstname.lastname@example.org.