How to Select the Right Pump

Factors to Consider When Selecting a Pump

Every construction project requires that you go through the same list of considerations to determine which pump type is the right one for each site. It is very rare that a site will not require a pump, especially since the longer a project takes to complete, the more likely you will encounter some water issues. Plan to have pumps available to remove water and other liquids that could accumulate on site. Whether you need to dewater the jobsite before you begin, or at some point over the course of the job, having the right pump for the full construction project can save you money and time. 

Every new construction job is going to require you to take some time to assess the site, the terrain, the types and amounts of liquid, and the distance that you’ll need to move the liquid. While this will take a good bit of time before you can get started on the job, you can create an easy checklist to help you quickly assess each situation to determine what will work best.

 

Evaluate Each Site

The first – and typically easiest – consideration is the site itself. This will help you to significantly narrow your options since the different types of pumps are often made to operate best at certain jobsites. Consider the following factors:

• The vertical distance between the liquid’s surface to the highest discharge hose
  
  
• How long the pipe or hose needs to be and what kind of material it should be made of
  
  
• If you need a sprinkler or nozzle
  
  
• The likely discharge volume
  
  
• If the project is in a higher elevation (this can reduce the pump’s performance)

Consider the Liquids and Materials to Be Pumped

Along with your determination on removing liquid, it’s important to consider what other materials will likely pass through the pump. Clear water will move through a pump a lot differently than dirty water or water that is mixed with chemicals. If you will be moving mostly clean water, a general-purpose pump is more than enough. You may need a trash pump, however, if the liquid contains a higher amount of solid content. If the water is likely to have chemicals in it, multi-purpose pumps are designed to handle a wide range of chemicals so that other areas aren’t contaminated.

For water that is likely to be deeper, submersible pumps can be fully covered by water and still be able to have optimal performance.

Determine the Required Pump Capacity

Check the manufacturer’s information to see what the pump’s capacity is. This will let you know how much fluid a particular pump can remove per minute or hour. For larger liquid pools, you will likely want a pump that has the capacity measured in hours (GPH). Locate the pump as close to the liquid as is practical for best pump performance. You want the suction head to be as small as possible to reduce the formation of bubbles in the pipe or hose.

Since the water will likely want to run back to the original resting place, you will want to make sure that the pump moves the water further from the site. The force used to move water is measured in psi.

The piping material is also important to consider as the longer you need to have the pump on site, the more durable you need the pipes to be. All liquid causes friction when passing through hoses and pipes. When passing through steel, water creates more friction than when it passes through vinyl or PVC. The longer the hose, the more friction gets built up in the piping. With the increase of friction, the water flow slows, which in turn decreases your pump’s discharge capacity.

 

Precautions When Dewatering Your Jobsite

Every jobsite needs a solid dewatering plan to avoid on-site erosion. It’s also important to make sure you are in compliance with state and federal regulations and have all your permits in order. Environmental Protection Agency regulations require construction and stormwater discharges to comply with a National Pollutant Discharge Elimination System permit. You may be able to discharge water to a nearby catch basin or body of water. Always adhere to best water management practices when dewatering to lakes, wetlands, or sewer inlets. If you need to filter out sediment from the water, you’ll want to use geotextile fabric dewatering bags. Size your dewatering bags based on pump flow rate and the size and type of sediment you’re removing.

Keep these things in mind when making your site dewatering plan:

• Do not pump water directly into slopes
  
  
• Direct water flow into wooded areas if possible, to minimize erosion
  
  
• If any areas are showing signs of erosion or becoming unstable, discontinue dewatering immediately
  
  
• Any channels used for dewatering must be stable, and preferably lined with vegetation
  
  
• Avoid dewatering during heavy rainfall
  
  
• Do not directly discharge water contaminated with oil, grease, or other chemicals without first using an oil/water separator

Study the water table conditions in the area and refer to the geotechnical and groundwater site investigations to assess any potential risks. If needed, bring in an engineer that specializes in soil stabilization and groundwater control, or consult with your White Cap product specialist.

Estimate How Long You Will Need to Use the Pump

One obvious factor that can be tricky is determining how long you will likely need the pump. You want something that will be highly efficient and reliable for as long as you need it, but for longer projects, this can be incredibly difficult to predict.

Spend time reviewing the pump specifications and compare it to the project requirements. Based on your estimate for how long the project will take to complete, you should be able to determine how long you will probably need the pump.

However, not all jobs will need to have a pump on site for the entire construction project. If you only need to remove water from one location and are sure that water will not remain a problem, you’ll need to determine how long each of the pumps will take to dewater the surface or groundwater. If the construction project will take weeks or longer, you will need to consider having a pump that will continue to dewater the area as precipitation and seepage could cause erosion resulting in more water issues.

This could mean having two different pumps on the jobsite: one to dewater a larger volume, then a second to keep the area as dry as possible.

Don’t forget to assess your own experience with pumps on previous projects; there’s nothing like practical experience to help you make the right determination.

Noise Constraints Are a Factor

Verify that the project or location where the project will be completed doesn’t have any noise restrictions. Residential areas tend to have requirements about how much noise can be made – especially at night. If so, that will help to narrow which pumps you can use.

Review the Total Head

The term “total head” refers to the pump’s pressure differentials as it works, and it is calculated by adding the dynamic suction head and dynamic discharge head. Most pump manufacturers will make it easy to determine the total head of each pump by providing a chart that illustrates the curve to find the optimal use. This will simplify your assessment but be aware that the performance curve could exclude the frictional losses. If this is not included in the manufacturer’s performance curve, the system will probably not meet your expectations.

Always check the pump specifications to see what the frictional losses are, as well as any other details you want to consider about the performance before you make your decision. The following are the primary performance considerations:

• The elevation of the pump versus the elevation of the water surface
  
  
• The elevation of the pump versus the elevation of the discharge head
  
  
• The pump’s discharge capacity

The total head can be calculated by adding the discharge and suction, then you can estimate the discharge capacity when you check the performance curve.

Account for the Engine Performance and Elevation

You want a pump with the best possible performance for each project so that it will quickly move as much water as possible. Since the pump’s performance is affected by the elevation, the greater the elevation, the lower the engine’s performance. Higher elevations have less air, which reduces the combustion. For every 1,000-ft increase in elevation, you can expect the maximum engine power to be reduced by about 3.5%. It can also reduce the pump’s discharge capacity and available suction head.

Consider the Best Power Source for the Site

Another consideration (but not the least important) is the power source that you will use for the pump: combustion or electric. This could be an easy decision if you don’t have a power source readily available. If you have a generator onsite, you will need to ensure you have the right plugs for the pump. If you do have an electrical source on site, you will need to make sure that the cables are long enough for the pump to be optimally situated near the water. For example, submersible pumps often run on electric power, so they require a generator for the best results.

Pumps that require fuel may run on gas, diesel, or hydraulic. There are even pumps that can be operated manually, but it is rare that these will be necessary on a jobsite.