Prepare to Get Pumped Up

In the event of a flood, have the right pump on hand to handle what could be in the water.

• By Pam Meyer
• May 01, 2011

Professionals tasked with administering safe practices in the workplace always must be thinking ahead. Being prepared is crucial in several aspects of the job, including disaster management. While the spring season may bring warmer weather and sunny skies, it's also notorious in several areas of the country for bringing heavy rainfall and the possibility of flooding.

Small de-watering pumps are ideal for moving water if excess rainfall or a full-blown flood is threatening the workplace, whether it be an indoor office or an outdoor job site. Pumps come in a variety of options, from the smallest centrifugal models to the largest trash units. Because some models are designed to move muddy, thick water, while others are capable only of handling clear water, safety professionals need to know which pump is suited for what type of water to be sure the proper pump is selected for the situation.

Choosing an incorrect pump can result in damage to the pump's components, not to mention poor performance -- and when the water is coming, who has time to wait for a pump that is not working properly? Pumps should be selected based on the type of water being moved. But what makes a certain type of water acceptable for one pump but not for another? To make an accurate choice of the best pump for the job, you must look below the surface and investigate what is, or could be, in the water.

The Clear Choice
For applications where clean water must be moved, centrifugal pumps offer the best and most inexpensive means to do so.

Centrifugal pumps have narrow impeller vanes, making clear water that is virtually free of debris the only type of water these pumps are able to handle. Obviously, there is always a chance that seemingly clear water will contain at least a small amount of debris. This is why these pumps are equipped with a strainer, which acts as a safety net and stops unforeseen debris from entering the intake hose. Moving rainwater from indoor office buildings is an example of where this pump would do a fine job.

It's pretty basic what types of liquid a centrifugal pump can handle. But what if the water is even slightly muddy, sandy, or littered with debris? The strainer will help prevent unexpected particles from damaging the pump, but if any amount of debris is detected in the water, be aware that another type of pump exists specifically for this type of situation. For water that may contain debris that could clog or damage a centrifugal pump, a semi-trash pump would be the best option.

When Centrifugal Won't Pump It
In the simplest terms, semi-trash pumps work in the same way as centrifugal pumps but have thicker impeller vanes and a larger volute discharge opening. Small debris up to ¾ of an inch, or about the size of a dime, can flow through without any problem.

A semi-trash pump should be used in any situation where there is uncertainty that a centrifugal pump will be able to handle the job. Water that appears a bit dirty or sandy should be moved using this type of pump. If there is even a hint of debris, err on the side of caution and go with a semi-trash pump -- especially true for outdoor areas where even small particles of dirt may be mixed in with the water.

While a semi-trash pump is capable of handling more than a centrifugal pump, it can still have problems if the debris is too large. It is also incapable of handling sticks, stones, or concrete particles. If a user detects any of those types of debris in the water, he should opt for the next level of pump: a trash pump.

Sticks and Stones Won't Break These Bones
For items that are too big for a semi-trash pump to handle, a trash pump would be the best choice. With even thicker vanes than a semi-trash pump and the same large volute discharge opening, a trash pump operates the same way but allows larger debris to flow through. Small sticks, stones, and other debris from ¾ of an inch to 1 ¼ inches, or up to the size of a half dollar coin, can successfully go through a trash pump. This makes it ideal to handle thicker, sandier, and dirtier water than a semi-trash pump.

These pumps are a good choice for situations where high volumes of water that may contain trash need to be moved, especially if there is uncertainty whether the debris would be too large to be handled by a semi-trash pump. Removing excess water from outdoor sites, such as road repair and large construction areas, is an example of an application that may require a trash pump. Bits of broken concrete and other debris of similar size are more likely to be present on these sites, and a trash pump will be able to keep the water moving even with these items lurking beneath the surface.

A trash pump can definitely handle thicker water and fairly large debris. But what about really muddy or viscous water that may contain larger solids, trash, or other particles or water that is so thick, it is almost impossible to detect what kinds of debris may be submerged? For the toughest water with large debris, a diaphragm pump will handle it best.

Diagnosis for Diaphragm
Often referred to as "mud hogs" or "mud pumps," diaphragm pumps are the ones to choose when the water is so thick or dirty that the user cannot detect what may be lurking underneath the surface.

Diaphragm pumps are capable of handling sticks, stones, mud, trash, and other debris up to 2 inches, or a bit larger than the size of a golf ball. Basically, anything that can fit through the opening will be able to go through. It will pump re-circulated water and muddy, sandy, and viscous water.

All these capabilities mean a higher price tag for this type of pump. For this reason, a diaphragm pump typically is used only when it is the sole machine that can handle the job. And it operates at a slower rate than the others, so be prepared for the job to take a bit longer if using this type of pump. For instance, a 3-inch trash pump will move water at a rate of about 315 GPM, while with a 3-inch diaphragm pump only moves water at a rate of about 60-70 GPM.

Other Considerations
By now, you should be ready to choose a pump based on the type of liquid being moved. But before setting foot in any store, there are a few more factors to consider.

While the type of water may be the most important influence on the decision, other factors must be considered when choosing a pump. For example, pump sizes are based on how much water per minute the pump will move, and the bigger the pump, the faster it will move the water. In some cases, a smaller pump would be sufficient to get the job done, but a larger pump may be chosen to get it done faster. For a scenario where water damage would be a major and expensive threat, such as in an office building, time is precious and a larger, fast pump would be imperative. And remember, diaphragm pumps move the largest debris and dirtiest water but work slower than the other types of pumps.

Furthermore, be sure to compare the quality between pumps. It may be tempting to save money and skimp on features, but a higher-quality pump that withstands time and abuse will pay for itself in the long run and provide reliable peace of mind the next time rain is in the weather forecast.

Because the engine is the driving force behind the pump, it is important for it to be of high quality and long lasting. Additionally, the pump housing, impeller, and volute are essential to superior operation, so be sure they are well made and not plastic. Some manufacturers equip trash pumps with a wear plate that absorbs the impact of sticks, stones, and other large debris before they enter the impeller. This is a valuable feature that can ensure a longer life for the pump while reducing maintenance requirements. Finally, lower-quality pumps often don't have frames. Choose a pump with a quality frame to protect the pump, engine, and all components.

Check the maintenance requirements of each pump. Regardless of the pump's quality and how well it is suited for the job, a pump that is not properly maintained will likely cause frustrating delays and result in the need for expensive repairs -- not to mention the potential cost of water damage. Select a pump that is easy to maintain and requires only minimal professional attention, and be sure to follow through with maintenance to help prolong the pump's life.

With so many pumps available, it can be difficult to choose the correct one. Improper selection may result in unsatisfactory performance of the pump, which could lead to bigger problems in emergency situations. Having knowledge of each type of pump and, more importantly, what could be in the water being pumped, will ensure the best selection is made for each scenario.