Prevent Water Woes

Since water covers nearly 80% of the earth's surface, chances are good that at some point you'll run into enough of it on a jobsite that you'll need to get rid of it.

"Sometimes we find water in places where we'd rather not have it," says Radu Murgescu, construction and mining market manager at ITT Flygt Corp. Basements are one place; excavation sites are another. At times, water can be your worst nightmare. "This is where pumps come in."

A selection of pump types

Contractors have a variety of pumps from which to choose. Some of the most common types used on construction sites include trash pumps, diaphragm pumps and submersible pumps.

One of the most versatile of the group is the trash pump, especially one that is trailer-mounted, says Jeff Cooper, district manager, Pump & Power, United Rentals, Inc. "This type of pump is easy for contractors to move around and relocate where needed," he says. "Plus, most models will allow some degree of solids to pass through the pump. So these pumps also allow contractors to pump a variety of densities ranging from clean water to sludge."

These types of pumps typically have high suction lifts and relatively high discharge heads, as well as a simple design with few parts. However, they are not a good choice for pumping thick mud. And when there is only a small quantity of water to pump, priming will be lost.

Trash pumps are available in either wet priming or dry priming versions, explains Joe Belli, product marketing specialist with Thompson Pump & Mfg. Wet priming pumps require that the casing be filled with water before operation. Dry priming pumps utilize an external priming system, usually a compressor or a vacuum pump, to assist in purging air from the suction line of the pump system.

This allows the pump to achieve prime without filling the casing with water before operation. This maintains prime by assuring that an unknown influx of air will not reach the pump casing, causing cavitation and affecting the pump performance.

When water begins to thicken with dirt and debris, you may want to consider a diaphragm pump, which is designed to handle muddy water, sludge or any liquid with a high percentage of solids.

"One of the best features of the diaphragm pump is that it can run dry indefinitely without damage," says Belli. "These pumps are ideally suited for the construction industry, as well as for municipal and industrial applications where dry priming pumps are required."

Diaphragm pumps handle slow seepage or full capacity with each stroke. These pumps also keep jobsites dry when there is a small inflow. Another plus is that the diaphragm and valves are typically easily replaced.

Drawbacks include less capacity than a self-priming centrifugal pump for the same investment, and limited to low discharge pressure.

Submersible pumps provide instant priming and are capable of moving large amounts of water with high discharge heads. They're a good choice when you need to pump fluids that are a considerable vertical distance from the discharge area, such as in sewers, pits and mines.

They're also relatively low-maintenance machines that can even run dry. They do not require constant attention and you don't need to worry about flooding or freezing conditions. However, they are not designed to pump thick mud.

Another type of pump that is gaining in popularity is the well point pump. Initially developed for areas with high ground water tables, such as Florida, these pumps are now being used in states as far away as Rhode Island and Michigan. "Regionally speaking, the well point pump is the most commonly used pump for ground water dewatering tasks in Florida," says Belli. "These are typically used before excavation begins to remove any underground water. This makes the jobsite dry to allow for excavation or any other underground work to begin."

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