Pump Preservation

May 1, 2001
Whoever quoted the phrase ignorance is bliss has obviously never tried to repair a portable pump. While pumps generally have few working parts, knowledge

Whoever quoted the phrase “ignorance is bliss” has obviously never tried to repair a portable pump. While pumps generally have few working parts, knowledge is the key to a pump's long life.

The most common cause of pump performance problems is operator misuse. The first step is to understand the different kinds of pumps available and their specific capabilities and limitations.

There are several kinds of self-priming portable pumps. A self-priming pump will clear its passages of air if it becomes air bound — meaning it can no longer form a vacuum to pull water into the pump — and then resume delivery without outside attention. The self-priming feature permits the pump to continue to run even when the minimum pumping capacity is greater than the seepage of water.

Portable pumps feature discharge sizes ranging from 1.5 inches to 4 inches and are powered by either a 2- or 4-cycle gasoline air-cooled engine or an electric motor.

Picking the right pump

The two most popular kinds of self-priming pumps are centrifugal and diaphragm.

The agricultural pump and the trash pump both fall into the category of the centrifugal pump. The agricultural pump transfers clear liquids and dewaters and is popular for turf irrigation and small farming operations. The trash pump transfers water mixed with large amounts of spherical solids. Most trash pumps can tolerate solids up to one half the size of the hose diameter, which make them useful on construction sites, excavations, drainage ditches and for septic systems.

Centrifugal pumps use an impeller mounted in housing called a volute. The engine shaft rotates the impeller at high speeds and creates a vacuum at the center, which in turn pushes water up the hose to the pump. The rotating impeller forces water against the internal surface of the volute, which then directs the water to the discharge outlet.

These pumps have a high suction lift that eliminates the need for placing the pump directly at the water source. Centrifugal pumps are designed for water containing up to 10 percent suspended solids by volume and will pass solids up to one-fourth of the hose diameter.

The diaphragm pump is also a self-priming pump. But, instead of an impeller, it uses a heavy elastomer plate of rubber called a diaphragm to form a sealed water chamber. As the diaphragm moves up and down, vacuum and pressure move the water through the pump.

Designed for transfer of water with high abrasive solids, such as mud, sand, silt and sludge, this type of pump is usually used for industrial maintenance and municipality work, trench and foundation work, septic systems and seepage.

Unlike centrifugal pumps that rely on water to cool the internal parts, dry pumping will not damage diaphragm pumps. Therefore, seepage in the water that is flowing through the pump does not compromise pump performance.

Using your pump

It's important to know “what and where” you will be pumping, and then purchase the correct size pump with the correct seals for the fluids that you will be transferring.

Remember that altitude will affect pump performance. The higher the elevation, the less lift there is. When choosing a pump, never plan for more than 28 feet for suction lift. I recommend 25 feet of lift as a maximum to have the pump at peak performance.

In addition, because some manufacturers do not sell pump accessories with the pump, it is up to the consumer to know the exact parts needed to fit the pump. Check the pump operator's manual for the right sizes and manufacturer recommendations. Parts to look for include a noncollapsible spiral suction hose, PVC pipe or a collapsible discharge hose, connector nipples, and most importantly, the right sized strainer.

Pump maintenance is simple once the correct pump is in place for the job and the owner is aware of the condition of the pump parts. By continually checking parts for wear and gauging the pump's performance, major repairs can be avoided.

Maintaining performance

The number one cause of poor pump performance is tiny pinholes or abrasions in the suction hose. Trying to pump under this condition is the equivalent of trying to drink from a straw that has a hole in it. Owners and maintenance professionals should check this situation before assuming that a pump has internal problems.

Impeller wear or damage is the second most likely cause of poor pump performance or pump failure. Impeller damage is caused mainly by wear and abrasion, or by passing solids that are too large for the pump. This occurs when the wrong size strainer is used.

Pump owners should learn when it is necessary to visit a service professional.

For example, wear of the impeller, volute housing and wear plates will cause poor pump performance. While the owner can identify those problems, they should be repaired by a professional.

With diaphragm pumps, a hole in the diaphragm rubber is the most severe problem. The pump immediately loses pressure and won't pump as efficiently or even at all. Service professionals must replace the diaphragm if this occurs.

Hard starting and sputtering are signs that the pump's engine might need repair. Engine or motor repairs should be left to the professional, because each engine requires special care and know-how. But similar to an automobile, owners should check the operator's manual for the proper time schedule for changing the spark plugs, the air filter and the oil. Also, be sure the pump has fresh fuel. Use a name brand fuel no more than 30 days old to ensure the highest performance level.

Reddish is a technical information specialist at John Deere Worldwide Commercial & Consumer Division, Charlotte, N.C.