Rental Pump Maintenance: How to Ensure Optimal Performance for Bypass Applications

Proper maintenance is critical for long-term, efficient utilization of bypass pumps. Without employing best management practices (BMPs), you put your project at risk. Rain for Rent Pump Shop supervisor Mike Thomas and SWAT (Sewer & Water A-Team) manager Dick Pilotte shares some tips and BMPs to ensure your pumps are operating at their best.

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Service & Checks

Each pumping unit should be serviced every 250 hours of operation, which includes a basic oil and filter change. Due to the frequency, this service often happens in the field. When the pump comes back to the yard after the job has concluded, several additional checks should be performed on the mechanical seal, the coupling between the engine and pump, and the discharge swing check or flapper valve. The oil in the mechanical seal is also important to check to ensure no cross contamination occurs. The faces of the seal need to remain lubricated properly to prevent unnecessary wear. The bearing temperature should also be checked to confirm they aren’t getting too hot under normal operating conditions.



Testing the clearances between the impeller, wear ring and wear plate is important to maintain proper pumping efficiencies. If the clearances between the impeller and wear ring are outside the required specifications, the pump will start to recirculate within the volute. You won’t be able to pump the full volume or pressure of water that the pump is designed to handle and water will bypass the impeller instead of going out the discharge.

When the pump is returned from a job, it should undergo a vacuum test to ensure it will pull and sustain 24-in. Hg of vacuum. If the pump can’t pull at least 24-in. Hg of vacuum or if the vacuum plate cannot be held in place, the pump won’t perform in the field and you will know other repairs are needed. By testing the pump’s vacuum each time it comes off a job, you’ll know if it will meet the required suction condition and will pump at the necessary flows specified for the project. If there are issues with generating and sustaining vacuum, you risk pumping less water, which will cost you more in time and fuel.

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Dynamic testing is recommended after the pump has been on rent for any length of time. Dynamic testing requires that the pump be set up to operate for three hours under design conditions at a testing facility. This will ensure the pump performs to the pump design curve. In addition to testing the pump end, dynamic testing ensures the engine is in good order and there aren’t fuel or radiator leaks. Running the pump for a few hours during peak temperatures is a practical way to ensure the system works in the heat of summer or freezing temperatures of winter.

When dealing with mobile equipment versus permanently installed pumps, it’s important to also check the engine and mounting hardware. If the engine and pump end are out of alignment, the bearings will wear prematurely. As bearing wear increases, more heat is generated. Proper greasing will help reduce bearing wear. Checking bearing temperature regularly provides an early indication that something might be out of alignment or other problems exist.

What to Ask When You’re Renting a Pump

When you are in the market to rent a pump, make sure you ask about the company’s service practices:

• What does the service entail?


• Who is responsible for service?


• Is there additional maintenance that is needed?


• Is the pump vacuum tested regularly?


• Can the pump run dry?

If the pump can’t run dry, the pump end can potentially seize up in certain suction conditions and you’ll likely be responsible for the cost of repairing the unit, which could be thousands of dollars.

In-Field Bypass System Maintenance

In addition to the pump maintenance described above, one of the biggest things you can do to ensure your bypass system is performing is to keep the priming system and pump clean and free of all the items that go down the toilet- including toilet paper, rags, mop heads, and even random things like swim suits and dentures. When a pump starts to clog up, it won’t pull a proper vacuum. You’ll know this is happening when the pump’s flow starts to decrease and there’s a drop in the vacuum and pressure gauges. It’s also easy to hear; the pump will start to make a different noise and will start vibrating and shaking.

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Pumps should have cleanouts that are easy to access. This five- to 30-minute job may need to be done frequently, or could wait until pump operations shift change. Waiting until shift change gives you additional support on site to clean out or de-rag the pumps while other personnel monitor the bypass. System backup pump(s) play a critical role during downtime for de-ragging, allowing the bypass to continue operating while managing the risk of an overflow.
Another easy way to ensure smooth pump operation is by supporting pipe with cribbing to keep the weight of the pipe and water off the pump itself, maintaining the pump’s alignment to the engine.

Lastly, preventing the floats from getting sucked into the suction or debris from wrapping around the float is important. For easy access and maintenance to the floats, connect the float wires to a slotted angle iron steel tee (12 or 14 gauge) to the top part of the manhole using just enough wire to allow the floats to operate.

Proper pump maintenance and employing a trained bypass pump operation crew will help your bypass system perform as designed. By following the tips and suggestions above, your next job will be sure to run effectively.

Julie Doris is corporate communications manager at Rain for Rent.