A Case Study of Self-Priming Monoblock Pump is not Working


Client: Individual Client at Baroda, Gujarat State, INDIA

Complain: The pump was tripping

LUBI MDH-25E self-priming pump
LUBI MDH-25E self-priming pump


The MDH-25E is a self-priming pump, especially designed for application which requires robust performance under extreme conditions. These pumps can be used at:


  • Residential bungalows
  • Car Washing
  • Sprinklers in lawns and gardens
  • RO water treatment plants
  • Community water supply


Our client owned an apartment in a high-end residential society at Baroda. He had installed our MDH-25E self-priming pump to boost the water pressure in his house, as it was inadequate.

However, one day when he attempted to turn on the pump, it tripped. After several attempts with the same result, he realized that something was amiss and immediately contacted us using our toll-free helpline to register a complaint.



  1. Customers can register a complaint by calling our toll-free number, after which they will receive a text message with information about the complaint as well as the contact details of our service engineer.
  2. Our engineer usually calls up to fix an appointment as per the electricity schedule of the area, as there are frequent power disruptions in some places.


At the appointed time, our service engineer arrived on location and started the preliminary checks to determine the problem. The following steps were taken:


  1. Using a clip-on meter, the service engineer checked the power supply to the pump, and then opened the terminal box to ensure that the power was reaching the motor's terminal. 
  2. The service engineer attempted to turn on the power supply, but it immediately tripped.
  3. The service engineer then used a screwdriver to check the fan (located behind the pump), but it didn't move.
  4. He then removed the pump from the pipe fittings and opened it to further examination.


Lubi Self-Priming Monoblock Pump nameplate
Nameplate Of The Pump


After conducting a detailed inspection, our technician found that:

  1. The voltage from the main power supply was at the correct level, ruling out the possibility of tripping due to high or low voltage fluctuations.
  2. When the engineer opened the pump, he found the impeller broken. This could have been because of some external debris entering the volute of the pump.


Broken Impeller
Broken Impeller


Our engineer concluded that the damaged impeller was the reason for the problem (the pump not working) and advised the customer to replace it with new one.

The customer agreed and the damaged impeller was replaced with a new one. Thereafter, the engineer installed a new strainer on the suction side to prevent any debris from entering the pump.


New Impeller
New Impeller


After the installation, the technician carefully reassembled the pump and refitted it to the pipeline.

He tested the pump to ensure that it was functioning properly. This time, the pump ran smoothly without tripping, just as it had been working before.




To ensure optimal performance of your self-priming pump in areas where water quality may be a concern, it's important to take certain precautions.

Installing a strainer (mesh filter) before the suction pipe is highly recommended as it can help prevent external debris from entering the pump and affecting its performance.

This simple step can go a long way in maintaining the longevity and efficiency of your pump.

Frequently Asked Questions (FAQ’s):


Q. What is the recommended power supply for the single-phase MDH-25E self-priming pump?

A. The ideal power supply for the single-phase MDH-25E self-priming pump is 180 to 230 volts.


Q. What is the purpose of a strainer?

A. A strainer is a device that helps to prevent unwanted particles from entering the pump along with the water or liquid. This helps to protect the internal parts of the pump from damage.

However, it is essential to ensure that the strainer does not get clogged, as this can cause other problems.


Q. Why is it not recommended to use self-priming pumps at construction sites?

A. Construction sites often have water that is contaminated with external debris, making it difficult to prevent the debris from entering a self-priming pump.

Even if you install a strainer to filter out the debris, the strainer may get clogged and require frequent cleaning, which still does not guarantee that the pump will perform normally for long.

As a result, it is best to avoid using self-priming pumps at construction sites to prevent damage to the pump's internal parts.

Recommendations :


The following measures can ensure that your self-priming pump lasts longer with little or no downtime.

  1. Always ensure your MDH-25E self-priming pumps get continuous (Single phase) power supply of 180 to 230 volts.
  2. The winding and insulation of the pump should be regularly checked using a megger meter.
  3. Our self-priming pumps can lift water to a height of 6 meters (approximately 18 feet) without the need to fill the suction line with water.
  4. Any kind of leakage can impact the flow and pressure. It is advisable to check the nuts and bolts of the pipe, to ensure they are tightened properly.
  5. Presence of external debris anywhere in the pipeline or the pump apparatus can impact the pressure / flow of water.
  6. Self-priming pumps work better with soft water rather than hard water.
  7. The Non-Return Valve is a very critical component to ensure the smooth functioning of the self-priming pump. Therefore, it is very essential to install the NRV carefully and at the right location.
  8. Always check the movement of fan (behind the pump) before switching on the pump. It should not be jammed or obstructed in any manner and should rotate clockwise.
  9. Always run the pump at the duty point as declared by the company.
Final Words :


It is advisable to follow the guidelines provided by the dealer while buying or repairing the pump.

You may also refer our user manual or call our toll-free number for assistance.