What Is The Reason For The Lack Of Suction in A Self-priming Pump

Dec 12, 2025

Self suction pumps without suction need to be considered from two perspectives: one is the newly installed self-priming pump, and the other is the self-priming pump in use. Different perspectives lead to different ways of dealing with problems. Let's take a look at how to handle it below?

 

1, What's wrong with the newly installed self-priming pump having no suction at all

 

There is a high probability that the newly installed self-priming pump has no suction force due to air leakage in the inlet pipeline, or the user may have enlarged the inlet pipeline during installation and made it too long. It is also possible that the user did not understand the use of the self-priming pump and did not add water to the pump chamber. Another possibility is that the self-priming pump motor has reversed. By investigating these possible reasons one by one, the cause can be found. It is difficult to investigate the reasons for the leakage of imported pipelines. If it is a steel pipe, we recommend conducting a pressure test or negative pressure test after welding before installation and use. If it is a hose, we recommend installing a blind head at both ends and installing a three-way ball valve and vacuum gauge in the middle of the exhaust pipe. Then, a vacuum pump should be used for negative pressure testing. After the negative pressure is drawn to the limit, close the ball valve in the middle of the exhaust pipe and observe whether the vacuum gauge drops. If there is a drop, there must be a leak. Then, you need to carefully observe it yourself. If the environment is quiet, you can hear the sound of the leak point inhaling into the pipeline, which is particularly obvious. Find the leak point and repair it.

 

 

It should be emphasized that some users, when using ordinary self-priming pumps, encounter situations where they cannot suck up liquid. Many users are accustomed to dismantling the inlet of the self-priming pump and placing their hands at the inlet to sense whether there is suction. When they place their hands here and find that the self-priming pump has no suction at all, they think it is a problem with the self-priming pump. In fact, this method is incorrect. First of all, it should be known that this ordinary self-priming centrifugal pump does not have a super fast suction speed like a vacuum pump. This self-priming pump can only slowly remove the air in a fully enclosed pipeline until it reaches a certain negative pressure before the liquid can be sucked up. When you dismantle the inlet pipeline, it is equivalent to a self-priming pump. Connected to the atmosphere, you cannot sense any suction force with your hands, Because the self-priming pump is already in a state of sucking a large amount of air, it can no longer generate negative pressure.

 

2, What's wrong with using a self-priming pump for a while without any suction

 

If a self-priming pump that has been used for a period of time suddenly loses all suction, please check whether the self-priming pump chamber and impeller are blocked. Many users are afraid to open the pump for inspection when they encounter water suction failure due to insufficient understanding of the internal structure of the self-priming pump. Therefore, we recommend that users continue to explore and let the operators understand how to check whether the self-priming pump chamber is blocked. If there are a large number of impurities blocking the impeller, there will definitely be no suction. Therefore, during maintenance, it is necessary to first cut off the power and close the inlet and outlet valves, open the drain bolt at the bottom of the front of the self-priming pump body, drain the water in the pump chamber, and then remove the motor. Remove the foot bolts and separate the coupling, For the direct connection type, simply remove the bottom corner bolts of the motor, and then remove the ring of bolts on the pump cover to remove the bearing seat and impeller together. After removing them, you can see if there are any blocked debris on the impeller.