The garden pump does not suck

Many garden owners have their own well, which is to be operated with a garden pump. But again and again there is the problem that a garden pump does not suck in water. Therefore, we have created a kind of checklist for you in case your garden pump does not prime.

The rotary pump has long since become obsolete

In the past, swing pumps were usually found in gardens, with which you had to pump the water from a well into a fountain. Garden pumps have long since ceased to be particularly expensive and offer much more comfort. But once the garden pump has been installed, suddenly it stops being able to pump water.

Typical pumps as a garden pump

Before we go into details that may be responsible, let's first differentiate between the different pump types:

  • centrifugal pumps
  • Submersible pumps (submersible pumps are also centrifugal pumps)
  • suction pumps

The centrifugal pump is actually not self-priming

Centrifugal pumps are basically not self-priming according to their functional principle, but can be built in this way. Then these pumps have a pump housing which is sealed to the intake manifold or intake. There is usually a so-called foot valve, which is nothing more than a one-sided lock or check valve. If such a pump is now filled with water, the water collects in the pump housing.

The suction line equipment depends on the previous pump

But now it is the case that fountains usually extend several meters deep into the ground, so there is a correspondingly long suction line. In modern intake pipes for wells, therefore, such a foot valve is also attached to the lower end of the intake manifold, so that it always remains filled with water. However, there are intake pipes that may not have been equipped because they were equipped with a suction pump (piston pump).

It is imperative to bleed the suction lines, even with a self-priming centrifugal pump!

In this case, the water can only be sucked in by means of a centrifugal pump if the entire intake is really filled with water. Even a partial filling is not sufficient because the gas or air content in centrifugal pumps must never exceed eight percent. But depending on the pump, just a few percent of air can become critical.

The suction line (head water column)

In addition, you need to keep in mind that a pump can not deliver more than eight to ten feet of water in an open system. A water column of ten meters corresponds approximately to the atmospheric pressure in which we live on Earth. The range between the atmospheric pressure and zero pressure is called negative pressure. Any pressure below zero, on the other hand, is a vacuum that can not be produced by a pump under the given circumstances.

The suction line is longer than the pump head

But since the effectively effective pump efficiency is always less than 1 (less than 100 percent) (pump efficiency minus hydraulic friction loss at the pump and minus mechanical friction loss through the drive), even good pumps are limited to a head of about 8 meters of water. You must not equate the height of the water column with a geodetic height difference (normal height difference). The height of the water column refers to the length of the intake pipe with the feed wheel.

For longer delivery lines integrate valves

Longer lines can only be overcome if appropriate check valves are installed. In the technical application but often cascade pumps are used, so several pumps in a row. On the data sheet for your pump, the head (height of the water column) should be specified. This height must never be exceeded in the length of the intake pipe. Also crucial, however, is the diameter of the pipe capacity to be sucked in. The pump data sheet shows which diameter must not be exceeded. The pipe diameter is given in inches, as with all pipes.

The tightness of the suction area of ​​the pump

Finally, there are still mistakes in the installation of a new garden pump. The intake system must be absolutely tight. Even the slightest leak causes cavitation in the impeller or impeller area. Under cavitation, the formation of ever larger gas or air bubbles in or on the impeller is described and explained. Depending on the impeller, these air bubbles have the property of collecting on the impeller and thus negatively influencing the delivery rate.

Checklist if the garden pump does not suck

For all the reasons mentioned above, this results in a checklist. We sorted them from simple to complicated (descending), so you can really work them off in sequence, always with the most likely causes, which is why your garden pump does not suck:

  • wrong pump (self-sucking, not self-sucking - beware of supposedly self-priming centrifugal pumps - when connecting to the suction line, also fill the suction line with water
  • Open the suction opening of the pump and fill it with water (Operating Instructions)
  • Fill the suction line in front of the pump with water (not self-priming pump, but not centrifugal pumps with valve housing closed by the valve!)
  • Connection at the intake not tight (hemp or Teflon for sealing the thread)
  • Leakage in connected, multi-part intake manifold
  • for pumps with filter on the intake possibly leaking filter
  • too long suction line in the well (comparison pump height according to the data sheet and length suction line, which is limited to 5 to 8 meters depending on the pump)
  • defective closure valve when self-priming centrifugal pump declared
  • missing or leaking foot valve at the bottom of the suction line

So it can be fast that you have connected the wrong pump or a pump is described as confusing (the self-priming centrifugal pump has only a closed pump housing filled with the fluid and the suction must be directly into the fluid to be sucked). In about 90 percent of all non-priming garden pumps, however, a leak in the intake is responsible.

Tips & Tricks

Of course we offer you in the house journal even more articles about pumps. So also to the function of submersible pumps, as it can also be enormous differences against. Some can be used as a garden pump submerged in the fluid, others not.

Video Board: Seawall pump tips, trick to prime using a check valve and foot valve