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How to choose the correct submersible pump?

Which types of submersible pumps are there?

There are different types of submersible pumps. The most common in the horticulture are the fresh water, dirty water, dirty water with solids (Vortex), high pressure and a flattening submersible pump.

• Fresh water submersible pump: this is used to pump fresh water, like clean leaking water. This pump always a small quantity of water behind, usually some two to four centimeters.
• Dirty water submersible pump: a dirty water submersible pump is used to pump dirty water, like water containing sand or algae. The pump is suitable for small, compact dirt particles of 25 to 35 millimeters. A dirty water submersible pump leaves a layer of water of four to eight centimeters.
• Solid parts submersible pump (Vortex submersible pump): this is used to pump water that contains coarse dirt particles, bigger than 35 millimeters (larger than a sand grain). What format of dirt particles can be handled by a solid parts submersible pump, varies per type, so take this into account during the purchase.
• High pressure submersible pump: this type is more powerful than a standard submersible pump. This makes the pump also suitable as an irrigation pump or as a pond pump in a silo or basin.
• Flattening submersible pump: in principle this is the same as the clean water submersible pump, only this pump is capable of pumping the water down to an even lower level, to a layer of around three millimeters (mop dry). This is because the inlet is closer to the substrate. This makes the pump suitable for situations where the water must be pumped completely, or at a very low water level.

Please note: some substances should never be pumped. For example:

• Corrosive, flammable or explosive substances (like crop protection agents or gasoline)
• Grease and oil
• Salt water (this may be pumped only by use of a special salt water submersible pump)

Submersible pump with float

The abovementioned types of submersible pumps come in models with or without float. A float ensures that the submersible pump is activated automatically if it is in the water. One can also use a ball float to set the water level, so that the pump will stop automatically when the desired water level has been reached. The advantage of this is that the submersible pump can never run dry this way, provided that the float can move freely. If this is the case, you can always leave the submersible pump on. There are models with external floats (ball floats). These are reliable, but need a lot of space. There are also models with a built-in float (internal float switch?). The advantage of a model with a built-in float is that it requires less space. That is the reason that these are often used in certain manholes . The disadvantage of a built-in float is that it is sensitive to pollution and cannot be adjusted.

Submersible pump without float

A submersible pump without float cannot be set to a certain water level; it will activate at the moment that you insert the plug and deactivate as the plug is taken out. When using this pump you should therefore monitor, making sure that the pump doesn’t run dry. A submersible pump with upper outlet cools itself using the water that is pumped, as this water runs alongside the motor. Once all the water is pumped and the pump keeps running, it cannot cool itself as a result of which it will run dry. Make sure you prevent this, because running dry will cause damage, and burning at worst. This can thus be prevented by monitoring the pump as long as it is on, or by applying an external float(-construction).

Quantity of water to be pumped

The choice for a certain type of submersible pump also depends on the quantity of the water to be pumped. The more water you want to pump, the higher the capacity of the submersible pump should be.

Maximum immersion depth

Every submersible pump has a maximum immersion depth (also called opvoerhoogte ). This is the maximum depth to place the pump at, without it ceasing operation. For most pumps this is seven meters, but there are also pumps that go deeper or less deep. This is dependent on the discharge pressure of the pump. Do pay attention to this.

Connection material

In order to connect a submersible pump, a hose is required. The diameter of the hose depends on the pump connector. The dimension can be found in the specifications of the pump. Also ensure that the hose is long enough. For “household models” you can easily attach the hose using a hose clamp. For larger models with more capacity, the hose is attached by means of a GK-coupling or a PVC-coupling. Pay attention when purchasing aGK or PVC-coupling that it has the correct thread and also make sure whether you require a coupling with inside or outside thread. Please note: a submersible pump is always fitted with an integral plug. If you connect a submersible pump, take into account that warranty will lapse if you cut this plug (for example when you want to lead a cord through a wall).

Points of attention

When using a submersible pump, keep the following points of attention in mind:

• Make sure that the temperature of the pumped liquid never exceeds the maximum. For most pumps this is 40°C, but do always check this in the manual.
• Place the pump on a stable surface.
• Make sure that the suction openings below the pump are not being blocked.
• If you have a pump with a float, make sure that the float can move freely.
• Never lift the pump pulling the electric cable or the float, but use a twine for this.
• A submersible pump may get blocked. Therefore, you should ensure that you regularly check your pumps and clean them if necessary. A clean water pump should be checked for blocking every month and a dirty water pump should be checked every week.

Contra-plug

A submersible pump may become overheated as a result of multiple causes. Better pumps are provided, by default, with a clixon that protects the pump against this. It ensures that the pump restarts automatically as soon as it has cooled down sufficiently. If your pump is not equipped with a clixon, then you can make use of a contra-plug. Acontra-plug ensures that the pump remain deactivated as soon as the pump is overloaded. This way you prevent damage to the pump due to a lot of restarts (which is the case for pumps equipped with a clixon) or combustion (for a pump without clixon).