Low Voltage Water Pumps

The pros and cons

using a low voltage pump in your water feature

Most pumps used for garden water features such as fountains and ponds run from the standard power supply (100 - 127V in the Americas and Japan and 220 - 240 in the rest of the world).  As long as the pumps and wiring are installed correctly and maintained regularly they should be as safe as any other electrical installation. 

However, if you are unsure then you can get low voltage pumps that operate from a 24 volt supply, though the range of sizes available is limited.  These low voltage pumps were commonplace when submersible pumps first came onto the market, and people were very nervous about putting a standard voltage pump into a pool of water.  Apart from any other considerations, they did not want to electrocute their fish that, in many cases, cost more than the pump!

However, as pump design improved, their excellent safety record gave people more confidence in them, and today low voltage pumps are very rarely used and available only in a limited range of sizes.  Standard voltage pumps are constructed by flooding the parts of the pump with non-moving parts with a liquid resin that sets and insulates all of the exposed electrical parts.  In a standard voltage magnetic pump, the only moving part is the impellor that is housed outside the casing that holds the electrical parts of the motor, and so the pump is completely safe.

Were such pumps not safe, the papers would be filled with tales of electrocutions of people and fish.  Since such tales do not appear, then by definition the pumps must be safe.

It is difficult to see, then, the benefits of using a low voltage pump.  If you have such a pump, you also need a step-down transformer to reduce the voltage to 24 volts.  This has to be kept in a dry places such as your home or a garage. Your pump then has to be sited no more than 50 metres from the transformer, since the voltage can drop over distances above this to render your pump inefficient.

The low voltage pumps are expensive in comparison to a mains operated pump, and if your home is protected by a RCD system, then the higher powered cable will not present much of a hazard to you, even if you cut through it.  However, if you are installing a pump in an area where the supply is all at low voltage then the low voltage pump might be necessary.  For example, if you have a low voltage model railway that you are running round a pond, the low voltage pump can be fed from the supply already there and prevents you from having to run a high powered cable to the installation.

Another reason for using a low voltage pump would be if there is the likelihood of children playing around the area.  Although they, too, should be protected by an RCD system, you will probably have more peace of mind in using a low voltage.  This might also be true in the event of the pump being installed in a high traffic public area.

The term ‘low voltage pump’ can refer to more than just the 24 volt AC pumps that operate with the same power as the higher voltage pumps, but also to DC pumps that can be run from standard 12V car batteries or by solar power.  These too are used in garden water features, though many run from the mains supply and use transformers to drop the voltage and rectify the current to DC.

This type of low voltage is very handy where the volume of water to be moved is small, or only small distances are involved, and they are very safe for use even where children are playing.  Where cost is a consideration, the DC pumps are generally the least expensive, and where larger volumes of water are involved, or it has to be raised to higher heights, the full powered pumps come next in the pricing stakes with the 24V low voltage pumps the most expensive.

The only real benefits of a low voltage pump, then, are where it is possible to accidentally cut into the supply cable, and the disconnection of the electrical supply by the activation of an RCD system would be extremely inconvenient.  A low voltage pump would also be a viable option where there is already a low power system in use and there is power to spare to allow the pump to be wired into the circuit.

Other than that, the full power pumps are less expensive, do not lose power if the supply point is some distance away from the pump and are generally more robust.  Although low power pumps are available on the market, then, they are restricted in use and the availability of the 24V pumps will probably fall off, as that of the lower powered DC solar pumps will increase.