Magnetic Drive Water Pumps

If you are thinking about water cooling, you will need a pump. The most popular units are the submersible fountain pumps. There are two basic type to consider:

1. The Magnetic Drive, and
2. Shaft Drive pumps.

Shaft drive pumps are the more traditional of the two – they consist of a water-proofed motor driving an impeller on a central shaft. Water integrity is by seals around the shaft – over time these will eventually wear out. Beckett is a major manufacturer and guarantees their pumps for two years.

I spoke with one of their engineers and they build their pumps on the assumption that they will run continuously. They have no data on intermittent operating life.

Magnetic Drive pumps consist of three basic parts:

• A power unit encased in water-proof epoxy which creates a magnetic field;
• A magnetic ceramic impeller, the only moving part;
• A housing for the impeller and hose connection.

These pumps are supposed to be virtually maintenance free as they have no seals to wear out. However, I noticed that the guarantees are shorter than the Beckett pumps – usually one year.

Only 3 basic parts – housing, impeller shaft and “motor”.

If you look closely at the shaft (not visible here) you will see that the shaft is more complex than it looks – it appears to be two shafts – a central shaft fixed in each end of the pump, and an outer shaft to which the impeller is attached. This outer shaft is magnetic and is driven by a “rotating” magnetic field, lubricated by the water in which it is immersed.

As simple as it looks, it is still subject to wear over time. I also noticed that Mag Drive pumps tend to be noisier – I think it is due to the relatively loose fit of the two shafts (necessary to allow water to act as the lubricant). Noise however is relative – compared to intake and power supply fans, you should not hear the pump.

The shaft inside the “motor”.

As the picture below shows, these pumps are not big – this size is typical of pumps in the 50 – 150 gph range. A one or two quart container will totally enclose the pump, and resting the container on sound-absorbing foam will virtually ensure that pump noise will be nil.

These units are not big – about 3″ (80mm) all around.