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The Garden FAQ Index |

Low voltage ac water pump for garden railroad?

While bilge pumps are only meant to be run a very short time, a bait bag pump (e.g., Jabsco) puts out a lot of volume, has standard garden hose attachment, and can be run for hours and hours on end (as long as it doesn't run dry). These also run on 12 volts dc but consume a lot of current. I have been toying with this idea as I always see these fairly cheap at swap meets but was concerned about the high current draw.

Todd Brody
November 04, 1998

Jim, I have found 12volt bilge pumps work but they tend to have short life for some reason (only meant to run intermittantly?) Low voltage AC motors are rare so you will probably need to use DC. Also note that most small pumps are 'vane' types and do not pump very well if the full motor speed is not available. In your case you could use this feature to get the little bit of water you want to pump by using a 24 volt bilge pump and a diode and capacitor so that the motor will get about 16 volts DC.
When converting from AC to DC use the following to work out what voltage you will get.
AC to DC via a bridge rectifier(full wave rectification)-:
ACvolts x 1.414 - 1.2 = DC volts.

AC to DC via a single diode(half wave rectification)-:
ACvolts x .707 - .6 = DC volts.

If you put a capacitor on the DC side make sure it is rated for around 100% over the AC voltage. IE 18Vac, capacitor should be at least a 35 volt type, preferably a 50V type.

Ron Powell
November 04, 1998

Credit for information from the following sources: Denver Botanic Gardens, MSU Extension Office, Colorado State University Cooperative Extension