I have had battery backup air pumps in the past. The problem is that they
blow diaphragms or other parts that are not available to make repairs.
After my problem last week with the GFCI, I decided to try to see what I
could do. I have scouted everywhere for the parts, to no avail. Today I
bought an inverter, and an auto battery. I already had a battery charger.
The battery charger will keep the battery at full charge, and the inverter
will convert the 12 volt to 110. In to the inverter, I plugged in my air
pump that is really large, draws about 80 watts. By my calculations, I
should have about 18 hours before the battery discharges, and that will
definitely give me time enough to see that I don't have power to the pond.
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RichToyBox
http://www.geocities.com/richtoybox/pondintro.html