Quote:
Originally Posted by Coasting
Oh that's pretty cool. I didn't know ones with cords that only turned on when the power went out even existed. I know what I'll be buying!
I'm having trouble picturing how that pvc tube works.
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Yes, the electrical cord that plugs in goes to a small relay inside the pump. As long as the cord is plugged into the wall, the set of contacts that completes the circuit to run the pump from the D cell batteries are held open. Once the outlet the cord is plugged into loses power, the contacts close, completing the battery circuit et voila, the pump runs on the batteries. Similar concept to what happens in a UPS, but much simpler.
As for the air lift, the wiki I linked to doesn't explain the principle well enough?? The only difference in the article graphic Figure 1 is that they have the air supply line feeding through the vertical tube at the bottom through a bulkhead. My gizmo photo has the air supply tube fed through a hole in the top of the elbow. Works the same way. Of course the wiki article also goes on to show the modified/improved geyser version. The advantage to the version in my photo is the air tube can be adjusted up or down inside the pvc tube to fine tune the air lift effect. The version shown in wiki with the tube entering the bottom in a fixed position does not allow for that.
EDIT: One more thing to note, although I did explain in my original post about airlifts, is that in our case, the opening of the elbow at the top of the assembly will be half submerged. In the wiki figure they show the elbow above the water surface. Their application has the water being pumped/lifted out of the tank. In our case, with the elbow half submerged, the water is discharged back into the tank at the surface, creating a moderate flow.