In most drain back solar water heating systems the pump is located just outside the tank and near the bottom of the tank. A U-tube line starts inside the tank near the bottom, goes up over the side of the tank, then drops down to the pump inlet.
When the collectors drain down, the U-tube stays full of water, and keeps the pump primed with water for the next startup. This works fine.
But, if its not possible for the pump to be located at a level near the bottom of the tank (for example its a buried tank), then the scheme shown below might be workable. It uses a priming tank located at the pump that basically supplies water for the next startup and also sucks water up the suction pipe as it empties.
I have never heard from anyone who has used this, so no guarantees that it will work. The ideas is from a handbook on centrifugal pumps by Karassik and Tullo.
Thanks to BBP and the Yahoo SimplySolar group for finding this.
Please let me know if you try this and it works (or doesn't work).
Single Tank Priming Chamber
A single-chamber primer is a tank with a bottom outlet that
August 14, 2013