A way to modify an old pool pump to become a very powerful vacuum device capable of drawing up course sand from teh bottom of the pool.
The standard is barely able to draw sand off the bottom, but my mod to the old unit did an amazing job.
Not sure how long this will last, but re-wiring the coils of the pump motor in parallel, beefing up the power cabling, setting in a "venturi effect" filter bag to catch the sand ...
I am happy.