How do I design an eductor-jet or venturi system to rapidly remove the sand from a pool filter? Answered
A friend of mine regularly changes pool filter sand for his clients and asked me to build a more effective way of doing this. So far I think an eductor would work best check this out: http://en.wikipedia.org/wiki/Eductor-jet_pump
1. be able to remove a large quantity of sand suspended in water - approximately 50kg (110 lbs)
2. use a pump to supply the motive force - 3/4 hp pump is readily available
3. the pump MAY NOT VACUUM OUT THE SAND DIRECTLY! that would ruin the pump's impellers instantly. It is essential that the pump only provides a motive force in the form of a fast-running jet of water which will create a venturi effect that sucks the sand/water slurry out of the filter.
4. the "vacuum hose" must be between 700mm and 1m long (27 - 40 inches) and about 1inch diameter.
5. The eductor/venturi must be strong enough to suck a sand/water mixture all the way up that pipe against gravity.
Check the attached diagram and tell me if my venturi design looks reasonable, also what diameters should I have at points 1 - 6?
I also attached a sketchup model of what I'm planning to build
Facilities at my disposal: Welder, drill press, cutoff saw, dremel, various grinders, jig saw.
I DON'T HAVE A LATHE OR MILLING MACHINE BUT IF IT IS ESSENTIAL I COULD ORGANISE ACCESS TO ONE
OK, that's about it. Your commentary is appreciated!