We have been here before with this sort of thing,Usually with either vacuum cleaners to industrial pumps.
I will repeat what what i have said before.
Modern demijohns are not pressure vessels,
They can easily implode under a strong vacuum.
The Idea of pulling a vacuum in a demijohn is both...
As Chippy says it IS cheaper using supermarket juice.
Rather than cider i make white wine from it,
Very nice it is too.
TBH i don't know how they can do it at these prices as when you think of the amount of apples needed for a liter of juice.
Ha ha on a good day i still think i am 18 athumb..
chasing the birds is what young men do.
That said the amount of attention i used to get from the local lasses was embarrassing.
All a long long long time ago,wink...
I agree with Chippy those two part finings will clear just about anything.
Also as Mikes 1992 has pointed out wine in the bucket will look darker than in the bottle.
Since you make beer the thing that is different is beer ferments quickly whereas wine can rumble on for what seems an eternity...