Water accumulator pre-charge

[Dazedkipper]

Can any one recommend what pressure I should pre-charge an accumulator on my fresh water system to?
The pump is a Jabso Par-max 4, cut in 20psi, cut out 40psi.

 

[jimbaerselman]

I used to charge mine (when empty!) to just below the cut-in pressure, on the wild assumption that that would give maximum capacity.