We're going forward on this and getting firm quotes on RO systems... so Martin, if I spec something like <50ppm TDS, and single digits on all ions like Ca, Na, Mg, Cl, SO4, etc, that would be reasonable?
And what about alkalinity and bicarbs?
And what about pH, do I need to worry that the pH of RO water is slightly acidic?
I believe RO presents no RA, Bicarbonate or pH issues, since it has been stated that if you use RO for sparging, you don't need to treat it regarding pH concerns. Based on that, I build my strike water from RO and sparge with straight RO - but caution should be used if you are not batch sparging or no sparge brewing. Fly sparging can extract tannins, if you get too low on the gravity (below 3 Brix, IIRC).