I bought mine used I would try it. water is usually 7.0

just soak it in water(I don't think you need that solution)...I store some water in cap to keep electrode filter wet. I would ask a hydro shop guy...I am sorry...I know I recommended that pen, but I got mine used off ebay 1-1/2 years ago and never have used the calibration solution...It came calibrated. let me know if this helps...If not I will look into it, by asking a hydro store friend...peace
p.s. I have dropped mine and all kinds of stuff...It has held up over time, and my hydro store have totally switched to milwaukee after having alot of service problems with Hanna...
latewood Reviewed by latewood on . which Ph pen? Im looking at buying one and not really sure which one is good. Any suggestions? Thanks. http://cgi.ebay.com/New-Accurate-DIGITAL-pH-METER-Hydroponics-Hydro-Tester_W0QQitemZ220007726612QQihZ012QQcategoryZ75670QQcmdZViewItem http://cgi.ebay.com/Milwaukee-Digital-pH-TESTER-Micro-Brewing-Wine-Making_W0QQitemZ180007762838QQihZ008QQcategoryZ38172QQrdZ1QQcmdZViewItem http://cgi.ebay.com/NEW-Milwaukee-pH51-Waterproof-pH-meter_W0QQitemZ230009360338QQihZ013QQcategoryZ58191QQrdZ1QQcmdZViewItem Rating: 5