Really need to calibrate meter as its been probably nearly a year haha. Can't get any hanna solution in my country, ordered meter off amazon. Not sure about trying to bring shit like that in our border, customs might not like that. Could get the powder shit from uk, would that work? Can i just use any old solution and the hanna will read as solution and calibrate? its 4.01 and 7.01 correct? So if i used 4.0 and 7.0 it would only be 0.01 out? I think i could handle that..