Check the documentation for your tester like Rhizome said. Depending on the tester, you may only need one calibration solution, or, you may need all 3. If it takes all 3, I would definitely use all 3.
gainesvillegreen Reviewed by gainesvillegreen on . Ph buffer solution preferance After waiting 3 weeks I just received my ph tester but they didn't ship me any buffer solution and since I'm new to this I didn't even know you needed it. My question is which buffer solution is best. My tester states there are 3 kinds, #4, #7 and #10 which I have no idea what the difference is. I have to order this so I'm hoping someone can give me their input on what is best. Rating: 5