ph/ec household product checks. (HELP!)

i just got this used $50 meter but it loses it calibration every day. are there household items that have a set ppm or ph that i could calibrate it to? like for example is there a set ph for hydrogen peroxide or pure lemon juice or something like arrowhead water? haha.

How do you know it is losing calibration? Do you have TDS Calibration solution? If not, buy some. If it's battery powered, replace them. You should be good to go.

HTH