Just recently purchased new filters/membrane for my AWI 75gpd ro unit. Purchased a brand new hand held TDS meter as well. Regardless of what we test it in bucket, freshly washed cup, we're still getting a reading of 3. Any ideas as to what it could be? We're pretty sure the lines are ran properly as well as the filters in the proper place. What kind of container are you guys using to test your water in?