I bought a pack of hach test strips for water hardness, intending to see how quickly a Brita filter became ineffective in softening my city water. I also tested a gallon of distilled water with TWW espresso powder added to it and was surprised to find the hardness much higher than expected.

I then checked pure distilled water and got a hardness of about zero, then added TWW to that gallon, shook it, waited a day, shook it again, and tested. See the results below, where the hardness is again higher than recommended for long term machine health.

It seems that either the strips are inaccurate or the TWW is adding more than it should be. Thoughts?

That looks a little odd to me. Be sure that you didn't use the 5 gallon packet on 1 gallon of water.

Also, if you have a TDS meter, do a reading with the water at about 25℃. At least initially, the TWW folks were focused on making the recipe come out at around 150 ppm when read by the ubiquitous inexpensive (NaCl calibrated) conductivity 'TDS' meters.

Thanks for the reply.

It is one packet for one gallon of water.

I don't have any other meter, and am inclined to distrust the accuracy of the strips. But now I can't do my experiment with the Brita filter.

Bummer