Overview The Mavea temporary hardness test kit is an incredibly accurate way of testing carbonate hardness of your water. It's a very easy test kit intended to prevent scale build-up in your machine by accurately monitoring water quality or hardness. We recommend a hardness of 3 grains. How-To Use the Carbonate Test Kit Fill the measuring vial (the clear tube pictured above) with the water you intend on using in your espresso machine. Fill to the 5 ml mark on the vial Add the Mavea solution a drop at a time (counting each), gently mixing by swirling the vial after each drop Once the color changes from purple to yellow stop adding the solution Count the total number of drops used. Each drop is equal to 1 grains per US gallon. Example: You used 4 drops in the vial of 5 ml of water and the color changed. The grains per gallon would be 4.
