The instructions indicate that the comparator block should be used to compare colors. Is it possible to do this without it? Or is a factor from this perspective needed for measurement? The color charts are designed for use with the comparator block. Additionally, when using the comparator block with the blank water sample, a natural coloration of the water is compensated. Therefore, without the comparator block, deviations in the readings should be expected. Do the water tests work at any temperature, or will they show me no value or an incorrect value? Yes, you can use the water tests at both low and high temperatures and obtain accurate measurements. Do my water tests still work even though they have been open for 9 months? In general, opened test reagents have a shorter shelf life than those that are originally sealed. The extent to which the shelf life is reduced depends significantly on the handling and storage conditions of the reagents. Therefore, it is quite possible that after 9 months, a reagent may no longer indicate correctly. However, further information is needed to assess this.