Others will most likely pass through the filter unaffected. As noted above, activated carbon will remove a variety of substances from water. Note the wide range in performance. Most manufacturers list a removal rate for trihalomethanes up to 99 percent but Table 1 shows that only he best line by-pass units were capable of this rate for an extended time. All other types showed much lower removal and the average for even the line by-pass units was only 62 percent.
Manufacturers tend to report the best removal rate of which their unit is capable.
The values are frequently the amount the unit will remove at the beginning of use for a single contaminant at moderate concentrations. Results of testing by other groups vary. Some, such as those in Table 1, are averages for the stated life of the filter while others report removal rates for various amounts of use. In any case, it is unrealistic to expect that any test will include exactly what you have in your water. The buyer must, therefore, be guided by general principles and limited testing.