It's a pretty safe bet that a filter certified to reduce VOCs will also reduce trihalomethanes (THMs). So we asked 3M to test the XL7000 for THM reduction at their own robust testing facilities.
The XL7000 may be submitted to NSF for additional testing down the road, but in the meantime the results from 3M are very useful. In some ways, more useful than NSF can ever be. Here's why:
NSF decides that for a given contaminant reduction claim, the level to start with is one number, and the allowable reduction percentage is another. Based on those two numbers, the certification is granted for only so many gallons of water - usually a very limited amount. Thus the "capacity" of the entire filter according to NSF becomes some very small number of gallons, and that's it, take it or leave it. But this misrepresents the useful life of the filter, and suggests to people that they need to replace it with much greater frequency than is actually the case.
In fact, the ability to reduce a factor like THMs is diminished the more water flows through (assuming that the level of THMs in the source water remains constant). So what we are doing here is simply and directly presenting the numbers, and consumers can decide for themselves what a satisfactory level of THM reduction is.
Note: Testing protocol was using Chloroform (CHCI3). The EPA maximum contaminant level for THMs is 80 parts/billion (ppb). The "challenge" amount, i.e. the amount of Chloroform used for the test, is stated below.
Two XL7000 filters were tested. The reduction percentage numbers below are the average of the two separate tests.
After these using this much the % reduction
many gallons Chloroform (ppb) of the THM
were filtered equivalent was
10 62 100%
500 65 97.54
1000 62 95.81
1500 63 94.60
2000 67 93.96
2500 58 92.93
3000 61 89.34
3500 63 88,57
4000 63 81.75
4500 65 70.00
5000 66 65.15
5500 74 54.73
6000 54 25.93
What does all that mean? Well, an average household of four uses about 3500 gallons of cold water at the kitchen sink per year. So if that household had an XL7000 filtering all the cold water during that year, at the end of the year the system would still be reducing THMs - assuming there really was that much in the water - by 88.57%. The manufacturer recommends replacing the XL7000 cartridge every six months, so if we assume at that point about 2000 or even 2500 gallons of water had been run through the filter, THM reduction would be about 93% at that point in the life of the filter cartridge. Note a much more dramatic fall-off in THM reduction capacity after about 4000 gallons.