What can I do to lower the THMs at my tap?

THMs are volatile organic compounds. That means they desire to release from the water into the air, similar to the way carbonation in a carbonated beverage such as soda or seltzer water releases into the air when you first open the bottle. The City of Napa performed a small experiment at the treatment facility and analyzed several samples after they had been handled the common ways a customer might fill a glass of water to drink it in their home. This is only one experiment, but shows the nature of the reduction of THMs.

Each entry below was handled as described, then poured into a sample bottle with no head space per analytical protocols and analyzed for THMs.

FROM FAUCET DIRECT87.6
FROM FAUCET INTO GLASS, SITTING FOR 5 MINUTES67.7
FROM FAUCET THROUGH A BRITA FILTER64.8
THROUGH A REFRIGERATOR FILTER54.4carbon filter for GE Model #PSC3RGXCFSS, Filter #WF282 GE MSWF
THROUGH AN INLINE FILTER UNDER THE SINK FROM FAUCET2.7

4 filter (GAC) R/O system, Sierra Model NS-1N30-00 by Nimbus Water Systems


Note this is one side by side study employing standard laboratory sample techniques. The City of Napa does not recommend one filter manufacturer over another, nor does it guarantee the effectiveness of any home filter devices. All home water filter systems need regular maintenance to operate effectively. The effectiveness of filter brands is tested by the National Science Foundation (NSF). For specific information about your filter, contact the manufacturer.

Show All Answers

1. I’ve never heard of disinfection byproducts before, so why am I hearing about this now?
2. Why do we need to add chlorine to the water?
3. What is a THM and how is it formed?
4. How much is a ug/l?
5. What about other water systems?
6. What can I do to lower the THMs at my tap?
7. Are personal home filters effective?
8. Should I drink bottled water instead?