Orange County · chlorine byproducts

Chlorine byproducts in Orange County tap water.

FilteredWTR has chlorine byproduct results for 9 Orange County water systems from their latest water quality reports. Four of them run at or above half the federal limit for total trihalomethanes, and the highest is 53 ppb in Irvine, 66% of the 80 ppb limit. No result reaches the legal limit for either byproduct.

How chlorine byproducts form

Utilities add chlorine or chloramine to treated water so it stays free of bacteria all the way to your tap. The disinfectant also reacts with natural organic matter left in the water, such as bits of decayed leaves and soil, and that reaction forms disinfection byproducts. The EPA regulates two groups of them. Total trihalomethanes (TTHM) are capped at 80 parts per billion and the five haloacetic acids (HAA5) at 60 parts per billion, because long-term exposure is associated with health risks.

Disinfection is what keeps waterborne disease out of the tap, and the EPA rules leave it in place while limiting the byproducts. Compliance is judged on a running annual average at each sampling site.

Byproduct levels by city

Verdicts use the same scale as FilteredWTR city reports. Good means the average sits under half the limit. Caution starts at half, and Too high means the average reached the limit.

Total trihalomethanes (TTHM)

Haloacetic acids (HAA5)

Haloacetic acid results run from 10 to 19 ppb, which is 17% to 32% of the 60 ppb limit. None of them reach half the limit.

Byproducts in the shower

Trihalomethanes evaporate easily, and hot water speeds that up. In the shower you breathe the steam while your skin absorbs some of what is in the water. A 1996 exposure study in Environmental Health Perspectives measured chloroform, a common trihalomethane, in people after ten-minute showers. Breathing the steam and skin contact each delivered an internal dose in the same range as drinking the water. The study measured exposure and left health outcomes at typical tap levels untested.

Activated carbon at the sink or for the whole house

Activated carbon is the standard tool for chlorine and trihalomethanes. As water moves through the carbon, those compounds stick to its surface. For drinking water, look for a filter certified under NSF/ANSI Standard 53 with TTHM listed on its certificate. Standard 42 covers chlorine taste and odor.

A point-of-use filter mounts under the sink or on the faucet and treats the water you drink and cook with. It leaves the shower untouched. A whole-home carbon system sits where the main line enters the house, so the shower and every other fixture get filtered water. It costs more up front and needs a tank sized to your household's flow, and its carbon gets replaced on a schedule set by how much water you use.

A citywide average comes from sampling sites spread across the system. The free in-home test measures chlorine at your own faucet, and the tech can walk you through whether carbon at the sink or carbon for the whole house fits the way your family uses water.

Sources: U.S. Environmental Protection Agency, Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules · Environmental Health Perspectives (Weisel & Jo, 1996), Ingestion, inhalation, and dermal exposures to chloroform and trichloroethene from tap water · NSF International / American National Standards Institute, NSF/ANSI Drinking Water Treatment Standards. Byproduct figures come from Orange County utility water quality reports compiled by FilteredWTR.

Related guides: Lead in Southern California tap water · Hard water in Orange County · Water systems with EPA violations · All city water reports