Sherry Miller took a swig at the Post Falls Library's drinking fountain on Thursday, then reflected on the water taste change ahead.

While many cities, including Coeur d'Alene and Rathdrum, add small amounts of chlorine to their water systems year-round as a disinfectant to ensure safe drinking water, Post Falls chooses to chlorinate just one month each fall.

That process starts on Monday and will run for 30 continuous days, prompting Post Falls to send out an annual heads-up that their residents may notice an odor or different taste during the process.

Miller knows the drill.

Just like taxes, the Post Falls woman is reminded it's just something that has to be endured each year.

"I don't drink as much water during that time - just the minimum," she said. "I could always use a filter for my water or buy it, but haven't gotten around to it. It must not be a huge priority because I haven't taken those steps.

"For the most part, it's just one of those tough pills to swallow, but, if it's for your own good, you put up with it."

Other areas put up with it as well.

In fact, only a handful of cities in the region don't use chlorine in their systems as the method of choice to beat bacteria, according to the U.S. Environmental Protection Agency. Other ways to protect against bacteria - including ultraviolet light and ozone - provide disinfection at the point of treatment but disinfection does not remain effective in the distribution lines.

"Chlorination is the only method in which to accomplish this," said Suzanne Scheidt, drinking water program supervisor for the Idaho Department of Environmental Quality, which regulates the systems of area cities.

Time-tested treatment

City officials say chlorination is the best all-around insurance policy to making sure tap water stays safe. The process has been used by area cities for many years and there's no plans to change the time-tested approach.

"I've been here 20 years and it was used a long time before I got here," said Jim Markley, Coeur d'Alene's water superintendent. "Chlorination is the most common form of disinfection used by water systems in the United States."

However, chlorination is not required in Idaho as long as water providers meet water quality standards.

Even though chlorine - the same chemical that's in swimming pools - has been applied to tap water for years, the process still catches some residents by surprise.

"That's interesting - I didn't know they did that," said Deb Williams, a friend of Miller's from Post Falls. "I just hope there's more good that comes from doing it than bad."

Coeur d'Alene and Rathdrum chlorinate year-round, shooting for a concentration of about .2 parts per million. The maximum allowed is 4.0 parts per million.

It's not uncommon for cities elsewhere to have a concentration between 2 to 3 ppm - much higher than the levels of local cities', water officials say. But this region's drinking water source - the Rathdrum Prairie aquifer - provides cleaner water than surface water sources such as rivers and lakes so the treatment process here is less involved.

"The water is pretty pure coming out of the aquifer," said Kevin Jump, Rathdrum engineer. "We simply inject chlorine before it's sent out into the system. It doesn't get any simpler than that."

Different philosophies

Markley said Coeur d'Alene chooses to chlorinate year-round because it provides continual protection from bacteria.

"If you have anything that compromises water quality, you have a little residual to protect you," he said, adding that a water main break or fire hydrant usage are examples of how water can become contaminated.

Even though Coeur d'Alene continually chlorinates, the city still fields scattered complaints of the taste.

"We don't get a lot, but we get a few," Markley said, adding that most residents are used to any taste due to the year-round chlorination process.

Jump said Rathdrum gets two or three complaints a year.

To Post Falls residents, the taste/odor from chlorination may be more distinct because it's a change from the other 11 months out of the year. The concentration level during the month of chlorination is .1 to .6 ppm, according to the city.

"We get a few complaints, but people generally accept it," said Mike Neher, environmental manager.

In addition to filters, another way to get rid of the taste is to put water into a pitcher and let it sit for several hours or overnight, he said.

Neher said Post Falls elects to only chlorinate for a month because of the "super clean" water from the aquifer and the city wants to avoid the taste drawback as much as possible.

"It's just a difference in philosophy and we try to keep people happy," he said.

Neher said the water circulates faster during the summer months due to lawns being irrigated, so bacteria buildup is less likely at that time.

There have been cases where bacteria enters the system in Post Falls and the chlorination system has had to be turned on during other months until the water is tested safe.

All cities regulated by IDEQ are required to test multiple parts of their system monthly for chlorine levels, bacteria, disinfection byproducts and other possible concerns. They are also required to report when the chlorination process is turned on and off.

Pros and cons

According to the Centers for Disease Control, the advantages of chlorination are a reduction of most bacteria and diarrheal disease, protection against recontamination, ease-of-use and low cost.

"Chlorination provides an immediate - albeit in most cases precautionary - response to address microbial contamination which may occur in the distribution system," Scheidt said.

Drawbacks, in addition to taste/odor objections, are less effectiveness in turbid waters, "relatively low" protection against protozoa and potential long-term effects of chlorination byproducts, the CDC states.

"When chlorine mixes with naturally occurring organic matter, disinfection byproducts are formed which at high enough levels may pose a health risk," Scheidt said.

However, tests over the years reveal that the byproducts from chlorination aren't a concern in North Idaho.

"Results within our region are well below maximum contaminant levels established for these contaminants," Scheidt said.

Wendy Marshall, an EPA drinking water scientist, said her agency believes the pros of chlorination far outweigh the cons and that it's meant to prevent sickness and even death from bacteria buildup in water.

"I've gotten sick from giardia (small intestine infection), and it was a miserable experience for more than six weeks," she said. "We're a big proponent of treating water appropriately."

Peace of mind from taking precautionary steps, Marshall said, is something chlorination offers.

"You never know what's going to happen (with a water system), so cities want to make sure that it stays safe," she said.