It will if it's reverse osmosis (RO), but not all filters do that. That particular brand sells both RO and non-RO units. If it's a vast excess of NaOH, you'll have other problems besides your water filter failing, like chemical burns.

Most US tapwater is fantastically clean and drinkable, and doesn't generally need a filter. The Safe Drinking Water Act is pretty powerful stuff.

https://www.cdc.gov/healthywater/drinking/public/regulations...

US tap water is generally so high in chlorine that to people from Western Europe it smells like pool water, even in places that are proud of their tap water like NYC. Having lived here for ten years now I can no longer smell it when I turn on the sink, but visitors still can.

I live in Seattle, WA, which apparently has some of the cleanest water in the country.

I use one of those under-the-sink inline charcoal cartridge filters on the sink we use to make tea or cook with. If I grab some water from a different tap, you can tell immediately by the smell (chlorine) and the taste.

I'm surprised the filter takes out the chlorine honestly, but it's clearly taking out a bunch of stuff from what is otherwise considered very clean.

That said, having travelled extensively through places like India, South America, East Asia, etc., I'm certainly grateful for the water we have "on tap" in the house. It's easy to take for granted.

You can blame the EPA for mandating chlorination in Seattle's water supply. The watersheds that feed into Seattle drinking water are "Surface Water" and considered high risk by the EPA. This risk assessment is probably more accurate in the rest of the country; our protected watersheds are fairly uncommon. But we don't get any special exemption.

EPA mandates a floor of 0.2 mg/L chlorine for all Surface Water based drinking water supplies at all times[0]. There are additional chlorine requirements depending on what sort of filtration you perform, if any, and how far the first service connection is from the chlorine insertion, in minutes. (They also mandate a safety ceiling of 4 mg/L for all drinking water.) This level is continuously monitored.

Seattle does about 1 mg/L to meet these EPA-imposed requirements.[1]

Chlorine evaporates out of water, so if you don't like the taste, you can just let tap water sit a while. Sunlight helps. Boiling water (e.g., for tea) also removes most of the chlorine.

[0]: (PDF) https://www.epa.gov/dwreginfo/swtr-plain-english-guide

[1]: (PDF, p. 8) https://www.seattle.gov/Documents/Departments/SPU/Services/W...

Weird. Here in Germany we have some protected watershed areas on smaller rivers that directly feed a surface reservoir, created in the river valley through a dam.

They get filtered, but there is no chlorine directly. Some chlorine dioxide is used at the end, though. Here's the official description of the utility, translated to english:

- Via a raw water pumping station, the dam water first reaches the micro-screening plant. It removes coarse contaminants over 35 ~ µm in diameter through stainless steel mesh filters. This provides special safety in times of mass algae growth or during floods.

- Subsequently, the raw water is de-stabilized with a flocculant; and turbid matter accumulates to form large flocs.

- In filter stage 1, two filter materials of different coarseness are used to remove the flocs.

- Ozone is then added to disinfect the raw water.

- Filter stage 2 is equipped with activated carbon and frees the raw water from the reaction products of ozonation. Excess ozone reacts to form oxygen and is thus removed from the raw water.

- The further filter stage 3 uses natural limestone material over which the water flows. Here the excess carbonic acid in the water is removed. Finally, a small protective disinfection with chlorine dioxide takes place before the drinking water leaves the clean water tank in the direction of <city>.

The steps are similar in Seattle, although I think we filter less. I'm having a hard time finding a concise but also technical description of water treatment steps. We definitely do:

- Ozone disinfection, and removal

- Tolt river supply only: water conditioning by filtering through "granular media." (Cedar river supply is clear enough without this step.)

- UV disinfection

- pH adjustment to avoid corroding pipes

- Flouridation for public health

- Chlorination as a final step as water leaves the treatment plant, and also at some downstream facilities (like a networking repeater; just to maintain chlorine levels that would otherwise have fallen due to distance from the upstream chlorination site)

Tolt: http://www.seattle.gov/utilities/your-services/water/water-s...

Cedar: http://www.seattle.gov/utilities/your-services/water/water-s...

Small tidbit, ascorbic acid kills chlorine and chloroamine.

You can also just let the water sit and the chlorine will evaporate out.

True with Chlorine, chloroamine not as much.

Sure; I did not say otherwise. Seattle (where OP lives) does not use chloramine.

> You might hear about different forms of chlorine. Seattle's water system uses "free chlorine" (not chloramines).

http://www.seattle.gov/utilities/your-services/water/water-s...

Is there a health risk to consuming chlorine in water?

I had some tap water in Scotland about 20 years ago and I still remember how amazing it tasted. This was in Aberdeen area if that makes a difference. It was like the finest artesian spring water I’ve ever had.

I remember being able to taste the chlorine through the soda machine in Phoenix.

Yup. Thats one of the things I remember most vividly from my trip to NY as a kid in the 90s.

> Most US tapwater is fantastically clean and drinkable, and doesn't generally need a filter.

It is my understanding that most municipal water utilities only test water quality every 3 months. A problem can come and go between testing cycles.

Even with weekly testing, I’d expect the same risk (there’s still a window between tests). Basically you’re only going to know about a problem when it’s too late.

Your understanding is incorrect.

It depends on what contaminant you are measuring, but the testing frequency can vary from "every several years" to "continuously monitored and sets off a SCADA alarm if it exceeds a given threshold." The biggies--IIRC, turbidity, pH, and dosages of coagulant and treatment chemicals--are logged every 15 minutes, with more tests happening on hourly 6-hourly, and daily frequencies, followed by yet more contaminants happening largely on monthly or quarterly assessment bases. The issue in question would have shown up in a pH measurement, so there's no reason it shouldn't have been caught within minutes.

You also have to look at the success and failure rates of those tests. Most tests reveal no problems, which implies periodic sampling is plenty to handle the rare problems that crop up. If we found more problems, we would demand more testing, but increased testing is pointless if there is no problem to be found. In reverse, if the tests are not specific enough, they can cause issues when you over test due to false positives on the tests.

Indeed, you'll see that if a water test comes back positive, there will be multiple retests and a much greater rate of testing until the problem is abated, at least at my local drinking water board.

> It is my understanding that most municipal water utilities only test water quality every 3 months. A problem can come and go between testing cycles.

This isn't remotely true.

Which part?

The whole of it. You stated that most municipal water supplies aren't monitored for months at a time. This is extremely incorrect. The EPA-mandated quarterly report is a summary, not the entirety of samples collected. It would be dangerous and reckless not to monitor drinking water for months at a time.

E.g., Seattle explicitly states:

> We monitor your water 24 hours a day, 365 days a year. We test samples from the region between 10 and 100 times per day.

https://www.seattle.gov/Documents/Departments/SPU/Services/W... (PDF)

> To ensure the safety of our drinking water, SPU's water quality laboratory analyzes over 20,000 microbiological samples each year (more than 50 a day) and conducts chemical and physical monitoring daily, 365 days per year.

https://www.seattle.gov/utilities/your-services/water/water-...