Only tests can show how effectively the product removes chlorine. However, the principle (reducing an oxidant, such as chlorine, with a zinc-copper couple) is well known.

But why bother? When you take a shower, do you experience any bad effects that you attribute to chlorine? You are exposed to far more chlorine when you swim in a chlorinated pool.

The best scientific reference that the manufacturers can find, provides no evidence that chlorine is harmful at these levels. It is not a cumulative poison. If you are OK after 10 days exposure you should be OK after 10 years.

I'd be more worried about the water you drink. If there are organic compounds in the water, chlorine can react with them to produce carcinogens. It is hard to quantify the risk, but a lot of people use an active carbon filter to remove such compounds from their drinking water.

Most important of all, in some areas it is essential to filter the tapwater, to make a decent cup of tea.

Why do you want to remove free chlorine?
If it were a swimming pool you would usually be trying to add/maintain it.
Personally I would consider it pretty harmless (though some of it's reaction products are less harmless - but how likely are you to have significant amounts of them?)

If I wanted rid of it from a large volume of cold water I would probably use an activated carbon filter. Or UV.
But it depends how much you have, how much you need to reduce it by, and what your flow rates at treatment are.
A carbon filter needs maintenance/replacement regularly depending on use too.

Why the shower water particularly? It's not like you drink it anyway.
Do you use laundry agents that contain bleach? They would expose you to much higher levels.

Posted By: rhamduIt is not a cumulative poison.

Posted By: VictorianecoOf course it is a cumulative poison,

So, diametrically opposed points of view.

Do either of you care to post refereed, published references to back up your assertions?

My naive understanding of water board policy is that they put enough chlorine in to sterilise the public mains and that if you can still detect a noticeable amount at the point of delivery they will investigate the fault when reported. Am I wrong and/or is the policy insufficient?

What is the risk, having removed chlorine from the shower water, that water standing within the shower head could be a breeding ground for legionella?

http://www.all4women.co.za/health/health-articles/drinking-water-purifiers-the-hidden-dangers

"Dangers of removing chlorine from drinking water

However, chlorine has been added to water for a purpose; to protect your health from dangerous bacteria which cannot breed in chlorinated water! By removing the chlorine, you can re-create a situation in which these dangerous bacteria can breed freely, and this is what some (not all) water purifiers do.

Durban Municipal water experts have been quoted as saying that some water purifiers become breeding grounds for bacteria with the unintended result that clean tap water is turned into water that is not even fit for recreational purposes.

The municipality is suffiently concerned that it has appealed to residents with water purifying systems to allow the municipality to test the filtered water they are drinking.

According to Neil Macleod, Head of Water and Sanitation, eThekwini Municipality, some home water purifying systems use activated carbon as the filtering mechanism. The concern here is that such filters do remove chlorine but they can also lead to an explosion in the growth of bacteria.

They have been similar warnings from the US State of Minnesota, where the Department of Health has warned against assuming that home filtered water is better than unfiltered water.

We asked Neil Macleod if the problem lies in the Carbon filter or in the water sitting around after de-chlorination:

"Any water filter that removes the disinfecting agent (which is chlorine in most cities in the world) exposes the users to risk of bacterial infection, unless the water temperature is very cold - say less that 6 degrees centigrade - and the bacteria are not viable. Carbon filters not only remove the chlorine but also provide food and ideal places for the bacteria to grow!"

I just wanted to 2nd what Cwatters said. Personally I would definitely prefer to have the Chlorine than not.
We also keep plain ordinary bleach around (that's all the chlorine in water is after all) and I would not be without it for very occasional sensible use but that use probably exposes us to much more free chlorine than showering does.

Our tap-water is less than 0.5 ppm (ie. 0.5 mg/litre) fresh from the tap. That quickly dissipates if you heat the water or leave it to stand for bit.

Swimming pools are interesting. That industry has a lot of quackery and snake-oil water treatments. There is little I would trust apart from Chlorine for that job. You need some residual disinfection in the water so Ozone or UV alone won't do it... and Ozone and UV both remove your free chlorine so if you combine them you have to be careful. You should see what grows in pool filters (where UV and Ozone can't reach) given half a chance.

Posted By: SprocketSwimming pools are interesting. That industry has a lot of quackery and snake-oil water treatments. There is little I would trust apart from Chlorine for that job. You need some residual disinfection in the water so Ozone or UV alone won't do it... and Ozone and UV both remove your free chlorine so if you combine them you have to be careful. You should see what grows in pool filters (where UV and Ozone can't reach) given half a chance.

Speaking of pools, I recall now that if we have any money when we've finished the house we've been considering building a natural pool, which takes a few tips from nature on filtration and uses plants and animals to keep the water clean:
http://www.youtube.com/watch?v=LpZ9s7RpAr0

I've lasted over 50 years only drinking corporation pop!

Triassic I'm sure drinking chlorinated water won't kill you long term but it is proven that chlorine affects thyroid function.

For somebody who is hypothyroid like myself any small changes I can make I do...

> chlorine affects thyroid function.

Hi Victorineco,

Iodine (either form salt or from other things in your environment) obviously can directly affect thyroid function. I have heard but not seen proof that Bromine (as Bromide) can too.

I would have thought that further suspect would be chloride rather than chlorine directly (and also rather than OCl/HOCl ions as you would get from Chlorine in water). Even if free chlorine is reduced to chloride by it's environment there would still be insignificant amount of the chloride from this rather than e.g.. from salt in your diet so chlorine in water seems unlikely to be an issue.

Have you got a reference for that kind of thing with chlorine? I found this (which says no effect) but it's not exactly a big sample size).

I http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1567021/

Posted By: Sprocketalso interesting to note that no-one has gone anywhere near ST's comment!

Probably best in these politically correct times or we will all be dropping back into 1970s language.