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Comment by mchannon | Hacker News Reader

This article's full of problems.

The first reason chloramine gets to be a problem is users don't shower before entering the pool. The amount of urine a swimmer can introduce into the water is small compared to the amount of urea coming off their unwashed body. Icelandic people religiously shower before entering their shared baths, and look on non-showering the way we might look at people not bothering to wiping their backside.

And the other two big misconceptions are that time will take care of the problem (chlorine evaporates, amines don't) and that you can just dump in chlorine or other chemicals to get rid of the problem. It uses far less energy and wastes less water to simply dump and replace the pool water (chlorine tablets require ridiculous amounts of water and energy in their manufacture).

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Pool shock (a spike in active chlorine) will react with amines and oxidise them -- saying they don't work is bizarre. It is painful to do manually though. A UV filtration system is far easier, but also far more expensive.

Dumping water isn't practical as many places have water restrictions. Chlorine gas is produced in vast quantities industrially, then compounds like calcium chloride, sodium hypochlorite and sodium dichloroisocyanurate, which are used in both fresh water and waste water treatment. So when you dump your pool water you are still using chlorination, just at the municipal level.

"saying they don't work is bizarre"- that it doesn't work is pretty much exactly what the article says, and it's true, as long as "work" is defined as not turning your eyes red.

Shock is useful for raising the total chlorine concentration in the pool, which is useful for discouraging bacteria, but it'll boil off in a day. If you have more amines to tie up chlorine than you add chlorine, bacteria and algae grow because the shock doesn't become "free chlorine".

UV light removes chlorine from the pool, but similarly does little to remove amines.

Dumping the water in a pool uses an equivalent amount of water to watering a similarly sized lawn over the course of as little as a few months. It's not free, but it distorts the overall scale of usage to bring up water restrictions.

A fresh fill of pool water has no amines in it, and consumes very little chlorine at the municipal level (which boils off quickly). Just because something is "produced in vast quantities industrially" doesn't make it cheaper than water. It's not. Hypochlorite tablets and shock are, like aluminum, essentially solid electricity.

Do people actually water lawns outside of Hollywood and golf courses?

Yes

In semi-arid southern Australia, even with a native (low-rainfall) grass, the "lawns" need help through the summer. In the cities I've no idea of the split between native grasses and thirsty "decorative" grasses - but both are common.

The article is not saying chlorine doesn't work... It's saying don't poo in the pool.

The shock is not primarily to kill bacteria, but to deal with the amines. It is designed to disperse, because the concentration of chlorine would be far too high for people -- usually 10x the normal level of free chlorine. If you went into a pool with so much contamination (ammonia products or slime) that pool shock wouldn't work, you'd be getting very sick.

UV does not remove chlorine (chlorine ions are elemental), but it does break down amines and kill pathogens. How it works is complicated: 259983997_Effects_of_Combined_UV_and_Chlorine_Treatment_on_the_Formation_of_Trichloronitromethane_from_Amine_Precursors

Many areas with water restrictions ban dumping and refilling pools, which would in many cases would incur a cost of thousands of dollars, vs $30 for a bucket of shock.

"The amount of urine a swimmer can introduce into the water is small compared to the amount of urea coming off their unwashed body" - really? how much urea does a normal human have on their body, assumed they wash at all e.g. if they showered this morning, and go to pool after work ? Assuming they don't spend the day pissing on themselves, do we just secrete urea?

Yes, we do (a little bit).

Uric acid and urea in human sweat: https://www.ncbi.nlm.nih.gov/pubmed/12817713

Also remember the number of people getting in the pool is likely much larger then the number of people peeing in it.

That's weird, because the only reason to go to a public pool is so you could pee in it.

The article does mention several times that people should shower before using the pool, in addition to not urinating in the water.

>users Tee-hee

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