Chloramine boils off in 5- 20 minutes according to my water company
 

It does boil off, just takes longer. SF water works says it takes 20 minutes in their city water.

No, that's not so. It's more like hours and hours, just to get to a half-life. In practical terms, chloramines do not boil off. Chlorine does, if the entire amount of water is boiled and the brew is not topped off with unboiled water.

The easy way to deal with chlorine is to just put the brewing water out overnight and let the chlorine dissipate and forget boiling it.

For chloramines, adding 1 campden tablet to 20 gallons of water will cause the chloramine to dissipate.

Do you have a source for this information that is not the sketchy document hosted on hbd.org?

The SF waterwork website says it takes twenty minutes to boil chloramine off.

Going to add now http://www.phila.gov/water/fact_sheets.html

Says it takes 5 minutes of boiling to remove half of chloramine:

Does boiling improve the taste of tap water? It is unlikely that you will notice any taste difference. The primary reason for the taste of tap water is the chloramine (chlorine) that is in the water. This gives the water a slight chlorine taste. The chloramine is there to maintain the freshness of the water throughout the City. Chloramine is used because it is persistent. Boiling water for five minutes might only reduce the chloramine level by half. It will not get rid of the chloramine. Placing the water in the refrigerator in a water jug will help to reduce the chlorine taste since colder water has a less noticeable taste.

http://www.chloramine.org/chloraminefacts.htm

Read up here a bit.

It's not as easy as you think. It will break down into bi products, and still be intact.

Placing it in the fridge, might "hide" the taste. Similar to the fact that a colder beer, will mask the fact that it has a bad taste. Look at a BMC beer. Drink that at cask/cellar temp, v. a craft or home brew and let me know which taste better. Your "quote" even says that it's only at it's half life. Which means it's not gone, which can still produce an off flavor!

Chloramine isn't chlorine. It's a combo of ammonia AND chlorine that are bonded. You can beat the chlorine chain, but are left with the still nasty ammonia side of the chain.

Chloramine is used because people will think they don't have the smell or taste of chlorine, but it's there. It's hidden much better. It's "persistent' as your quote says.. More so than you are leading to believe.

Boiling it longer does little to nothing. You can super chlorinate it, which is impractical in brewing. Or you can use a campden tablet, or a really large amount of carbon to reduce it. UV is the best way to handle it, and that can be done from getting water from places like the Glacier water machines that use RO and UV to clean the water. People that use their tap to top up their saltwater aquariums will use UV and RO exclusively, to avoid any issues. These people aren't boiling their water to use it.

I know what chloramine is my friend. I just want to know what document says it takes more than 20 minutes of boiling water to get rid of most of it. And there are none except that old document from the 90's hosted on that beer website that is not even well written. Why not well written? Because it doesn't say "hours and hours" of boiling. It just says "longer" (then chlorine). Like ... in seconds maybe?

It doesn't matter what that document says. It's dated.

There are many AUTHORITATIVE places that claim it takes minutes of boiling to get rid of chloramine.

And your 'half-life'... meaning half of it can be removed: 5 minutes.

Chlorine evaporates completely before water reaches boiling point. It's quite unstable.

This is something THIS website in particular is going to have to dispell as a bad bit of information that has gone on way too long. Not that most people will want to boil their water for 20 minutes anyway but ... really let's stop this madness.

Ok everyone calm down... This web page should shed light on some of this...
http://hbd.org/ajdelange/Brewing_articles/BT_Chlorine.pdf
It states that the half life is somewhere around 26.6 mins but it would have to undergo many half lives to be completely removed... So if you do two half lives then there's still 1/4th of the chloramine in it. So to completely remove it then yes it would take hours

Yes, I'm incredibly familiar with the half-life concept, as medications involve calculating half lifes.

The thing with removing chloramine is that you don't want HALF of it, or a quarter of it, or an eight of it, or any bit of it left. It has a very low taste threshold in beer. It would take hours and hours to remove enough to not impact the flavor.

OR. You can add a crushed campden tablet (potassium metabisulfate) to 20 gallons of water, stir it. And it will interact with the chloramine and give you usable water in moments.

Anyway, one of the signs of chlorine or chloramine in brewing water is a burnt-cloves kind of flavor, like band-aids would taste if you tasted them.

Do you need to adjust the campden amount for less water? Say a 5 gallon batch. Guess I should say 7 gallons or so to start.

Yes. Cut the tablet in half, or quarter, or whatever for your volume.