Boiling will work for chlorine, but may not drive chloramine off. It will also precipitate out calcium carbonate, which reduces the hardness of the water, but can also result in a Calcium ion deficient water.
I now dechlorinate my water with a pinch of sodium metabisulphite, or half a campden tablet, for each 15 litres. As soon as I started to treat the chlorine in my water this way, a consistent problem I was having with polyphenolic astringency went away and my beers became a lot cleaner in flavour.
Any residual sodium met after the dechlorination process will be beneficial in the mash, as it will work to prevent oxidation.
Sodium met isn't for everyone. Its fairly nasty stuff, and known to trigger asthma attacks and skin allergies (eczema, urticaria) in some people.
My own water treatment regime was worked out using Ken Schwartz's BreWater 3.0
For Brisbane water it consists of:
- dechlorinate with sodium metabisulphite. This tends to bring the pH down from 7.9 to about 7.1, due to production of sulphurous acid as one of the side effects of the chlorine neutralisation reaction.
- Boost calcium to 50ppm by adding about 1g of either Calcium Sulphate or Calcium Chloride to each 10 litres of water. Necessary because Brisbane water has low Calcium levels (< 20 ppm)
- For English styles I go further with 2g Calcium Sulphate and 0.25g Magnesium Sulphate per 10 litres of water. This gives a much crisper pale ale or bitter without going over the top with full Burtonisation.
- pH of sparge water is adjusted to around 5.5, which takes about 2 ml of 85% phosphoric acid per 10 litres.
This regime, for Brisbane Water, has given consistently good beers, mash pH in the right ballpark (around 5.3), and minimal tannin extraction even when I have sparged below 1.010.
You will need to work out what works for your own local water profile. One man's water treatment won't work for someone with different water. It is therefore important to start simple, and only make changes if you feel you need to (like I did due to my chlorine driven off flavours).