Removing chlorine & chloramines from London brewing water

[chastuck]

After doing a great deal of research, including correspondence with Thames Water, I now think I'm at the stage to arrive at a near definitive answer regarding treating brewing water to remove chlorine and chloramines for my brews. I was pleased to find that people who keep aquariums are equally concerned about their water as we brewers are, and many answers to our treatment problems can be found on tropical fish forums! Comments would be welcome on my conclusions.

In spite of perceived wisdom and statements on these forums, it is not generally possible to remove chloramines from water with a standard under-sink carbon filter. They will remove most of the chlorine, but chloramines are bound with ammonia and are more difficult to remove. For a carbon filter to remove chloramines the water must run very, very slow and the carbon filter or carbon block would have to be very, very large. Even then, the filter would be quickly saturated with chloramines and actually put more chloramines back into the water passing through. Boiling will not remove chloramines either.

Does your water have chloramines? It is almost certain that it does. Thames Water explained to me that chlorine easily comes out of solution as water travels along their pipes, so they use chloramines to ensure the water remains pure at the tap after being treated with chlorine at the treatment works. You can find how much chlorine/chloramine is in your water by looking at the water report for your area from your supplier online. Thames Water label this as "Residual Disinfectant" and for my area the 10/04/2012 report shows the level is 0.42mg/L, the mean of 94 samples taken over 01/01/2011-31/12/2011. I've looked at Thames Water reports back to 1974 and also at reports the utilities have to send to the government water quality inspectorate, the latter of which comprise of many 1000's of samples instead of the 100 or so you see in online reports. These have shown me that the peak of Residual Disinfectant in Thames Water was 0.92mg/L. This is what Thames Water tells me about the water that comes out of my tap in SE London:

1. In the London area chloramine, rather than free chlorine, is used as the residual disinfectant because it is more persistent in the extensive distribution system that serves the capital. The use of chloramine as the residual disinfectant involves the addition of a small amount of ammonia to the chlorinated water just before it leaves the treatment works.
2. At most of our large treatment works in London, we use chloramines (a combined mixture of chlorine and ammonia) to disinfect water supplies. Chloramine is a longer-lasting disinfectant, which continues to protect against and eliminate pathogens, whilst water is in transit through London's very extensive and complex network of mains. Our practice is to produce a chloramine, which is composed almost entirely of monochloramine, as it is a more effective disinfectant. To achieve that, we aim for a chlorine-to-ammonia ratio of around 4:1. When taking measurements of residual disinfectant, we do not evaluate the composition of its individual components (chlorine, and the various chloramines), but instead record total residual level. The figures quoted above are for a total residual disinfectant, consisting almost wholly of monochloramine. (My italics).

So Thames definitely use Chloramine in the water at a rate of about 0.5mg/L, up to my observed figures of 0.92mg/L maximum. This leads me to conclude that carbon filters may be good for removing VOCs, silt, odours, etc., but are not much good in the London area if they are being used solely to remove chlorine/chloramine. Additionally, to all intents and purposes I can ignore any chlorine only element of my residual disinfectant and safely work on the basis of it all being chloramines.

This has thus led me to what is now my preferred option to remove the "Residual Disinfectant", which is to use metabisulphite salts. An article on water treatment in Jim's Beer Kit advises using Sodium Metabisulphite to remove chlorine. Much of Jim's Beer Kit article is derived from an original piece of research by A.J. deLange and unfortunately mistypes and misinterprets some of it. Importantly, it leaves out entirely the use of Potassium Metabisulphite as a preferred option to Sodium Metabisulphite. I know PotMet is harder to obtain in this country, but online searching of brewery shops shows several that sell it. I prefer to use potassium metabisulphite as the sodium content of my water is already moderately high at a mean of 45.4 and peak of 159.9 mg/L. More sodium is not what I need!

My total liquor requirement for brewing is usually 50 litres and I end up with 32 litres for bottling or kegging. For the purposes of ease of the maths I round up the worst possible case of chloramines in my SE London tap water to be 1.0mg/L. Using the table in deLange's original article, rather than the abridged one in Jim's Beer Kit, shows me that my total PotMet salts requirement is 50L x 1mg x 3.127 per mg of monochloramine. Thus I need to add 156.35mg (0.156g) of potassium metabisulphite powder to "neutralise" my chloramine content in the 50 litres of brewing water. Arising from this treatment, and again using deLange's table, this will add 1.10mg/L of potassium, 2.70mg/L of sulphate, 0.51mg/L of ammonia, 1.0mg/L of chloride and my alkalinity will decrease by 1.43 ppm as CaCO3. Any excess of sulphur dioxide arising from overtreatment is of no concern as this mostly boils away or acts as a useful antioxidant.

Of course, removing chlorine/chloramines is not enough to make my water suitable for brewing. I paid for a Murphy & Son water analysis and their recommendations for my water for bitters and pale ales are to add AMS at the rate of 1.05mL per litre of total brewing water and DWB at the rate of 0.52g per litre of final beer to be made. AMS is added to the total liquor after the potassium metabisulphite has done its bit and DWB powder is mixed in with the dry mash grains. I would be happy to supply a table of the final position of my brewing liquor after all the salt additions to anyone that's interested. Needless to say, since following the above regimes the flavour and yeast activity of my beer has improved noticeably.

[Graham]

Aw Gawd, just 23 posts, and suddenly someone is preaching an awful lot pseudo-scientific gobbledegook. It is not as if most people on here are not aware of their water quality or what they need to do to improve it.

[Jim]

While water treatment and chlorine/chloramine removal can be important (depending on your water supply) it's easy to worry about it too much. As long as you get the majority of it out, you'll not notice anything untoward in the final beer.

I personally would advise looking at other aspects of brewing before going to the far end of it on water treatment, as you'll have more impact on the quality of the beer that way. You can still make crap beer even with perfect water!

[chastuck]

Aw Gawd, just 23 posts, and suddenly someone is preaching an awful lot pseudo-scientific gobbledegook. It is not as if most people on here are not aware of their water quality or what they need to do to improve it.

I really would appreciate knowing which part of my message is "gobbledegook". And the number of posts does not limit the right to add to the wide base of knowledge here. There are many people on this site with various backgrounds in scientific knowledge and surely the point of it all is to share information, regardless of personal criticism. I know your own knowledge is very worthy and if you are who I think you are from your initials I have followed your advice in the past very earnestly. But you don't know it all! I started my working life in a brewery and have been grain brewing for over 40 years. Anything you can add to improve or clarify what I put up would be truly welcome.

[chastuck]

While water treatment and chlorine/chloramine removal can be important (depending on your water supply) it's easy to worry about it too much. As long as you get the majority of it out, you'll not notice anything untoward in the final beer.

I personally would advise looking at other aspects of brewing before going to the far end of it on water treatment, as you'll have more impact on the quality of the beer that way. You can still make crap beer even with perfect water!

A very wise and true comment. All I'm trying to do is to help other home brewers in their search for knowledge on water treatment. The quality and of Thames Water in my area has been up and down in recent years so I hope I've added to the general pool of information.