Potassium Metabisulphite powder

[95bearcat]

I wanted to use potassium metabisulphite powder for chloramine/chlorine removal and was wondering if anyone else has used and how much to use? They say that Campden tablets crushed are about 1/4 tsp which treats abouts 20 gallons. I am not sure as I have not been able to find exact info on just the powder, but I would assume it be about the same concentration?

Any help would be appreciated.

[Travisty]

In home winemaking they usually equate 1 campden tablet per gallon to 1/4 tsp of k-meta per 6 gallons. That means that 1 campden tablet is equal to 1/24 tsp of the powder. It would be a little hard to measure that small amount. However, having a little bit of excess sulfites to treat chlorine/chloramine won't really be an issue. I would say that if you need to use the powder you could eyeball a half of an 1/8 tsp to treat 20 gallons. The tablets are real cheap though.

[JohnF]

The tablets I have weigh about 0.45 gram, IIRC.

The one tablet per 20 gallons is based on relatively accessible chemistry and the assumption that the water has the maximum chlorine allowable in the US. This all comes from a paper written by AJ Delange and available on his website. You can search for posts he has made here about metabisulphite for more info.

[ajdelange]

One can calculate exactly how much metabite is needed but to do so requires knowledge of the amounts of chlorine and chloramine. Of course you can let the chlorine go off by heating or standing (before metabite treatment) and just treat the chloramine. But for a precise calculation you'd still need to know how much chloramine. The reaction is very fast and your nose is a pretty good detector so you can, especially with the powder add a smidgeon, stir and sniff. If you smell sulfur dioxide you over did it. Use less next time. If you still smell chlorine, you need a bit more. Go for slight SO2 odor. As noted, a little extra won't hurt you a bit.

[95bearcat]

Thank you for the info.

[dstar26t]

Having never used the tablets, I saw somewhere that one tablet is .44 grams so I use .02 grams (.44gm/20gal) per gallon of the powder.