How long does K metabisulfite take to dechlorinate tap water?

How quick is this reaction. I was advised to give it 24 hours by one of the NB brewmasters a while back, but I’m starting to question this. Looking at the chemistry, I’m not sure why this reaction would take that long. Does anyone have a solid source to answer this question? The Water Knowledge page at Brun’ Water does not have this answer. Thank you.

I’m pretty sure that @mabrungard has said in the past that the reaction is pretty much instantaneous. Hopefully he’ll drop by to clarify!

*full disclosure, I don’t have chloramine in my water so haven’t used Campden for this purpose.

Yeah, not more than a few seconds.

Awesome. Thanks, guys!