Homebrew

WezV

Yeah, I have used campden tablets. not sure adding sulphites is comparable to starting with water that has less additives in the first place.

obviously it depends on the quality of your tap water, and that varies massively across the UK.  I live in Burton where the best brewing water is, but that isn't what comes out the taps and work don't let me take directly from the aquifers.

oaf

Don't think of it as what the tablet adds:
http://www.jimsbeerkit.co.uk/water_chlorine.htm

The article above suggests 1/2 tablet per 10 gallons but I haven't had issues with 1/2 per 5-6. It's a YMMV thing and will depend on your water.