Campden Tablets & Water Prep.?

[DDoe]

Very basic question I think, but just want to clarify.

I shall be starting my first extract brew this week. I'm planning to to add a Campden tablet to the brewing water to get rid of the chlorine, but have a couple of questions

1) I'm making a 5L batch so will prepare 10L of water, as my tub of C.tabs has 1 tablet upto 25L should I use just half a tablet.

2) should I cover the bucket of water+C.tab. when leaving it overnight or leave it open.

Thank you for any help.

[guypettigrew]

If you're brewing an extract beer then chlorine shouldn't really be a problem.

Best bet is to run your 10L into the bucket the day before and leave it open until the next day. Should get rid of any chlorine.

Guy

[f00b4r]

Just use half a tablet but you do not need to leave it overnight to react. I tend to just crush a tablet between two teaspoons and then stir into the water. I believe the reaction is very quick (someone correct me if I am wrong), so you can just do whilst prepping everything.
Whether it is needed is debatable (it depends on your water supplier and how they treat your water), but I have always used one out of a belt and braces approach and not wanting to risk a batch; others have found it unnecessary after forgetting to use at some point and not getting issues.

[DDoe]

Thanks guys.

[Silver_Is_Money]

For a vast majority of cases 1/4 tablet is likely to be plenty for 20-25L.

[DDoe]

Will it do any harm if too much is used?

[Silver_Is_Money]

Will it do any harm if too much is used?

It somewhat raises your mg/L (ppm) of SO4-- ions. Each ppm of "oxidized" Sodium Metabisulfite has the potential to produce ~1 ppm of SO4. Each ppm of "oxidized" Potassium Metabisulfite has the potential to produce ~0.86 ppm of SO4. How much of the excess Metabisulfite gets "oxidized" is the question that must be answered whereby to determine how much of an SO4 increase will occur.

Additional SO4 is not likely to be outright harmful. Much depends upon whether additional SO4 is desired or not for the style being brewed.