Diluting wort. Tap water? or Boiled water?

[phatboytall]

I often boil 35l of high gravity wort which I then dilute down to make two 4% 23litre brews. Obviously hop isomersation is a factor, but i've never found it makes much difference, anyway thats a different topic.

When diluting boiled wort do you have to use boiled water?

Or is fresh tap water sterile enough to add?

[Jocky]

Most kit brewers use tap water without too much of an issue, but I think it's one of those things that you can do without a problem most of the time, but it doesn't exactly stack the deck in your favour when it comes to avoiding problems.

[mabrungard]

There are 2 issues. Disinfectant removal from tap water and oxygen removal.

There are several options for disinfectant removal. Something should be done to whatever water is used since chlorophenols in beer are perceptible at very low concentrations. The issue with oxygen in water has to do with the reduction in shelf life due to premature staling. In essence, the oxygen will increase the oxidation of the beer. If you are not storing these beers long, then this is not really an issue, but it is a big deal for beers you will be storing.

[legion]

I do a similar setup with my brews and use bottle water when topping up. but tap water should be find with an appropiate amount of campden tablet.

The yeast will want oxygen in the tap water

[gregorach]

The issue with oxygen in water has to do with the reduction in shelf life due to premature staling. In essence, the oxygen will increase the oxidation of the beer. If you are not storing these beers long, then this is not really an issue, but it is a big deal for beers you will be storing.

Depends on whether this is before or after fermentation... The OP implies that it's before.

[critch]

chlorophenol and chloroamines wont be a problem with boiled water as they flash off at 50.c+ temps

[mabrungard]

Depends on whether this is before or after fermentation... The OP implies that it's before.

Good point, I didn't see that. The oxygen reduction is for post-fermentation use. Many large commercial brewers use high gravity brewing to increase the throughput in their fermenters. Diluting the beer to sales gravity following that ferment would require low oxygen water.