I keep getting a sort of bitter taste with most of my brews and I'm just not sure what it is, so I thought maybe a bigger brew may be the answer.
I mash/brew in a 19ltr SS kettle for a usual 10ltr brew of a basic APA or a Dr Smurto DSJA but I would now like to go bigger to say a 15 ltr brew.
I have read that a 15ltr brew is possible in a 19ltr kettle by doing a mash of say 16 ltr then while that is mashing heat up another 3 ltrs in another pot for a 10 mins rinse/sparge then using that to top up the kettle to the max of 16 ltr for the boil, ( 16 ltr is the limit I set so i can safely boil without boil over )
As I would still be loosing another 4 ltrs or so on the boil when is the right time to add more top up water?
1. Should it be during the boil process (adding Boiling water during the Boil)
2. Should it be after Boil? (adding Boiled water to top up to 16 ltrs allowing for trub)
3. Should it be topped up to 15 ltrs in the fermenter prior to adding yeast

Also is this method a recommended/proper procedure for a bigger brew and will my readings be affected in anyway during the process?..... or has anyone got any ideas I should check for regarding the bitterish taste