I usually need to collect 6.5 gallons of wort. Once the specific gravity gets to the point that can no longer collect due to the risk of tannis is it best to top off with water before the boil, or after the boil?
I did this just today. What I did was wait for my hot break then add my water immediately after. I do it this way because, at least for the beers I’ve been brewing lately, I get about 8 inches of foam at the hot break, which lasts about 1 minute, then dies down to nothing.
As I mentioned in another thread, I think that gypsum contributes to a huge hot break.
Anyway, waiting before making up the water gives me an inch or so and helps that much to prevent boilovers.
FWIW, I don’t worry that much about extracting tannins. I just try to sparge slowly and just collect until I get the volume I want. I’ve stopped checking the gravity of the final runnings. Oh, and I do decoctions sometimes, which you would think would be a major source of tannins. Meh.
Thanks for the advice!!