Does "make-up" water added at the boil stage need to be treated?

I do BIAB and often push the volume limits on my 10-gal pot.  If I want to add water after the mashed grain has been pulled from the pot before I start the boil phase does it need to be treated like the mash water was?

Thanks in advance for your advice.

Not necessary when adding a reasonable amount of water post mash. You can add Sulfate, Chloride and Sodium to season the beer at any time, right up until packaging, as you would salt and pepper to your food.

Bob is correct. There are two reasons to add salts to mash water: 1) to get correct pH during mashing for efficient conversion, and 2) to get the proper balance for final flavor. Any water added after the mash only needs seasoning for final flavor. That may be a different treatment than the mash water got.

As long as you’re adding ‘make up’ water, may I recommend you pour it over your grain bed to get any additional sugars you may have left behind?

I only use brewing salts in the mash for pH. All other additions for flavor profile go in the kettle targeting post boil volume.

In my opinion, it doesn’t matter what volume you start with pre boil. The flavor profile for is post boil volume up to and including by-the-glass.

Thanks for the suggestion regarding pouring the make-up water over the grains although that idea had already occurred to me.

The mineral content of the makeup water doesn’t have to be adjusted, but it might be a good idea.  The ‘have to’ items to adjust for your makeup water is chlorine removal and alkalinity adjustment.  If you’re using distilled or RO water, you won’t need to worry about the ‘have to’ items since they’re already taken care of.

Thanks, Martin.

I rely on your spreadsheet for water treatment and with the yeast it helps me brew liquid magic.