How much salts for treatment?

Water treatment charts usually list amounts "for 5 gallons." I end up with a 5 gallon batch, but have 9 gallons of water in the boiler at the start of the boil. Do I use the salts amounts from the 5 gallon chart or increase proportionately (X 1.8) for the 9-gal in the boiler at the start? Thanks

A proportional increase should work just fine. Just be sure you're starting with a known water chemistry before adding salts.

Thanks. My concern was that after the water boiled down to 5 gal, it could be over-salted if I treated with a dose for 9 gal.

Like Yuri I stress that you know for sure your water makeup. Are you trying for an identical style?
In my experience, limited as it is, I have found that this is almost impossible as my water changes season to season slightly, and keeping up with an excact profile is contrary to my lazy approach. Now I just keep the PH in line and add slight amounts to the boil to get my desired effect.

BTW you collect 9 gallons to boil down to 5 gallons? That is a lot of boiling.

We have flat-out soft water for starters. I have a 12-gal boiler over gas flame that will go from 9-gal to 5.5 (incl the fallout) in 90 minutes of even rolling boil. Here we can brew most anything with a bit of gypsum or CaCl for the mash and sparge (or some chalk in the mash & boil for high-acid grain mixes lke a doppelbock), but aiming for the likes of London water etc adds to the fun for me.
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