[Ian]

Help! I read in Gordon Strong's 'Modern Homebrew Techniques' that he adds "about 1/4 tsp of 10% phosphoric acid per 5 gallons of RO water to achieve a pH of 5.5 at room temperature" ...... "to reach a good mash pH of about 5.1 to 5.3 (with a pale grist)". However, my recipe software - Brewer's Friend - indicates I need substantially more 10% phosphoric to achieve the same effect, more like 1/2 tsp per gallon! Am I misunderstanding something or making a mistake?

[erockrph]

Help! I read in Gordon Strong's 'Modern Homebrew Techniques' that he adds "about 1/4 tsp of 10% phosphoric acid per 5 gallons of RO water to achieve a pH of 5.5 at room temperature" ...... "to reach a good mash pH of about 5.1 to 5.3 (with a pale grist)". However, my recipe software - Brewer's Friend - indicates I need substantially more 10% phosphoric to achieve the same effect, more like 1/2 tsp per gallon! Am I misunderstanding something or making a mistake?

Are you adding any salts like Gypsum that help bring down the pH? If now, then you may find that you need more acid. The Brewer's Friend calculator is pretty solid in my experience; if you're getting a funky result I'd doublecheck that your inputs are correct.

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[Ian]

Thanks for your help. Yes, I do have some gypsum, epsom salts and calcium chloride in the recipe (4 g, 2g & 6g respectively), but still need 10 ml phosphoric (ca. 2 tsp) to hit 5.3 pH - a long way from the suggested 1/4 tsp per 5 gallons. I can't find any errors in my inputs, but wouldn't rule that out.

For background I've been all-grain brewing about 3 years, initially with well water (high alkalinity), which was fine for darker beers, then decarbonating that, and progressed to RO water with salts added for a target profile and pH. Using phosphoric to adjust RO water as a starting point sounds very attractive/simple, but the math doesn't seem to work for me.

[HydraulicSammich]

Get the Bru'n Water spreadsheet and never look back.

[hopfenundmalz]

Get the Bru'n Water spreadsheet and never look back.

^^^^^ this.

And I will add not all RO water is the same. Some can be like distilled, almost, and some have a bit of bicarbonate to contend with.

If you have a pH meter, use it to find out what you need.

[Ian]

Thanks guys, especially re checking the RO water pH; my system is small so possibly changing. I check periodically thru' the mash, but was looking for an easier set-up. Anyway, on to the brew tomorrow