RO Water Sanity Check

I recently started using RO water produced from this thing:

Countertop Portable Universal 5-stage Reverse Osmosis RO Purification Water System with DI Deionizing Mixed Bed 0PPM postfilter

The TDS meter (cheap amazon thing) reads 0 ppm. I used Bru'n Water to create a water profile for a Kolsch 15 lb pils, 8oz flaked wheat, 3 oz Acid Malt. Added 2.5 grams Calcium Chloride to mash water of 5.7 gallons. Bru'n water had my PH target at 5.41, but actual PH was closer to 5.1, and I had to tweak the mash with some pickling lime to reach 5.3. Ph meter is a milwaukee ph 53 and I calibrated to 4.01 solution, also chilled mash sample to room temperature.

Is this low PH common using RO water? I know there are lot's of variables here (malt, strength of acid malt etc...) but am I missing something big or is this sort of thing common? Am I just going to have to keep good notes and work it out? Any pointers or a sanity check of yea..well that's what you have to do would be helpful.

Topic mash-ph homebrew

Category Mac

1
answered at

I would expect RO water to lack the carbonates to buffer your mash pH. The water I tend to brew with has pH 7.2-8.0 mean 7.61 depending on time of year and a hardness as CaCO3 of ~270 ppm. This offers a fair amount of buffering. As you are only adding calcium chloride to the solution and no carbonate I am not surprised that your pH is more acidic than anticipated.

I have personally never used the Bru'n water calculators myself, I tend to use good old trial and error, and dial in with a tweak here or there as required to get the number lining up.

Regarding pH meter calibration, it is usually best to calibrate with 2 separate buffered solutions one acid and one neutral or base.

Reading a few posts on other homebrew forums, many of them suggest using 50/50 RO/tap water to balance out their brews, or 60/40 40/60 depending on the target I would suggest trying this, as it will leave trace level of other salts in there.

1
answered at

Your ro water shouldn't effect your ph also you can do a quick purity test with a multimeter set it to the mega ohms range and keep the probes about a cm apart they should read about 18Mohm. If that's the case you will have very pure watter.

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