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pH meter reliability

So I bought a pH meter a few months ago. Milwaukee MW101. I calibrated it and I began using it to confirm pH adjustments that I made with Brunwater and found that I was over acidifying my mash.

After a few brew days it dawned on my that I should check my water pH prior to making adjustments. I had a water report from last year where Ward Labs said my water pH was 8.1 so I had been basing all my salt additions on that. The pH meter said my water was 7.1. On my last brew day it said 6.9.

My water comes from my private well and I know it can change seasonally so I figured I’d send the water in to Ward Labs to get another report. I just received it back and they state that my water pH is 7.7.

I put the sample in a 12 oz drinking water bottle that I had rinsed a couple of times with my water. I didn’t let the water run out of the tap all that long before I filled the bottle so I suppose there’s some chance the water had been sitting in the pipes for a bit.

.6 seems like a pretty big discrepancy to me. If I’ve mashed at 5.6 then I could actually be mashing at 6.2 and risking extracting tannins. I haven’t noticed any astringency in the beer.

I’m kind of thinking I can right this off to improper packaging of the water. SWMBO picked up a little test kit from a local water company so I’m thinking I’ll send them a sample to get a second opinion.

Do any of you have your water tested periodically and if so what kind of discrepancy do you see between the lab report and your pH meter?

Water pH has almost no bearing on what the water will do in the mash. The primary things are the alkalinity, calcium, and magnesium content. In addition, water pH can vary with temperature and any aeration that it might experience between the time you draw it from the tap and testing. The same thing applies to the pH testing that the lab performs. It’s nearly meaningless and could easily suffer from those same temp and aeration issues.

Don’t worry about this aspect.

Thanks Martin. Makes sense.

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