Loooow ABV, why?

Two brews on same day, both only attenuated about 50-60%, what the heck!?! I’m leaning towards mash water pH, Here’s the stats:
OG 1045, 1046
FG 1020, 1030 respectively
Mashed @ 152 for 60,
Boiled 60,
Cooled in, added O2 and fermed @ 68-69 for 21 days.
Pitched happy London ale and a French saison. Initial ferm was great.
Grain bills 90-95% 2-row or pils, had about 5% acidulated in saison. The other is a bastardization o Elevenses. Should have both been super fermentable.

Only X-factor is water- I did no treatment of the water; It’s a well that I’ve never checked hardness or alkalinity, pH is in high 7’s I think. Now waiting on ward labs results.

Could this water source restrict fermentation THAT much!?!?! I’m all ears boys and girls, please throw whatever ya got at me.
Thanks for your time.

Have you brewed with the water before?

Have you checked calibration on your thermometer? Are you measuring FG with a refractometer?

I’m not one of the water experts here and there are some good ones so I think you will get more info but 7 is a little high on the ph. 5.2 is the normal to shoot for. I assume the 7 just the water, not the mash though.

Back when we were on a well I mixed the water with store bought or softened water to get the ph down. Softened water I knew wasn’t a great idea but it worked in a pinch. Lactic acid helped also.

You would think the acid malt would help in the Saison. Your water test may tell the tale.

Some will say that with today’s highly modified malts it isn’t necessary but have you tried a simple iodine test to check for complete conversion?

I have brewed with this water before, never checked FG on all grain from it- just moved back to this source after a few years of brewing elsewhere.

Thermometers are all good, have multiple, electric, analog and dairy- everyone’s in range.

I have been using a refractometer, and I’ve calibrated it with distilled.

I’m NOT monitoring pH o mash, but yeah I think potentially the acidulated and roast malt in each recipe respectively surely dropped pH some, idk how much.

HD4, how do you determine how much lactic to use? Just in mash or in sparse water too?

And that’s a big negatory on the iodine test. But you can bet your bloomers I’m gonna do every test known to man on my next batch. Thinking I’ll basically replicate the saison and with all else the same I’ll alter the water once I get the data from the test.

Are you correcting your refractometer reading based on the presence of alcohol? A refractometer will read artificially high when there is alcohol present in the beer rendering the measurement inaccurate. There are online refractometer calculators that will provide you with a reasonably accurate “corrected” value based on your OG and current Brix measurement post fermentation. I suspect that your true terminal gravity is in-line with what you expect.


If the alkalinity is really high it takes a lot to get the ph level to drop into the low to mid 5 range, with out diluting the well water with distilled or r.o. the malt alone isn’t going to drop the ph much. I typically have to use about 80 percent distilled to my well water. Then then malt will lower it to where I want it, then I add a little lactic acid to the sparge water to get where that needs to be. I use Brun water for calculation.

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That was a long time ago but it wasn’t much. Something like .5ml per lb of grist. I added it to the mash water and not the sparge I think. Then read the ph. Have been away from the well water for almost ten years and the public supply we have works without much attention. It was much less scientific than now. I used the old fashion ph strips that were not easy to read. I was kind of winging it and seeing how things turned out.