Fermentation pH 3.8 - Stalled Fermentation

[Alphaacid]

So the pH of my Milk Stout fell to pH 3.8, and it's stuck at 7.5P, the FG is suppose to be 4.5P. I'm assuming it's the low pH that has stalled my ferm? It's seems low, but I just measured my Wit and it's pH 3.8 as well, and the fermentation is great. Using compressed sterile air to oxygenate the wort...Maybe not enough DO?

My Water profile:

Calcium Magnesium Sodium Chloride Sulfate
(Ca ppm) (Mg ppm) (Na ppm) (Cl ppm) (SO4 ppm)
Mash Water Profile: 119 18 161 132 186
Mash+Sparge Profile: 59 9 79 65 91

The mash pH was 5.31, and sparge water was pH 7.0.

[mikeyrb1]

You have an under attenuated batch and you mention nothing about your yeast?

[Alphaacid]

Good point. Total forgot. Using US-05 at 80g/HL

[gitchegumee]

Well then it's not the pH...

US-05 works great at lower pH levels than you are reporting. And your pitch rate is fine. If you used fresh pitch of dry yeast for this, then look elsewhere for your problem. Lots of other possibilities, but 3.8 pH and 80g/hl fresh dry yeast won't slow down US-05. Sodium and chloride levels are a bit high, but that wouldn't likely stunt your ferment.

[Alphaacid]

I'm thinking it's lack of DO in the wort. They're using a compressor with sterile air, but I've found a ton of grease in the lines. The compressor says it's oil free, but it has pistons, so it can't be.

[Alphaacid]

The other thing I'm thinking is that it has been going down to 3C at night, and the building is cold all the time. The empty FV's are sitting around 9C, and as ferm slows they temp is dropping from 18-19C down to 16C, and this is when ferm begins to slow. So maybe it's not a stuck ferm, but just slow due to cold.

[Gbbc]

So, what is your grain bill and your mash temp? Day what is your fermentation at? What was your OG?