RODI sparge water ph adjustment

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frontiercdk

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Hey guys,

I want to adjust my sparge water ph to 5.5

I am using RODI water no salt additions till boil. How much 88% lactic acid per gallon would I need?
 

Big Monk

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Hey guys,

I want to adjust my sparge water ph to 5.5

I am using RODI water no salt additions till boil. How much 88% lactic acid per gallon would I need?
Depends.

What issue starting water pH and alkalinity?
 

Vale71

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I assume you're doing this because you have a lot of dark/roast malts in your grist and don't want to undershoot your target PH?
If that is the case then just use your RODI sparge water as is. As RODI water has no buffering and will already be slightly acidic from CO2 pickup it will quickly reach the same PH as the mash as it traverls through the grain bed. With acid additions you only run the risk of over-acidifying.
 

Silver_Is_Money

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Conflating RO and DI as if they are one and the same might get you in trouble. High quality RO can approach (but never quite reach) true DI, but run of the mill RO typically exhibits a touch of alkalinity, and poor RO may have alkalinity at levels that should be addressed.

That said, I agree with @Vale71 that RO water can generally be used as is for sparging, with no acid treatment. But I also agree with @RPIScotty in that it depends upon the alkalinity.
 
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frontiercdk

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Conflating RO and DI as if they are one and the same might get you in trouble. High quality RO can approach (but never quite reach) true DI, but run of the mill RO typically exhibits a touch of alkalinity, and poor RO may have alkalinity at levels that should be addressed.

That said, I agree with @Vale71 that RO water can generally be used as is for sparging, with no acid treatment. But I also agree with @RPIScotty in that it depends upon the alkalinity.
Thanks for the quick response, I will get the alkalinity and ph numbers and post them. This is the first time I will be using this filter. Probably a good idea to know the alkalinity anyway, right? It is a RO and DI setup with a carbon filter.
 

Big Monk

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Thanks for the quick response, I will get the alkalinity and ph numbers and post them. This is the first time I will be using this filter. Probably a good idea to know the alkalinity anyway, right? It is a RO and DI setup with a carbon filter.
In a perfect world, your RO water will have low to no alkalinity. I actually asked about pH and alkalinity because I misread your post and didnt realize you were referencing RO/Distilled.

With that said, the presence of appreciable alkalinity in an RO source can be used to troubleshoot something wrong with the system, i.e. it might not be doing a very good job.
 

ajdelange

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I want to adjust my sparge water ph to 5.5
I am using RODI water no salt additions till boil. How much 88% lactic acid per gallon would I need?
Only one way to find out. Add some lactic acid to a gallon of water and see. This is what a lab would do (except they'd use sulfuric acid) if you sent a sample off to them for analysis. So put a gallon of water into a bucket and add a drop (0.05 ml) of lactic acid to see where the pH goes. It should take precious little acid to get you to 5.5. A drop of 88% lactic acid is about 12.5 N at pH 5.5 so a drop would provide about 0.625 mEq. It takes 0.03 mEq to lower the pH of a liter of DI water to 5.5 or roughly 0.12 mL/gal so if a drop took a gallon to 5.5 you would know that the alkalinity of the water was about .125 mEq/L (6 ppm as CaCO3). But you really don't care what the alkalinity is (except diagnostically). All you want to know is how much acid to add to get to pH 5.5. It should be around a drop per gallon - less if your RO unit has lowered the alkalinity level below .125 or so and more if it hasn't.
 
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frontiercdk

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Checked my Alkalinity with a hanna checker. It came out to be .5 dkH. This means the RODI setup is doing a good job right?

Do you still believe one drop per gallon would be a good starting point?
 

Silver_Is_Money

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Checked my Alkalinity with a hanna checker. It came out to be .5 dkH. This means the RODI setup is doing a good job right?

Do you still believe one drop per gallon would be a good starting point?
That is just a smidge less than 9 ppm alkalinity, at 8.924.

Presuming that 8.924 ppm alkalinity is indeed correct, and that your Hanna meter is scaled to read alkalinity as CaCO3 (and realizing that a precision alkalinity reading is difficult at such a low level), ~0.57 mL of 10% Phosphoric Acid per Gallon of this water should neutralize the alkalinity and bring this water to ~5.4 pH. And about 0.053 mL of 88% Lactic Acid should do likewise.

Most likely it is hardly worth the bother. For a ballpark 12 Plato recipe the mash pH difference between acidifying your RO mash water and not acidifying it is roughly on the order of 0.03 pH points.
 
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ajdelange

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One drop per gal would be a good place to start. You reported alkalinity of 0.18 mEq/L. One drop per gal would, per my earlier calculation, cover 0.125 mEq/L so you may find you need a bit more.

Note that at these levels it doesn't really much matter whether you hit, overshoot or undershoot pH 5.5.
 
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frontiercdk

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Thanks for taking the time... i'm in good shape now.
 
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