High Water pH

[emart85]

Hi all,

I initially had this in the AG topic section, but was directed here (still pretty new to the forum, sry)...

I'm about to do my first AG batch this weekend... I was looking at the water report today, and it tells me that the water pH is 9.7. That seems relatively high to me - should I be concerned about my mash pH with my basic water? Should I add phosporic acid or something of the like to bring the water pH down, or is this really not much of a concern? Unfortunately, I don't have any test strips here at the house...

My water report looks something like this:

Ca: 40 ppm
Mg: 5 ppm
Na: 58 ppm
SO4:174 ppm
Alkalinity: 32 ppm
Total Hardness (as CaCO3): 116
pH: 9.7

I'm still learning what to look for in a water report, so any help would be greatly appreciated. Thanks!

 

[ajdelange]

Let's assume you use about 1 quart of water per pound of grain or roughly 2 liters per kilogram. It's going to take less than 2*32/60 i.e. about 1 mEq of acid to bring the 2L of water to pH 5.4 but roughly 5 - 7 to move the pH of the kilogram of grain to pH 5.4. So yes, you need acid but not for the water so much as for the grain. Notice that the number I used in the calculation is 32 - the alkalinity. This is a measure of the acid required to shift the pH of the water to pH 4.5 irrespective of its pH out of the tap i.e. as far as acid addition for brewing the pH is useless information but you must know the alkalinity. That said it is unusual to have a pH as high as 9.7 especially with an alkalinity as low as 32. Are you sure you have those numbers right?

 

[emart85]

Let's assume you use about 1 quart of water per pound of grain or roughly 2 liters per kilogram. It's going to take less than 2*32/60 i.e. about 1 mEq of acid to bring the 2L of water to pH 5.4 but roughly 5 - 7 to move the pH of the kilogram of grain to pH 5.4. So yes, you need acid but not for the water so much as for the grain. Notice that the number I used in the calculation is 32 - the alkalinity. This is a measure of the acid required to shift the pH of the water to pH 4.5 irrespective of its pH out of the tap i.e. as far as acid addition for brewing the pH is useless information but you must know the alkalinity. That said it is unusual to have a pH as high as 9.7 especially with an alkalinity as low as 32. Are you sure you have those numbers right?

That's what the city report from last year says. I know, it seemed awfully high to me as well. I'm not as concerned with the alkalinity, since I know there are things you can do to get yourself in the correct residual alkalinity window (as you mention)... I may have to end up getting a ward labs report or something more specific to my tap water to be sure.

 

[emart85]

I suppose what I'm getting at here is - will the pH of my mash and/or lautering water have that much of an effect on the actual mash pH? Most of the mash pH calculators do not consider the strike water pH, only the grain bill, to calculate mash pH.

 

[Kaiser]

That said it is unusual to have a pH as high as 9.7 especially with an alkalinity as low as 32. Are you sure you have those numbers right?

I'd say that you need either low alkalinity or low calcium to have a stable water pH that high. Otherwise CaCO3 would precipitate and the pH and alkalinity (caused by carbonate) would fall until the CaCO3 solubility equilibrium is reached.

Kai

 

[GotPushrods]

I used to live in the KC area and can confirm that the pH is often quite high. I'm looking at an old report from summer 2006 I just found: pH 9.8, Total alkalinity 38 mg/L. My father has worked in the water industry there for decades, I'll have to ask him why that is. Could be a number of reasons.

Fortunately, it is not buffered strongly. (Low alkalinity) The alkalinity is what you care about, it tells you how easily pH will move. The pH of the water itself is rather unimportant. The carbonates should be the only significant buffer in tap water. There is something else going on here, but I can tell you from experience that whatever makes the pH 9.5+ is not buffering it strongly. It still behaves like sub-50 alkalinity water.

 

[Kaiser]

In order to reduce pipe corrosion municipal water treatment commonly includes the addition of a strong base. Because the water is so weakly buffered slight changes of the water alkalinity from the source can lead to noticeable pH changes due to the addition of the base.

I think Martin would be the best to answer this since he does work in that field.

Kai

 

[ajdelange]

I suppose what I'm getting at here is - will the pH of my mash and/or lautering water have that much of an effect on the actual mash pH? Most of the mash pH calculators do not consider the strike water pH, only the grain bill, to calculate mash pH.

No. As indicated earlier it is the water's alkalinity that is the most important water related parameter. For example with your water's alkalinity of 32 and pH of 9.6 it would take 0.57 mEq of acid for each liter of water used in the mash to bring that water to pH 5.4. This time I did an actual calculation rather than just WAGing it as I did last night. Were your water's pH 7 with that same level of alkalinity it would take 0.54. That's only a 5% difference. Were your water well water with a pH of 6.4 (like mine) it would take 0.50 which represents a 12% reduction relative to 57. This is fortuitous for the spreadsheet designers because having to consider pH in their offerings would complicate things quite a bit for them.


It has been noted that water authorities often adjust the pH of their product. This may happen as a part of treatment. For example, if your source water is really hard it may have been softened with lime and that can raise pH (lime is a pretty strong base). Or the water may have had alkali added to it in order to cause small amounts of calcium carbonate to precipitate inside the mains thus protecting them and prolonging their life. This water has a saturation index of 1.15 meaning that its pH is 1.15 units above the pH at which scale can be expected to start to form. This leads one to suspect that this may be the reason why the pH is so high but I'll note that it is about 1 pH unit above the EPA's recommended maximum for that parameter (though it's a secondary limit).

Finally, there is no reason to be concerned about the alkalinity not so much because there are things that you can do about it as because there just isn't that much of it.

 

[mabrungard]

It only took a few minutes to find. The KCMO water is 'Misery' River water that is lime-softened and rapid-sand filtered.

Reviewing the high sulfate content of that water, its apparent that they neutralize the softened water pH with sulfuric acid and it appears that they are not first conditioning the softened water with CO2 to reduce the acid demand. So, there is more sulfate in the water then there has to be, but I guess their approach is more expedient.

The high pH value in the treated water is a result of the lime softening process and their desire not to take the water pH too low, which increases water corrosivity in the pipes. Many municipalities are currently struggling with copper corrosion and elevated copper concentration in their wastewater effluent. Therefore, they are very likely to adjust their water treatment to reduce the water corrosivity. That means a higher pH.

This water hardness is mostly Permanent Hardness with the high sulfate content. The chloride level is probably in the 25 ppm range. Its too bad the city doesn't use a mix of hydrochloric and sulfuric acids, but it probably comes down to sulfuric acid being cheaper to use. The other thing that is biting municipalities is that chloride in the wastewater effluent is becoming more regulated. So they may not want to add any more.

The other thing that I see in cities is that homeowners want even softer water in their house and they add an ion-exchange softener. Those things dump a huge amount of chloride into the wastewater. The city then has to grapple with regulators if its too high in their wastewater.

So, the alkalinity of the KCMO water is modest, but the sulfate is pretty high. It should make a good pale ale or IPA. There might be a need for dilution for softer styles.

 

[emart85]

Thanks for everyone's responses! That all makes a lot of sense, and when i mashed this weekend my pH was right in the 5.2-5.4 range without any acid addition, so everything turned out just fine. Glad I got this input to ease my mind!