First Time BIAB - City Water Analysis

[thomer]

I have been extract brewing for the past year and am now moving into BIAB. I have a 15g kettle so can do full volume boils. I have posted elsewhere on this forum and the members have been very helpful. I was asking questions about water and someone referred me to this area. I have attached a 2020 water report from the City of Phoenix, however I know these reports do not include a lot of brewing specific information. I have been reading A Brewing Water Chemistry Primer. I suspect looking at the City of Phoenix Water report, I am better off with 100% RO water plus the baseline additives rather than a dilution, but interested to know your thoughts. I plan on getting my water tested and get a full report.

Also I like to brew mostly IPAs, so which of the 4 categories mentioned in the report would fit into? Pils/Helles, British Beers, (obviously not Stout/Porter) or Minerally Beers?

Thanks for reading.

 

[Silver_Is_Money]

Unless I missed them, all of the mineral ions pertinent to beer brewing are missing from your water report.

You want to see Calcium, Magnesium, Chloride (which is not Chlorine), and Sulfate in addition to Alkalinity. Knowing the iron content is also a plus. I did see Sodium.

If your water comes from more than one source, that is also problematic.

 

[thomer]

No you didn't miss them, they are just not listed. I think I need to send my water off for a test. Thanks for the reply.

 

[Silver_Is_Money]

No you didn't miss them, they are just not listed. I think I need to send my water off for a test. Thanks for the reply.

Don't bother if your water is multi-sourced.

 

[thomer]

Don't bother if your water is multi-sourced.

That is the problem. Phoenix is now the 5th largest city in the US with 5.5m population.
I think I am going down the route of RO with additives.

 

[CascadesBrewer]

That is the problem. Phoenix is now the 5th largest city in the US with 5.5m population.
I think I am going down the route of RO with additives.

If you reach out to your water company, they might send you some more info. I have heard of water companies that have a "brewing report" that they send to people that ask. When I reached out to my water company they directed me to a web site where I could look at more detailed water testing for my supply.

There are pluses and minuses of getting a water report and using testing data and both are useful. I have a Ward Lab report, but it is only what my water was on the specific day that I took the sample. Testing data may not match what actually comes out your tap. Looking at data from the county as well as reports from other brewers/breweries in the area I have a general feel of the ranges of ions. I have tweaked some values from my Ward Labs report to get a profile that is likely to be closer to what is coming out of my tap on any random day. I know my tap can vary some but I am not too worried about a +/- 20 ppm for most ions.

Also, I am sure there are a lot of brewers in the Phoenix area that have experience using or adjusting the local water. You might reach out to homebrew shops or homebrew clubs for information.

 

[thomer]

Also, I am sure there are a lot of brewers in the Phoenix area that have experience using or adjusting the local water. You might reach out to homebrew shops or homebrew clubs for information.

Thanks for the reply. I did reach out to my local homebrew store yesterday and they tell me pretty much no-one he knows brews with the city water here. He very kindly gave me a spreadsheet detailing the additives I can put in RO water for different styles of beer. I have been told this may not brew really 'great' beer, but will give me 'good' beer I can build on. So I will use this for my first few AG brews and take it from there.

 

[CascadesBrewer]

Thanks for the reply. I did reach out to my local homebrew store yesterday and they tell me pretty much no-one he knows brews with the city water here. He very kindly gave me a spreadsheet detailing the additives I can put in RO water for different styles of beer. I have been told this may not brew really 'great' beer, but will give me 'good' beer I can build on. So I will use this for my first few AG brews and take it from there.

It does seem that the Phoenix area water is pretty bad for brewing. Have you read this thread? phoenix water profile 5-6-2008

I am a bit curious about that "spreadsheet detailing the additives I can put in RO water for different styles of beer". I feel like a resource like this should be wide spread, but I have not seen such a resource.

 

[thomer]

It does seem that the Phoenix area water is pretty bad for brewing. Have you read this thread? phoenix water profile 5-6-2008

I am a bit curious about that "spreadsheet detailing the additives I can put in RO water for different styles of beer". I feel like a resource like this should be wide spread, but I have not seen such a resource.

Here you go. Ignore the multiple tables, it's actually just one.

 

[marc1]

Here you go. Ignore the multiple tables, it's actually just one.

Odd that it doesn't include any acid for pale beer.

 

[CascadesBrewer]

Here you go. Ignore the multiple tables, it's actually just one.

Thanks! Based on the file name, I have to guess this is the sheet included by Anvil with the Foundry. I had heard that John Palmer created some simple water chemistry stuff for the Foundry's manual. It seems like a reasonable first step:

• For "hoppy" beers add 1 g/gal of Gypsum (aka Calcium Sulfate) and 0.5 g/gal of Calcium Chloride
• For "malty" beers add 0.5 g/gal of Gypsum (aka Calcium Sulfate) and 1 g/gal of Calcium Chloride
• For "amber" beers add 0.5 g/gal of of Baking Soda
• for "dark" beers add 1 g/gal of Baking Soda

I am not sure if this is "gallons of mash water" or if the same would also be added to any sparge water used.

I could take it one step further and say to add 0.75 g/gal of both Gypsum and Calcium Chloride for a "balanced" profile.

I don't brew with RO myself, so I don't have a feel for pH adjustments needed with RO. I have to add acid to my tap water for pale beers, the with lack of buffering in RO water is acid often needed for pale beers?

 

[TestTickle]

I don't brew with RO myself, so I don't have a feel for pH adjustments needed with RO. I have to add acid to my tap water for pale beers, the with lack of buffering in RO water is acid often needed for pale beers?

In most cases, I would say yes, but it may depend on your water to grain ratio. With RO or distilled, I believe that the water to grain ratio has an opposite affect on pH as it does when using tap water. A full volume BIAB mash for a pale beer may not need much if any acidification, but the same beer using some of the water for sparging (thus resulting in a lower water to grain ratio) will most likely need some acid.

I'll have to go back and look through some older recipes, but I seem to recall noticing this when I decided to use distilled for a lager that I was brewing. Normally, I would expect the pH to be higher when the water to grain ratio is higher (as with BIAB), but when using distilled and targeting the same water profile, it was actually lower and I ended up not needing any (or much) acid.

 

[Silver_Is_Money]

In most cases, I would say yes, but it may depend on your water to grain ratio. With RO or distilled, I believe that the water to grain ratio has an opposite affect on pH as it does when using tap water. A full volume BIAB mash for a pale beer may not need much if any acidification, but the same beer using some of the water for sparging (thus resulting in a lower water to grain ratio) will most likely need some acid.

I'll have to go back and look through some older recipes, but I seem to recall noticing this when I decided to use distilled for a lager that I was brewing. Normally, I would expect the pH to be higher when the water to grain ratio is higher (as with BIAB), but when using distilled and targeting the same water profile, it was actually lower and I ended up not needing any (or much) acid.

For alkalinity free water the water volume has little to no impact upon the required amount of acid required, since all of the base that exists whereby to be acidified resides within solely the grist. And ditto for an acidic grist that requires the addition of a basic substance. Neutral pH water hardly enters into chemical equations at all, which is precisely why analytical lab level acid and/or base titrations to targeted pH's are carried out within deionized water.

 

[TestTickle]

For alkalinity free water the water volume has little to no impact upon the required amount of acid required, since all of the base that exists whereby to be acidified resides within solely the grist. And ditto for an acidic grist that requires the addition of a basic substance. Neutral pH water hardly enters into chemical equations at all, which is precisely why analytical lab level acid and/or base titrations to targeted pH's are carried out within deionized water.

Looking back, I believe Bru'n Water didn't calculate as drastic of a change in pH as other software did with RO water when doing full volume mash BIAB. It was several points higher, but it largely depends on the amount of minerals being added back to build up the water profile. The pH without acid ended up being just over 5.4, which for me wasn't worth adding any acid. A ml of lactic acid would have brought me closer to 5.2.

 

[TestTickle]

I should add that this is purely based on the pH calculations of software, I don't have notes of what the measured pH was.

 

[Silver_Is_Money]

If you begin with (for example) pH 5.50 deionized water that has right close to zero buffering capacity (by definition, being ion free sans for a minescule acid addition whereby to bring it to pH 5.50) and you then fully double its volume with more of the very same deionized water, you will now measure a pH of 5.80.

But beer grist contains a multitude of relatively strongly buffering agent substances, and if your Wort is pH 5.50 and you double the volume of your Wort via an addition of perfectly neutral water (such as deionized or very good distilled or RO) the resulting pH will be about 5.51 (as opposed to 5.80), because the very definition of a buffer is that it is a substance which resists change(s) in pH.

At pH 5.50 the molarity of H+ (acid ions) in solution equals:
10^-5.50 = 0.000003162 molar H+

Add to this deionized water whereby to double its volume. Now H+ is half, or 0.000001581 molar H+.

And the pH is now :
-Log(0.000001581) = 5.801 pH

But only for the case of no buffering substances present...

 

[Silver_Is_Money]

Looking back, I believe Bru'n Water didn't calculate as drastic of a change in pH as other software did with RO water when doing full volume mash BIAB. It was several points higher, but it largely depends on the amount of minerals being added back to build up the water profile. The pH without acid ended up being just over 5.4, which for me wasn't worth adding any acid. A ml of lactic acid would have brought me closer to 5.2.

If any software exhibits anything other than the most minuscule of perceptable changes in pH for Mineral and Alkalinity free buffered Wort solutions in conjunction with a halving and/or doubling of the water volume, then something is seriously wrong with the software.

 

[CascadesBrewer]

If any software exhibits anything other than the most minuscule of perceptable changes in pH for Alkalinity free buffered Wort solutions in conjunction with a halving and/or doubling of the water volume, then something is seriously wrong with the software.

Is this assuming no Calcium additions? The attached sheet states to add Gypsum or Calcium Chloride on a grams per gallon rate. Playing around with this in Bru'n Water (10 lbs 2-Row, 1 g/gal Gypsum, 0.5 g/gal Calcium Chloride, 100% Distilled Water) shows a mash pH of 5.49 with a 3 gallon mash and 5.22 with a 8 gallon mash. Does that seem expected?

 

[Silver_Is_Money]

I have no clue as to what to expect for 'Bru'n Water', not being a user of that software. But my math modeled example as seen above is for the maximum pH impact of water doubling when the water involved is both mineral and alkalinity (and thus buffer) free. And I'm trying to also express the lack of change in pH for mineral and alkalinity free water for the case of volume doubling when a buffer (such as a beer recipes grist) is introduced into the water.

 

[TestTickle]

If any software exhibits anything other than the most minuscule of perceptable changes in pH for Mineral and Alkalinity free buffered Wort solutions in conjunction with a halving and/or doubling of the water volume, then something is seriously wrong with the software.

Chalk it up as software miscalculations then? I'm no chemist, so I am not doubting what you are saying. All I can say is that I was able to duplicate this behavior in Bru'n Water, Beersmith and Brewfather. Each one calculated it slightly differently, but were each consistent in that using a grain bill with an SRM of 3.3 and RO water, the pH changed depending on amount of strike water used, with identical gram/gal ratio of mineral additions. For example, mashing with 2.66 gallons is giving me an estimated pH of 5.54 while doing a full volume mash with 6.24 gallons drops it to 5.42.

 

[TestTickle]

Also, as I noted earlier, I was not expecting this behavior, so logic tells me that you are absolutely correct.

 

[Silver_Is_Money]

Chalk it up as software miscalculations then? I'm no chemist, so I am not doubting what you are saying. All I can say is that I was able to duplicate this behavior in Bru'n Water, Beersmith and Brewfather. Each one calculated it slightly differently, but were each consistent in that using a grain bill with an SRM of 3.3 and RO water, the pH changed depending on amount of strike water used, with identical gram/gal ratio of mineral additions. For example, mashing with 2.66 gallons is giving me an estimated pH of 5.54 while doing a full volume mash with 6.24 gallons drops it to 5.42.

So what you are saying/observing is that for these various of softwares neutral and ion free water acts as if it is demonstrably acidic. That is a serious contradiction, is it not? How can water that is by definition ion free act as if it has a plethora of abundant H+ (acid) ions that it can deliver whereby to lower the pH in and of itself simply via adding more of such water?

OTOH: Free of extant buffering, such waters pH would naturally rise 0.30 pH points upon water doubling, due to the halving of initial H+ density.

 

[CascadesBrewer]

BTW, the Anvil Foundry manual (from which the table comes from) can be found here: https://www.anvilbrewing.com/pub/media/wysiwyg/ANV-Foundry_V7.pdf

As far as I can tell, the recommended additions would produce a reasonable mash pH with enough grain for a 1.045-1.060 using a typical Anvil Foundry mash (either full volume or a little sparge water).

I have found that pH is one of the harder aspects to fit into the "simple water chemistry additions" solutions that I have seen. Since nobody should be mashing with pure RO water, the amount of grain and mash thickness can have a big impact. Plus there is a lot of variance in "pale" to "amber" to "dark".

 

[TestTickle]

So what you are saying/observing is that for these various of softwares neutral and ion free water acts as if it is demonstrably acidic. That is a serious contradiction, is it not? How can water that is by definition ion free act as if it has a plethora of abundant H+ (acid) ions that it can deliver whereby to lower the pH in and of itself simply via adding more water? Free of buffering, the waters pH would naturally rise 0.30 pH points upon water doubling, due to the halving of H+ density.

Only when minerals are added back. If minerals are left out of the equation, the behavior is what I would expect, which is that the pH actually rises with a higher water to grain ratio.

 

[Silver_Is_Money]

Only when minerals are added back. If minerals are left out of the equation, the behavior is what I would expect, which is that the pH actually rises with a higher water to grain ratio.

Why would you expect that (I.E., a measurable rise in pH) in the presence of grist delivered buffering agents that (by definition) resist changes in pH?

 

[TestTickle]

Why would you expect that in the presence of grist delivered buffering agents that (by definition) resist changes in pH?

Because that is what I have experienced in the past. I noticed a change in mash pH when I started doing full volume BIAB brews.

 

[Silver_Is_Money]

Because that is what I have experienced in the past. I noticed a change in mash pH when I started doing full volume BIAB brews.

Mash pH tends to rise to its final pH as the Mash progresses in time. Sampling early generally results in a false low mash pH reading. Mash pH measured at 15 minutes will invariably be lower than mash pH measured at 60 minutes.

It would certainly be the case that you would witness higher Mash pH for doubled mash water volume when the case is that Alkalinity is present within the water. Doubling the water volume doubles the mEq's of Alkalinity.

 

[TestTickle]

Mash pH tends to rise to its final pH as the Mash progresses in time. Sampling early generally results in a false low mash pH reading. Mash pH measured at 15 minutes will invariably be lower than mash pH measured at 60 minutes.

It would certainly be the case that you would witness higher Mash pH for doubled mash water volume when the case is that Alkalinity is present within the water. Doubling the water volume doubles the mEq's of Alkalinity.

Yes, I am referring to mash pH measured at 15-20 minutes into the mash. So does it make any sense that using the same grain bill with RO water and minerals (chloride, sulfate and magnesium) added back in would result in the opposite behavior?

 

[Silver_Is_Money]

Yes, I am referring to mash pH measured at 15-20 minutes into the mash. So does it make any sense that using the same grain bill with RO water and minerals (chloride, sulfate and magnesium) added back in would result in the opposite behavior?

I'm not sure as to what you are saying is the opposite behavior.

Calcium and Magnesium lower mash pH, albeit to only half or less that predicted by most software, likely including all of those softwares which you have mentioned, as observed first by AJ deLange (who observed ~half), and then by Barth and Zaman (who observed generally less than half).

My question is still: How can Wort act as if it has little to no buffering capacity, and thereby permit a noticeable rise in pH with the simple doubling of the water volume via addition of ion free water, when it factually has an appreciable and reasonably well understood as to mEq/Kg.pH magnitude buffering capacity by which to resist change in pH?

 

[Silver_Is_Money]

If you have 5 gallons of 50 mg/L (ppm) Calcium water, and you double this 50 mg/L calcium waters volume to 10 gallons via the addition of yet more of the very same 50 mg/L calcium water, you have just doubled the mEq's (milliequivalents) of extant pH reducing calcium ions. The impact of this would be twice the calcium induced reduction in mash pH.

 

[marc1]

Wasn't there a big discussion a few years ago in the Brew Science forum on the issue of some software showing inaccurate swings in mash pH with changes in the water to grist ratio? I thought that was all hashed out and resolved a long time ago.

 

[Silver_Is_Money]

Wasn't there a big discussion a few years ago in the Brew Science forum on the issue of some software showing inaccurate swings in mash pH with changes in the water to grist ratio? I thought that was all hashed out and resolved a long time ago.

Was there? Yes!
Was it all hashed out? It could be that it was, but I'm not fully convinced.
A far better question might be: Was it all hashed out adequately, or satisfactorily, or does it still lurk in the background?

 

[marc1]

I just fired up BrunWater 1.25. I put in a grist of 10 lbs of 3L base malt.

Here are the predicted pH values for some different conditions. Is this what you see @TestTickle ?

Water profile of all 0s, no additions:

Mash with 7.5 gallons of water (3qt/lb) the pH = 5.71. Mash with 5 gallons of water (2 qt/lb) the pH = 5.68. Mash with 2.5 gallons (1 qt/lb) the pH = 5.61.
So the predicted changes are fairly small until you get to thick mashes.


With 1g gypsum and 0.5 g CaCl2/gallon the changes are as follows:

3qt/lb pH = 5.18
2qt/lb pH = 5.33
1qt/lb pH =5.43

This trend would be expected as described in @Silver_Is_Money 's post #30 above. How close these predictions are to real measured values for different brands of 2-row I don't know.

------------------------------------------------------------------------------------------

When I first started measuring mash pH I did a timecourse and noticed the change over time. Now I measure at the end because it is consistent (i.e. no longer changing, so I'm not going to catch it at a intermediate pH) and is representative of the mash pH once everything is dissolved/hydrated/at equilibrium (is there a more correct term for this?).

Does anyone know if the timecourse of the mash pH change is related to the water to grist ratio?

 

[Silver_Is_Money]

What is the pH case for mineral and alkalinity free water as the mash thickness is varied?

 

[Silver_Is_Money]

The matter was actually settled in 2018 via hard science carried out and published as:
A Homebrewing Perspective on Mash pH III: Distilled-Water pH and Buffering Capacity of the Grist ∗
D. Mark Riffe † and Mick Spencer
(Dated: May 10, 2018)

As seen from this snapshot of their test results, mashes carried out in 2.5, 4, and 8 L/Kg. mash thicknesses varied hardly at all on overall aggregate. Some to most of the grist data was pH flat, some rose slightly as to pH, and some essentially equal sample quantity actually declined in pH slightly as the mash became extremely thin. Overall the best guess (as I see it at least) is for flat, meaning no real and repeatable overall change in mash pH as mash thickness varies from one extreme to the other. See this snapshot I captured from this excellent published research. My conclusion is (as stated several times above) that well buffered Wort solutions do not change pH when mineral and alkalinity free mash water is increased/decreased, at least within sane mash thickness limits.

 

[Silver_Is_Money]

In going from 2.5 L/Kg. (thick) to 8 L/Kg. (thin) the increase in water volume is 8/2.5 = 3.2X.

If no buffering was present then our pH 5.50 and thereby 0.000003162 molar as to H+ water (sticking with my above example) would have its H+ molar concentration density reduced to:
0.000003162 / 3.2 = 0.000000988 molar H+

And without any grist induced buffering what was initially 5.50 pH water would now be:
-Log(0.000000988) = 6.001 pH

Nothing remotely close to this degree of rise in pH is observed within the above posted hard data snapshot. Wort buffering keeps the pH from rising, when (critically) the data is observed on an overall aggregate basis.

 

[CascadesBrewer]

Something that I have wondered...which I think is in line with @thomer's original post about getting started with water adjusments...is there a simple "first steps" water chemistry strategy for somebody using RO that is maybe a step above the "add a teaspoon of calcium chloride...and maybe a few oz of acidulated malt" type advice?

There is the post from AJ on this forum: A Brewing Water Chemistry Primer
There is this blog post that I see recommended often: Water Chemistry – How to Build Your Water – Bertus Brewery

As somebody with a few years experience adjusting water starting with my tap water, I don't have a great feel for adjusting RO/Distilled water. My gut says that I would not follow or recommend either of those "simple" approaches. The recommendations above by John Palmer from the Anvil Foundry manual seem a little better (maybe).

I believe that Mash Made Easy has a "Distilled or RO Water Mineralization Assistant" that seems pretty useful. I don't use it myself just because I start with my own tap water. It has that typical hurdle that seems common with software that profiles are names like "Hoppy, Medium" so new brewers are left to figure out what profile fits their Saison, Pumpkin Ale, Baltic Porter, or Irish Stout. pH adjustment are left up to the brewer to figure out on different tabs. Most other software has the same or steeper learning curve.

I have always felt like it should be easier for a new brewer that is using RO water and brewing a 5 gallon batch of Czech Pils/Belgian Dubbel/German Wheat/Dark Mild/etc. to look up a recommendation for salt additions and pH adjustments.

 

[marc1]

Something that I have wondered...which I think is in line with @thomer's original post about getting started with water adjusments...is there a simple "first steps" water chemistry strategy for somebody using RO that is maybe a step above the "add a teaspoon of calcium chloride...and maybe a few oz of acidulated malt" type advice?

There is the post from AJ on this forum: A Brewing Water Chemistry Primer
There is this blog post that I see recommended often: Water Chemistry – How to Build Your Water – Bertus Brewery

As somebody with a few years experience adjusting water starting with my tap water, I don't have a great feel for adjusting RO/Distilled water. My gut says that I would not follow or recommend either of those "simple" approaches. The recommendations above by John Palmer from the Anvil Foundry manual seem a little better (maybe).

I believe that Mash Made Easy has a "Distilled or RO Water Mineralization Assistant" that seems pretty useful. I don't use it myself just because I start with my own tap water. It has that typical hurdle that seems common with software that profiles are names like "Hoppy, Medium" so new brewers are left to figure out what profile fits their Saison, Pumpkin Ale, Baltic Porter, or Irish Stout. pH adjustment are left up to the brewer to figure out on different tabs. Most other software has the same or steeper learning curve.

I have always felt like it should be easier for a new brewer that is using RO water and brewing a 5 gallon batch of Czech Pils/Belgian Dubbel/German Wheat/Dark Mild/etc. to look up a recommendation for salt additions and pH adjustments.

You can kind of see what things are generally recommended with those "yellow balanced" etc. profiles, but like most brewing ingredient decisions it's all personal preference. Experimentation and experience will guide you. Make a beer heavy in sulfite. Make a beer heavy in Cl. Make one heavy in both, and one light on both. See what they taste like.

Some styles have fairly easy to find recommendations - Czech/Bohemain pilsners are supposed to have very low mineralization. The last beer in this style I made was calculated as 39Ca and 69Cl.

Other styles, like NEIPA, have recommendations all over the place. People say 2:1 Cl:Sulfate, but that is pretty useless without an absolute value for something. There are also people who like them with more sulfate than Cl. You can pick something that you are comfortable with trying that might be in the middle-ish (say, 150:75) and go from there. Maybe try 200:100 for the next one and see what you think. Or 100:200 Cl to sulfate to see if you're contrarian.

In your case, even though you are starting with tap water, you are making adjustments and have targets for Cl and sulfate, right? Maybe even Na and Mg? You can get to those same levels from RO just as you can from tap. I think working from RO is easier because you don't have to deal with stuff that's already there - what you are doing now is harder. If you decided to switch to RO you shouldn't have a problem, although if you are lucky enough to have good tap water then you probably don't need to.

I'm not convinced that mash pH makes that big of a difference, as long as you are in the right ballpark. I doubt that I could tell the difference between a 5.3 and a 5.5 mashed beer.

 

[TestTickle]

I just fired up BrunWater 1.25. I put in a grist of 10 lbs of 3L base malt.

Here are the predicted pH values for some different conditions. Is this what you see @TestTickle ?

Water profile of all 0s, no additions:

Mash with 7.5 gallons of water (3qt/lb) the pH = 5.71. Mash with 5 gallons of water (2 qt/lb) the pH = 5.68. Mash with 2.5 gallons (1 qt/lb) the pH = 5.61.
So the predicted changes are fairly small until you get to thick mashes.


With 1g gypsum and 0.5 g CaCl2/gallon the changes are as follows:

3qt/lb pH = 5.18
2qt/lb pH = 5.33
1qt/lb pH =5.43

This trend would be expected as described in @Silver_Is_Money 's post #30 above. How close these predictions are to real measured values for different brands of 2-row I don't know.

------------------------------------------------------------------------------------------

When I first started measuring mash pH I did a timecourse and noticed the change over time. Now I measure at the end because it is consistent (i.e. no longer changing, so I'm not going to catch it at a intermediate pH) and is representative of the mash pH once everything is dissolved/hydrated/at equilibrium (is there a more correct term for this?).

Does anyone know if the timecourse of the mash pH change is related to the water to grist ratio?

This is exactly what I am seeing.

 

[marc1]

This is exactly what I am seeing.

OK - we're all on the same page now!

In this software, the mineralized water differences are trending as expected, and the RO water doesn't change much until thick mashes. Since real life use generally shouldn't use RO only, then it doesn't seem to be a big problem for practical applications.

Like all software, it's for getting an estimate of mash pH, and can't know the differences between malts that aren't part of its calculations (for BrunWater these are things like: different maltsters, lots, varieties of barley, etc.). It uses broad grain type and color values to make its estimates, along with water information. If you find that it is helpful in planning mineral and acid additions overall, then it serves your purposes.