Ph after RO Filter

[agentbud]

No, I do not have a Ph meter.
Yes, I know I need to get one.

Until then....
I recently bought a 4-stage RO filter (sediment, carbon, ro membrane and deion). I have a Ward labs report on my home water so I know what is going into the filter, including the Ph, which is 7.8.
Will the RO filter change the Ph level? If yes, is there any way to approximate what the Ph will be after outputting from the RO filter?

 

[marc1]

If you pull almost everything out if the water it will have practically no buffering capacity, so the pH will be irrelevant for brewing purposes.

 

[bracconiere]

If you pull almost everything out if the water it will have practically no buffering capacity, so the pH will be irrelevant for brewing purposes.

well along those lines, it should have a ph of 7? and it'd only matter what was effecting the ph either way and how many H+, and H- accepeptors and donors it had which would require a ppm, and mol weight of the mols in question?

 

[agentbud]

^^ Read it. Re-read it. Drank a beer and read it again. Do what?

 

[bracconiere]

^^ Read it. Re-read it. Drank a beer and read it again. Do what?

hey man, if you're getting into water chemistry, and had a beer...or two, maybe three! then like most molecules are rated in mol weight per gram but most of them are made of mostly C-H stuff that doesn't matter....it's organic...but they have a certain number of reactive groups that crontibute H+ or accept an H....


that the jist of buffering, i think? but if one molcule has a mol weight of say 200g/mol, and another one like 40, but the 200 one has more H+...it's pretty cool stuff if you have fun with it!

edit: citric acid has a mol weight of 192, but can donate three H+, but lactic acid has a mol weight of 90, and only one H+ donor...so you can see it's a bit off molecularly speaking....and HCl acid has a mol weight of 40, and still only one H+ donor....this is when you need pKa, pKb..and stuff over my head, but have fun reading about while drinking!

 

[bracconiere]

another way to look at it....hydrogen has a mol weight of 1, but they're hooked up to other stuff, which has mol weights varrying drasticly...but the Ph is based on how many horny H+ there are compared to how many H-oes are available? want to take it? and if a certain molecule has more or less H+, but fat or skinny, it matters doing water chemistry? at least that's the way my 4th grade brain gets it?

edit: and there are a few halogens and base metal too, that throw me kinda in a spin too...

 

[jerrylotto]

RO water is not buffered so pH will start around 7 but will change drastically with the addition of anything acidic or basic. I'm assuming that you add minerals cuz yeast don't do well without at least some calcium and a trace of magnesium and beer taste is going to be impacted by chloride and sulfate concentrations. Carbonate will acidify but is also a good buffer. In other words, it's not just pH that you should be thinking about.

After all your minerals are dissolved that's when you can adjust the pH and you want your strike water to be on the acidic side, but until you actually mash and measure the resulting pH you're not going to know if you're at the right level of acidity. I generally use phosphoric acid to get down to about pH 5.5 for my strike water, but I usually have to adjust again (slightly) after I mash in my grain.

 

[Dancy]

I generally use phosphoric acid to get down to about pH 5.5 for my strike water, but I usually have to adjust again (slightly) after I mash in my grain.

Isn’t it possible (depending on the recipe) your mash pH could drop below 5.2 if your adjusting your strike water to a pH of 5.5? It maybe that’s only an issue with grain bills with darker grains.

 

[bracconiere]

Isn’t it possible (depending on the recipe) your mash pH could drop below 5.2 if your adjusting your strike water to a pH of 5.5?

as far as i know when sparging you want the strike water acidic, slightly, so you don't get tannins? as you sparge you're raising the ph of the grain bed, and thus could get more tannins?

if that was a typo or not, i'm not sure....?

 

[jerrylotto]

It's possible with acidulated malt but I generally brew with two row and lightly toasted adjuncts. I've seen the mash pH go up from that of the strike water!

 

[bracconiere]

I've seen the mesh pH go up from the strike order!

wait, you've seen the ph go up when you dough in?

 

[jerrylotto]

Yup

 

[agentbud]

RO water is not buffered so pH will start around 7 but will change drastically with the addition of anything acidic or basic. I'm assuming that you add minerals cuz yeast don't do well without at least some calcium and a trace of magnesium and beer taste is going to be impacted by chloride and sulfate concentrations. Carbonate will acidify but is also a good buffer. In other words, it's not just pH that you should be thinking about.

After all your minerals are dissolved that's when you can adjust the pH and you want your strike water to be on the acidic side, but until you actually mash and measure the resulting pH you're not going to know if you're at the right level of acidity. I generally use phosphoric acid to get down to about pH 5.5 for my strike water, but I usually have to adjust again (slightly) after I mash in my grain.

Absolutely will be adjusting the water with salts to get it in line for the given beer style. My concern here was the Ph. If my tap water has a Ph of 7.8, I was wondering if it is still 7.8 after running through the RO filter or does the RO filter change the Ph. When I plug the water into beersmith I just wanted to be sure I get the starting Ph close to correct so that I do not overcorrect it for the mash (ie add too much/too little lactic, etc).

 

[jerrylotto]

Absolutely will be adjusting the water with salts to get it in line for the given beer style. My concern here was the Ph. If my tap water has a Ph of 7.8, I was wondering if it is still 7.8 after running through the RO filter or does the RO filter change the Ph. When I plug the water into beersmith I just wanted to be sure I get the starting Ph close to correct so that I do not overcorrect it for the mash (ie add too much/too little lactic, etc).

No - pH of 7.0 for pure water. Once you start adding salts however, this will change. A good rule of thumb I've noticed is that if CaSO4*2 H2O aka gypsum does not dissolve, you probably need a little more acid.

 

[marc1]

Absolutely will be adjusting the water with salts to get it in line for the given beer style. My concern here was the Ph. If my tap water has a Ph of 7.8, I was wondering if it is still 7.8 after running through the RO filter or does the RO filter change the Ph. When I plug the water into beersmith I just wanted to be sure I get the starting Ph close to correct so that I do not overcorrect it for the mash (ie add too much/too little lactic, etc).

The starting pH doesn't matter for RO water. If Beersmith is giving wildly different mash pH results for RO water of different pHs, then something is seriously wrong with it.
The grains in the mash are what has the buffering capability.

 

[Bobby_M]

Reiterating; the pH of the water does not matter. Do yourself a favor and use software like Brewfather and just select "RO water" as your source water profile. It will tell you the estimated mash pH given your entered grain recipe. With a few grams of gypsum and calcium chloride added, as well as some lactic acid, it will show you the new estimated mash pH.... adjust lactic addition accordingly.

 

[ScrewyBrewer]

@agentbud the following text, from the 'iSpring Water's Good' site, does a great job of explaining how RO water removes alkalinity, and why it turns acidic when exposed to the atmosphere.

"Reverse osmosis water is nearly pure water with a PH of 7. Reverse osmosis is a filtration method that removes more than 99% of all the contaminants in water. The result is nearly pure water, which has neutral pH of 7.

But if it’s exposed to air, RO water drops down to an acidic pH range of 5 – 5.5. Why? Pure water is very hungry. it actually grabs CO2 right out of the air! Within about an hour, a glass of pure RO water can drop from a pH of 7 down to a pH of 5.5 or lower and become acidic water. Alkaline water has a pH of greater than 7, so reverse osmosis water is not alkaline water. To alkalize it, you have to add calcium and other minerals to it."