Hello, I have moved to a new house that came with a under the sink RO filter. The water has a pH of 5. Is this to acidic for brewing? I did a search and found little info about low pH, I did find one article that said low pH can cause problems with hot trub development. Is there a way to raise the pH of the water without negatively effecting flavor? Any information would be appreciated.
Probably not, but there’s a lot more to it than that. The pH of the water doesn’t really matter. It’s the mash pH that matters.
RO PH is normal/typical 5-6ishPH.
as Denny indicated- not relevant for brewing purposes. alkalinity and buffering capacity (or lack thereof) of your water drives where your mash PH will fall in the absence of any treatments with acid and brewing salts.
If you download Bru’n Water and read the “Water Knowledge” tab, you will be well on your way. RO water is good for brewing, but you will want to add minerals back for a variety of reasons.
I suppose that if you made a very dark beer (dark grains are more acidic and will lower mash pH) and you also added any amount of CaCl or CaSO4 (both of which also lower mash pH) then your mash pH could be lower than the standard 5.2 to 5.4.
While this makes a few folks cringe, I am one of those that has chosen to brew exclusively with RO water and build my profiles and manage pH with minerals and liquid acid. I highly recommend https://sites.google.com/site/brunwater/water-knowledge for a strong introduction into water chemistry.
+1 same here. no good way to brew with my well water.
PH is extremely easy to manage with software when your water is virtually stripped down.
+2. Exactly. Starting with the same blank slate each time (and avoiding crappy Indiana water), then using Brunwater makes pH control and fine tuning for style a breeze. I wish I’d done it this way sooner.
Carbonic acid in equilibrium with atmospheric CO2 causes RO to be slightly acidic. There is not enough carbonic acid in RO to have a significant effect on mash pH, which is what is important. See other posts about controlling mash pH.
I thought distilled water was pH 7? How can RO be lower?
Thank you all for all the quick information. Ive used the Brewers Friend water calculator in the past for adjustments. Guess I’ll just brew and see what happens. My city water is used by two local breweries. I called both of them and they just carbon filter the water. So that may be my next equipment purchase. Thanks again to all.
in theory distilled is neutral; however i have yet to get a PH reading from distilled that was 7. water absorbs Co2 (and when dissolved in water, forms carbonic acid) from atmosphere and result is more acidic water. my readings for distilled have always been in the 6.xx range.
Seems like RO would be a tad lower than distilled due to the trace amount of minerals present (chloride, sulfate and their ability to drop pH), depending on what the trace amounts consisted of, of course.
EDIT - I could always be wrong, though. 
Interesting. Thanks for clearing that up for me.
RO water can actually have fairly low pH that can easily be lower than distilled water. The reason is that some water supplies have dissolved gases, such as CO2, in them. Dissolved gases can easily permeate through the RO membrane into the treated water. That can drive the pH of RO water very low. In most cases, the gas content is minor and there is little problem. Some water supplies have to be run through an air-stripping tower to reduce that gas content to avoid this problem.
would this ^^^^^ impact how your software accounts for impact RO water, salts, and malts has on expected PH of the mash?
I have mentioned this many times on many boards but probably not here… RO water can be all over the place. Many brewers have told me that RO water is close enough to distilled water that you should just treat it like distilled. I’m sure that’s true in some cases. I used to get bulk RO water from the grocery store… bring empty, blue 5-gallon bottles and fill it up. I was treating it like distilled but my results were really discouraging. I took some of that RO water and sent it to Ward Labs and found that there were still some high numbers including bicarbonate at 50ppm, high dissolved solids, etc. I’m sure that most homebrewers who have an RO system in their home are careful about system maintenance, etc. The point is that distilled should be pretty much ZERO across the board while RO may have numbers that are higher.
You’re right. That’s why I carry a TDS meter to the store when I fill my RO jugs. If a store’s machine reads much above 25ppm TDS, I go to a different store. Brunwater does account for the difference between RO and distilled, within reason. This assumes water within the acceptable TDS range. I definitely wouldn’t buy RO without a TDS meter. I went to buy RO on my last beer and the water was well over 50ppm TDS - I went elsewhere.
I bring my TDS meter with me as well.
Smart. These stores must think “you can’t tell what’s in the water by looking at it so it must be good!”. 