Adjusting Water pH

This is a question that I have never been asked and did a little digging. The reason for the digging is the very low pH of your well water. Most well water ranges in pH from about 6.0 to 8.5, and the EPA has published guidelines indicating that the pH of well water should fall between 6.5 and 8.5 because when the pH of water is out of this range it is due to something that may be of concern from a health and safety viewpoint. You really should contact your local water district, even if you are not on a municipal water supply and ask about what is normal in your area.

One real problem with acidic water is plumbing corrosion. The pH of groundwater varies based on the minerals present in the earth and low pH water is not necessarily an indication of a big problem. In fact many regions of the country have low pH and municipal water utilities adjust water pH by adding alkaline solutions, such as sodium hydroxide, to increase the pH to about 8.5. The reason for doing this is to prevent corrosion of pipes caused by acidic water. If your home well water is consistently low your pipes will be damaged over time.

So onto your question about water pH and mashing. The first thing to note about water is its buffering capacity, or its resistance to pH change. All buffers are considered weak acids where an acid component and a base component that are in equilibrium; these two components essentially remove hydrogen and hydroxide ions that are added to a solution and by doing so stabilize changes to pH that would ordinarily be observed when these compounds are added to a poorly buffered solution. The most common buffering system in water is dissolved carbonates and water that contains carbonates will resist changes in pH more than water that has essentially no buffering capacity, for example distilled water.

The second thing to note about pH and brewing is that malt is rich in compounds that are buffers. The two most significant buffering systems added to the mash from malt are phosphates and proteins/polypeptides/amino acids (collectively called “protein”). The buffering capacity of mash is usually much, much higher than water. This means that mash water with a relatively high or relatively low pH may have very little effect on mash pH if the water is poorly buffered. But if the water has a high buffering capacity, as is the case with water high in carbonate, mash pH may end up being higher than desired (high mash is the result of carbonate water).

When brewing water is rich in carbonates the mash pH can be lowered by adding calcium in the form of calcium sulfate and/or calcium chloride to water. When brewing water needs to be adjusted for mash pH control, it is almost always because of carbonates. There are times, however, when the mash pH is too low and needs to be increased. In these cases carbonates are added to water. Calcium carbonate and sodium bicarbonate are two common salts used to increase mash pH, and an example of when these salts may be required are when brewing beers with a high percentage of roasted malts that tend to lower mash pH. Historically, this is why dark beers were brewed in regions with carbonate waters.

Note that in the discussion above I state that calcium salts can be added to mash water to lower mash pH and that carbonates can be added to increase mash pH. It’s the mash pH that is important and in the case of calcium additions the water pH is not altered by the addition because the acidifying effect on mash pH only occurs when calcium reacts with the malt buffer systems.

You need to confirm that you indeed have acidic water, and this may or may not be a concern for your home use. If your water is safe, you should also determine what happens when you use this water for mashing. The simplest and cheapest thing to do is to conduct a small test with about a quarter pound of malt. Just make yourself a small test mash in a pot and measure the pH. It may be that the mash pH is not affected by the water and all will be fine.

If your mash pH is lower than 5.2 and you want to increase your mash pH, you should consider adding sodium bicarbonate (baking soda) or calcium carbonate to your brewing water. These compounds will increase water pH so don’t be surprised if you are measuring water pH as part of your experimentation.

Response by Ashton Lewis.