Water treatment for stout

I live in NYC and the water here is pretty soft
Calcium: 5.5
Sulfates: 4.5
Magnesium: 1.2
Sodium: 8
Chloride: 10
pH: 7.2

What kind of treatment would be advised to balance out all of the roasted malts and low level of salts?

Check out https://sites.google.com/site/brunwater/

There are at least 2 ways to go.  1) Add minerals including an alkalinity increaser such as pickling lime to the mash water and mash the entire grain bill as normal.  2)  Add minerals only to bring the calcium up to a minimum concentration of about 40 to 50 ppm and mash only the base malts in this water.  Steep the crystal and roast malts separately and add their steeping liquid to the boil.  This takes the really acidic grains out of the mash and allows you to avoid the need for adding alkalinity.

Martin…do you recommend treating the brewing water prior to mashing and then adjust pH after doughing in, or would you add your salts to the mash and adjust pH?

By using Bru’n Water, you have some confidence that your brewing water will already be adjusted to produce a proper mash pH.  Or at least you will have a good idea of what pH adjusting minerals or acids you’ll be needing to add to the mash to achieve a desirable pH if you want to check and adjust mash pH as you go.  In the case of using pickling lime, I find that you have to wait and add that mineral after you have doughed in.  It is too strong and increases the water pH too high if added only to the water prior to mash in.    To anyone using pickling lime, you have got to have a scale that has an accuracy of 0.1 grams when you’re dealing with homebrew scale batches.  A scale with 1 gram or worse accuracy may cause you to overdose.  When using lime, underdosing is the way to go if there is any doubt.  Lime’s effect on pH is very strong and that adage “Less is More” is particularly true there.

That’s a good idea. I think I’ve heard of that, but I didn’t know why people steeped those grains separately until now.

I just brewed a stout last weekend. Unfortunately, I learned this lesson of steeping the dark grains after my LHBS milled all the grains together for me. What I did do was monitor the PH during the mash and then added 1/8th teaspoons of calcium carbonate to the mash as needed to keep the PH level close to 5.2-5.4. The beer is still fermenting but I did try to keep my dosing levels low so as not to “over adjust” a common problem I have read from beer judges that hate newbies adding so many PH adjusting chemicals to their beer that it ends up tasting like alka-seltzer.