Topping off fermenter to add volume

When I was a extract Brewer, I routinely added water at the end of the boil from the tap with no problems. No experience with DI water.
I think you will be fine adding w
The water, then the yeast.

 

Why not give it a quick boil just to be safe? Chances are you’ll be fine, but I would probably do a quick boil, just as insurance.
You can add it anytime, shouldn’t make a difference.

 

I think safest bet is distilled water at store. What is your gravity now? For example:

4.5 gallons of 1.068 + 0.5 gallon water

(0.9)(68) + (0.1)(0) = 61.2

Gravity should come out to about 1.061 since 90% of volume is 1.068 and 10% volume is 1.000.

I don’t have any hard data, but I would think adding before fermentation would give a more uniform distribution whereas post fermentation you may dilute beer more. For example if your beer ferments down to 1.014, adding 10% water would theoretically drop you down to 1.012-1.013.

 

If you want to make the beer come out as close as possible to what would have happened if there had not been excess boil-off, add distilled water, and do it before fermentation. Personally, I might boil (and cool) it first to be safe. But I think distilled water would be a very low risk if you decide not to boil.

 

I frequently add 10-15% chilled distilled water at flameout to get to volume and cool beer down at same time.

Have a 6 gallon kettle and only stovetop right now, but I like going into fermenter at 5.5 gallons to try to yield 5 gallons in keg.

 

Interesting. Sounds like a variation of high gravity brewing, but shifting the dilution step to earlier in the process, since your production bottleneck is kettle size rather than fermenter/tank space.

 

As an extract brewer it's routine for me to add boiled/cooled (to room temp) water after the boil, typically around a gallon or so. (Small boil pot.) If I forget and fermentation gets started before I realize it, I resist adding the water until bottling time along with the priming sugar. I just don't want to take a chance interrupting fermentation with the water addition.

 

This is a good point, and one that I agree with. I don't think it's ever a terrific idea to change the playing field (the environment) for the yeast after they have assessed it and done their game planning.

 

As a long time diluter of wort, I have a few pieces of advice:

First, using bottled water is better than fridge water (I used fridge water in one of my first batches with less than ideal results). You can use DO or whatever spring water you want, keeping in mind water chemistry if you want. Bottled is best because it is sanitary without boiling (I use it for every batch and never had it cause an infection) and for those saying “give it a quick boil” are forgetting that getting your volume of water to boiling, holding the boil to kill microbes, and then cooling that water is not really that quick. Plus, what if you undershot the water needed? You’d do it again and take more time. Bottled water is easier and faster and not very expensive. Plus you can refrigerate it to give you that last bit of cooling to pitch temperature 70 to 60.

Second, add the water into the fermenter prior to pitching yeast and before fermentation. There is one major advantage to this over adding down the line. One problem that sometimes comes up with diluting (especially high gravity beer) is that water will not be well mixed and it can lead to stratification and inconsistency throughout the batch. The BEST way to mitigate this is to mix it well when you add water. With that in mind, the closed system of the fermenter with stopper on is the ideal place for a good shake mix. This has the added benefit of oxygenation (if you uncap between shakes to let it breath). The biggest reason this should be done before fermentation is because after this agitation will negatively impact your beer. I think pitching right before or right after this mixing is basically the same, but I do it after so as to ensure all my yeast is in my beer rather than stuck in some nook of my bucket lid.

 

Adding on to what @ssam said, fermentation will do a very good job of mixing the beer to uniformity.

 

One time I brewed a stout, didn't mix the water, and packaged in 12 days. There was a difference in SRM bottle to bottle. I attributed it to an absence of mixing and adjusted my process. Your mileage may vary.

 

I don't doubt your observation. But that would have to be a really tame ale fermentation to not mix all the water/wort. One thing I miss about fermenting in glass carboys is the maelstrom that usually appears.

 

If I remember correctly, this was in 2008-2009 and I used all malt extract and specialty grains for an OG of 1070 and a single vial of liquid yeast. I didn't see vigorous fermentation until 2010 when I started partial mashing and correctly pitching.

 

As a not even newbie but just somebody trying to do as much research before I even try to brew, I have this question that may make it really obvious I've never brewed. But is the only reason to add the water just to add volume? What if you aren't looking for volume and are alright with only having let's say 3.5 gallons. Or does this change everything completely?

 

The reason to add water after the boil is to get to the planned volume, either because more water than anticipated was boiled off or because the kettle/burner wasn't big enough to handle the entire pre-boil volume needed. But it's not the "only" reason, because the volume also affects other properties of the beer.

Using your example, let's say the recipe calls for 5 gallons into the fermenter, but after boiling there are only 3.5 gallons left. That means that the sugars, hop oils, malt flavors etc. are concentrated in only 70% (3.5/5) of the planned wort volume. So there will be about 43% more "stuff" (other than water) per unit volume of wort. If the volume is not topped off, that's going to result in about 43% more alcohol (by volume)... say 7.1% instead of 5%. And the beer is going to be more bitter than planned. And darker. And etc. So yes, it changes everything.

 

In case anyone is interested, this process is called ‘liquoring down’ in pro brewing and is exceedingly common. It is usually done at the beginning or end of the boil. It is done for 3 reasons - 1. To dilute to the proper gravity. 2. To increase to the target volume. 3. To avoid oversparging. Sometimes when brewing a light, low gravity beer, the end of the lauter is pulling shitty, astringent. 1°-2° wort, and you are better off closing the runoff and just topping off with hot liquor.
Along with water chemistry, keep in mind that excessive liquoring down can also affect your pH. Something to keep in mind.

Also, I would never add water post fermentation without special equipment, as the likelihood of introducing oxygen is too high.